Extensible Stylesheet Language (XSL)
Version 1.0

W3C Proposed Recommendation 28 August 2001

This version:

http://www.w3.org/TR/2001/PR-xsl-20010828/
( PDF by RenderX, XML file, HTML (one large file), ZIP file )

Latest version:

http://www.w3.org/TR/xsl/

Previous version:

http://www.w3.org/TR/2000/CR-xsl-20001121/

Authors and Contributors:

Sharon Adler (IBM) <sca@us.ibm.com>
Anders Berglund (IBM) <alrb@us.ibm.com>
Jeff Caruso (Pageflex) <jcaruso@pageflexinc.com>
Stephen Deach (Adobe) <sdeach@adobe.com>
Paul Grosso (Arbortext) <paul@arbortext.com>
Eduardo Gutentag (Sun) <eduardo.gutentag@eng.sun.com>
Alex Milowski <alex@milowski.com>
Scott Parnell (Xerox) <Scott.Parnell@usa.xerox.com>
Jeremy Richman <JeremyRichman@compuserve.com>
Steve Zilles (Adobe) <szilles@adobe.com>

Copyright ©2001 W3C^® (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply.

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Abstract

This specification defines the features and syntax for the Extensible Stylesheet Language (XSL), a language for expressing stylesheets. It consists of two parts:

1. a language for transforming XML documents, and

2. an XML vocabulary for specifying formatting semantics.

An XSL stylesheet specifies the presentation of a class of XML documents by describing how an instance of the class is transformed into an XML document that uses the formatting vocabulary.

Status of this document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this series of documents is maintained at the W3C.

This document is a W3C Proposed Recommendation. This means that the specification is stable and that implementation experience has been gathered showing that the features of the specification can be implemented.

On 28 August 2001, this document enters a Proposed Recommendation review period. From that date until 25 September 2001, W3C Advisory Committee representatives are encouraged to review this specification and return comments to w3t-xsl-review@w3.org.

After the review, the Director will announce the document's disposition: it may become a W3C Recommendation (possibly with minor changes), or it may revert to Working Draft status. This announcement should not be expected sooner than 14 days after the end of the review.

Publication as a Proposed Recommendation does not imply endorsement by the W3C membership. This is still a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite W3C Proposed Recommendations as other than "work in progress". A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR/.

This document has been produced as part of the W3C Style Activity by the XSL Working Group (members only).

Please report errors in this document to xsl-editors@w3.org before the end of the PR review period. Archives of the comments are available. More general public discussion of XSL takes place on the XSL-List mailing list.

Table of contents

Appendices

1 Introduction and Overview

This specification defines the Extensible Stylesheet Language (XSL). XSL is a language for expressing stylesheets. Given a class of arbitrarily structured XML [XML] documents or data files, designers use an XSL stylesheet to express their intentions about how that structured content should be presented; that is, how the source content should be styled, laid out, and paginated onto some presentation medium, such as a window in a Web browser or a hand-held device, or a set of physical pages in a catalog, report, pamphlet, or book.

1.1 Processing a Stylesheet

An XSL stylesheet processor accepts a document or data in XML and an XSL stylesheet and produces the presentation of that XML source content that was intended by the designer of that stylesheet. There are two aspects of this presentation process: first, constructing a result tree from the XML source tree and second, interpreting the result tree to produce formatted results suitable for presentation on a display, on paper, in speech, or onto other media. The first aspect is called tree transformation and the second is called formatting. The process of formatting is performed by the formatter. This formatter may simply be a rendering engine inside a browser.

Tree transformation allows the structure of the result tree to be significantly different from the structure of the source tree. For example, one could add a table-of-contents as a filtered selection of an original source document, or one could rearrange source data into a sorted tabular presentation. In constructing the result tree, the tree transformation process also adds the information necessary to format that result tree.

Formatting is enabled by including formatting semantics in the result tree. Formatting semantics are expressed in terms of a catalog of classes of formatting objects. The nodes of the result tree are formatting objects. The classes of formatting objects denote typographic abstractions such as page, paragraph, table, and so forth. Finer control over the presentation of these abstractions is provided by a set of formatting properties, such as those controlling indents, word- and letter spacing, and widow, orphan, and hyphenation control. In XSL, the classes of formatting objects and formatting properties provide the vocabulary for expressing presentation intent.

The XSL processing model is intended to be conceptual only. An implementation is not mandated to provide these as separate processes. Furthermore, implementations are free to process the source document in any way that produces the same result as if it were processed using the conceptual XSL processing model. A diagram depicting the detailed conceptual model is shown below.

1.1.1 Tree Transformations

Tree transformation constructs the result tree. In XSL, this tree is called the element and attribute tree, with objects primarily in the "formatting object" namespace. In this tree, a formatting object is represented as an XML element, with the properties represented by a set of XML attribute-value pairs. The content of the formatting object is the content of the XML element. Tree transformation is defined in the XSLT Recommendation [XSLT]. A diagram depicting this conceptual process is shown below.

The XSL stylesheet is used in tree transformation. A stylesheet contains a set of tree construction rules. The tree construction rules have two parts: a pattern that is matched against elements in the source tree and a template that constructs a portion of the result tree. This allows a stylesheet to be applicable to a wide class of documents that have similar source tree structures.

In some implementations of XSL/XSLT, the result of tree construction can be output as an XML document. This would allow an XML document which contains formatting objects and formatting properties to be output. This capability is neither necessary for an XSL processor nor is it encouraged. There are, however, cases where this is important, such as a server preparing input for a known client; for example, the way that a WAP (http://www.wapforum.org/faqs/index.htm) server prepares specialized input for a WAP capable hand held device. To preserve accessibility, designers of Web systems should not develop architectures that require (or use) the transmission of documents containing formatting objects and properties unless either the transmitter knows that the client can accept formatting objects and properties or the transmitted document contains a reference to the source document(s) used in the construction of the document with the formatting objects and properties.

1.1.2 Formatting

Formatting interprets the result tree in its formatting object tree form to produce the presentation intended by the designer of the stylesheet from which the XML element and attribute tree in the "fo" namespace was constructed.

The vocabulary of formatting objects supported by XSL - the set of fo: element types - represents the set of typographic abstractions available to the designer. Semantically, each formatting object represents a specification for a part of the pagination, layout, and styling information that will be applied to the content of that formatting object as a result of formatting the whole result tree. Each formatting object class represents a particular kind of formatting behavior. For example, the block formatting object class represents the breaking of the content of a paragraph into lines. Other parts of the specification may come from other formatting objects; for example, the formatting of a paragraph (block formatting object) depends on both the specification of properties on the block formatting object and the specification of the layout structure into which the block is placed by the formatter.

The properties associated with an instance of a formatting object control the formatting of that object. Some of the properties, for example "color", directly specify the formatted result. Other properties, for example 'space-before', only constrain the set of possible formatted results without specifying any particular formatted result. The formatter may make choices among other possible considerations such as esthetics.

Formatting consists of the generation of a tree of geometric areas, called the area tree. The geometric areas are positioned on a sequence of one or more pages (a browser typically uses a single page). Each geometric area has a position on the page, a specification of what to display in that area and may have a background, padding, and borders. For example, formatting a single character generates an area sufficiently large enough to hold the glyph that is used to present the character visually and the glyph is what is displayed in this area. These areas may be nested. For example, the glyph may be positioned within a line, within a block, within a page.

Rendering takes the area tree, the abstract model of the presentation (in terms of pages and their collections of areas), and causes a presentation to appear on the relevant medium, such as a browser window on a computer display screen or sheets of paper. The semantics of rendering are not described in detail in this specification.

The first step in formatting is to "objectify" the element and attribute tree obtained via an XSLT transformation. Objectifying the tree basically consists of turning the elements in the tree into formatting object nodes and the attributes into property specifications. The result of this step is the formatting object tree.

As part of the step of objectifying, the characters that occur in the result tree are replaced by fo:character nodes. Characters in text nodes which consist solely of white space characters and which are children of elements whose corresponding formatting objects do not permit fo:character nodes as children are ignored. Other characters within elements whose corresponding formatting objects do not permit fo:character nodes as children are errors.

The content of the fo:instream-foreign-object is not objectified; instead the object representing the fo:instream-foreign-object element points to the appropriate node in the element and attribute tree. Similarly any non-XSL namespace child element of fo:declarations is not objectified; instead the object representing the fo:declarations element points to the appropriate node in the element and attribute tree.

The second phase in formatting is to refine the formatting object tree to produce the refined formatting object tree. The refinement process handles the mapping from properties to traits. This consists of: (1) shorthand expansion into individual properties, (2) mapping of corresponding properties, (3) determining computed values (may include expression evaluation), (4) handling white-space-treatment and linefeed-treatment property effects, and (5) inheritance. Details on refinement are found in [5 Property Refinement / Resolution].

The refinement step is depicted in the diagram below.

The third step in formatting is the construction of the area tree. The area tree is generated as described in the semantics of each formatting object. The traits applicable to each formatting object class control how the areas are generated. Although every formatting property may be specified on every formatting object, for each formatting object class, only a subset of the formatting properties are used to determine the traits for objects of that class.

Area generation is depicted in the diagram below.

1.2 Benefits of XSL

Unlike the case of HTML, element names in XML have no intrinsic presentation semantics. Absent a stylesheet, a processor could not possibly know how to render the content of an XML document other than as an undifferentiated string of characters. XSL provides a comprehensive model and a vocabulary for writing such stylesheets using XML syntax.

This document is intended for implementors of such XSL processors. Although it can be used as a reference manual for writers of XSL style sheets, it is not tutorial in nature.

XSL builds on the prior work on Cascading Style Sheets [CSS2] and the Document Style Semantics and Specification Language [DSSSL]. While many of XSL's formatting objects and properties correspond to the common set of properties, this would not be sufficient by itself to accomplish all the goals of XSL. In particular, XSL introduces a model for pagination and layout that extends what is currently available and that can in turn be extended, in a straightforward way, to page structures beyond the simple page models described in this specification.

1.2.1 Paging and Scrolling

Doing both scrollable document windows and pagination introduces new complexities to the styling (and pagination) of XML content. Because pagination introduces arbitrary boundaries (pages or regions on pages) on the content, concepts such as the control of spacing at page, region, and block boundaries become extremely important. There are also concepts related to adjusting the spaces between lines (to adjust the page vertically) and between words and letters (to justify the lines of text). These do not always arise with simple scrollable document windows, such as those found in today's browsers. However, there is a correspondence between a page with multiple regions, such as a body, header, footer, and left and right sidebars, and a Web presentation using "frames". The distribution of content into the regions is basically the same in both cases, and XSL handles both cases in an analogous fashion.

XSL was developed to give designers control over the features needed when documents are paginated as well as to provide an equivalent "frame" based structure for browsing on the Web. To achieve this control, XSL has extended the set of formatting objects and formatting properties. In addition, the selection of XML source components that can be styled (elements, attributes, text nodes, comments, and processing instructions) is based on XSLT and XPath [XPath], thus providing the user with an extremely powerful selection mechanism.

The design of the formatting objects and properties extensions was first inspired by DSSSL. The actual extensions, however, do not always look like the DSSSL constructs on which they were based. To either conform more closely with the CSS2 specification or to handle cases more simply than in DSSSL, some extensions have diverged from DSSSL.

There are several ways in which extensions were made. In some cases, it sufficed to add new values, as in the case of those added to reflect a variety of writing-modes, such as top-to-bottom and bottom-to-top, rather than just left-to-right and right-to-left.

In other cases, common properties that are expressed in CSS2 as one property with multiple simultaneous values, are split into several new properties to provide independent control over independent aspects of the property. For example, the "white-space" property was split into four properties: a "white-space-treatment" property that controls how white space is processed, a "linefeed-treatment" property that controls how line feeds are processed, a "white-space-collapse" property that controls how multiple consecutive spaces are collapsed, and a "wrap-option" property that controls whether lines are automatically wrapped when they encounter a boundary, such as the edge of a column. The effect of splitting a property into two or more (sub-)properties is to make the equivalent existing CSS2 property a "shorthand" for the set of sub-properties it subsumes.

In still other cases, it was necessary to create new properties. For example, there are a number of new properties that control how hyphenation is done. These include identifying the script and country the text is from as well as such properties as "hyphenation-character" (which varies from script to script).

Some of the formatting objects and many of the properties in XSL come from the CSS2 specification, ensuring compatibility between the two.

There are four classes of XSL properties that can be identified as:

1. CSS properties by copy (unchanged from their CSS2 semantics)

2. CSS properties with extended values

3. CSS properties broken apart and/or extended

4. XSL-only properties

1.2.2 Selectors and Tree Construction

As mentioned above, XSL uses XSLT and XPath for tree construction and pattern selection, thus providing a high degree of control over how portions of the source content are presented, and what properties are associated with those content portions, even where mixed namespaces are involved.

For example, the patterns of XPath allow the selection of a portion of a string or the Nth text node in a paragraph. This allows users to have a rule that makes all third paragraphs in procedural steps appear in bold, for instance. In addition, properties can be associated with a content portion based on the numeric value of that content portion or attributes on the containing element. This allows one to have a style rule that makes negative values appear in "red" and positive values appear in "black". Also, text can be generated depending on a particular context in the source tree, or portions of the source tree may be presented multiple times with different styles.

1.2.3 An Extended Page Layout Model

There is a set of formatting objects in XSL to describe both the layout structure of a page or "frame" (how big is the body; are there multiple columns; are there headers, footers, or sidebars; how big are these) and the rules by which the XML source content is placed into these "containers".

The layout structure is defined in terms of one or more instances of a "simple-page-master" formatting object. This formatting object allows one to define independently filled regions for the body (with multiple columns), a header, a footer, and sidebars on a page. These simple-page-masters can be used in page sequences that specify in which order the various simple-page-masters shall be used. The page sequence also specifies how styled content is to fill those pages. This model allows one to specify a sequence of simple-page-masters for a book chapter where the page instances are automatically generated by the formatter or an explicit sequence of pages such as used in a magazine layout. Styled content is assigned to the various regions on a page by associating the name of the region with names attached to styled content in the result tree.

In addition to these layout formatting objects and properties, there are properties designed to provide the level of control over formatting that is typical of paginated documents. This includes control over hyphenation, and expanding the control over text that is kept with other text in the same line, column, or on the same page.

1.2.4 A Comprehensive Area Model

The extension of the properties and formatting objects, particularly in the area on control over the spacing of blocks, lines, and page regions and within lines, necessitated an extension of the CSS2 box formatting model. This extended model is described in [4 Area Model] of this specification. The CSS2 box model is a subset of this model. See the mapping of the CSS2 box model terminology to the XSL Area Model terminology in [7.2 XSL Areas and the CSS Box Model]. The area model provides a vocabulary for describing the relationships and space-adjustment between letters, words, lines, and blocks.

1.2.5 Internationalization and Writing-Modes

There are some scripts, in particular in the Far East, that are typically set with words proceeding from top-to-bottom and lines proceeding either from right-to-left (most common) or from left-to-right. Other directions are also used. Properties expressed in terms of a fixed, absolute frame of reference (using top, bottom, left, and right) and which apply only to a notion of words proceeding from left to right or right to left do not generalize well to text written in those scripts.

For this reason XSL (and before it DSSSL) uses a relative frame of reference for the formatting object and property descriptions. Just as the CSS2 frame of reference has four directions (top, bottom, left and right), so does the XSL relative frame of reference have four directions (before, after, start, and end), but these are relative to the "writing-mode". The "writing-mode" property is a way of controlling the directions needed by a formatter to correctly place glyphs, words, lines, blocks, etc. on the page or screen. The "writing-mode" expresses the basic directions noted above. There are writing-modes for "left-to-right - top-to-bottom" (denoted as "lr-tb"), "right-to-left - top-to-bottom" (denoted as "rl-tb"), "top-to-bottom - right-to-left" (denoted as "tb-rl") and more. See [7.27.7 "writing-mode"] for the description of the "writing-mode" property. Typically, the writing-mode value specifies two directions: the first is the inline-progression-direction which determines the direction in which words will be placed and the second is the block-progression-direction which determines the direction in which blocks (and lines) are placed one after another. In addition, the inline-progression-direction for a sequence of characters may be implicitly determined using bidirectional character types for those characters from the Unicode Character Database [UNICODE Character Database] for those characters and the Unicode bidirectional (BIDI) algorithm [UNICODE UAX #9].

Besides the directions that are explicit in the name of the value of the "writing-mode" property, the writing-mode determines other directions needed by the formatter, such as the shift-direction (used for subscripts and superscripts), etc.

1.2.6 Linking

Because XML, unlike HTML, has no built-in semantics, there is no built-in notion of a hypertext link. In this context, "link" refers to "hypertext link" as defined in http://www.w3.org/TR/html401/struct/links.html#h-12.1 as well as some of the aspects of "link" as defined in http://www.w3.org/TR/xlink/#intro, where "link is a relationship between two or more resources or portions of resources, made explicit by an XLink linking element". Therefore, XSL has a formatting object that expresses the dual semantics of formatting the content of the link reference and the semantics of following the link.

XSL provides a few mechanisms for changing the presentation of a link target that is being visited. One of these mechanisms permits indicating the link target as such; another allows for control over the placement of the link target in the viewing area; still another permits some degree of control over the way the link target is displayed in relationship to the originating link anchor.

XSL also provides a general mechanism for changing the way elements are formatted depending on their active state. This is particularly useful in relation to links, to indicate whether a given link reference has already been visited, or to apply a given style depending on whether the mouse, for instance, is hovering over the link reference or not.

2 XSL Transformation

2.1 Tree Construction

The Tree Construction is described in "XSL Transformations" [XSLT].

The provisions in "XSL Transformations" form an integral part of this Recommendation and are considered normative.

2.2 XSL Namespace

The XSL namespace has the URI http://www.w3.org/1999/XSL/Format.

NOTE:

The 1999 in the URI indicates the year in which the URI was allocated by the W3C. It does not indicate the version of XSL being used.

XSL processors must use the XML namespaces mechanism [XML Names] to recognize elements and attributes from this namespace. Elements from the XSL namespace are recognized only in the stylesheet, not in the source document. Implementors must not extend the XSL namespace with additional elements or attributes. Instead, any extension must be in a separate namespace.

This specification uses the prefix fo: for referring to elements in the XSL namespace. However, XSL stylesheets are free to use any prefix, provided that there is a namespace declaration that binds the prefix to the URI of the XSL namespace.

An element from the XSL namespace may have any attribute not from the XSL namespace, provided that the expanded-name of the attribute has a non-null namespace URI. The presence of such attributes must not change the behavior of XSL elements and functions defined in this document. Thus, an XSL processor is always free to ignore such attributes, and must ignore such attributes without giving an error if it does not recognize the namespace URI. Such attributes can provide, for example, unique identifiers, optimization hints, or documentation.

It is an error for an element from the XSL namespace to have attributes with expanded-names that have null namespace URIs (i.e., attributes with unprefixed names) other than attributes defined for the element in this document.

NOTE:

The conventions used for the names of XSL elements, attributes, and functions are as follows: names are all lowercase, hyphens are used to separate words, dots are used to separate names for the components of complex datatypes, and abbreviations are used only if they already appear in the syntax of a related language such as XML or HTML.

3 Introduction to Formatting

The aim of this section is to describe the general process of formatting, enough to read the area model and the formatting object descriptions and properties and to understand the process of refinement.

Formatting is the process of turning the result of an XSL transformation into a tangible form for the reader or listener. This process comprises several steps, some of which depend on others in a non-sequential way. Our model for formatting will be the construction of an area tree, which is an ordered tree containing geometric information for the placement of every glyph, shape, and image in the document, together with information embodying spacing constraints and other rendering information; this information is referred to under the rubric of traits, which are to areas what properties are to formatting objects and attributes are to XML elements. [4 Area Model] will describe the area tree and define the default placement-constraints on stacked areas. However, this is an abstract model which need not be actually implemented in this way in a formatter, so long as the resulting tangible form obeys the implied constraints. Constraints might conflict to the point where it is impossible to satisfy them all. In that case, it is implementation-defined which constraints should be relaxed and in what order to satisfy the others.

Formatting objects are elements in the formatting object tree, whose names are from the XSL namespace; a formatting object belongs to a class of formatting objects identified by its element name. The formatting behavior of each class of formatting objects is described in terms of what areas are created by a formatting object of that class, how the traits of the areas are established, and how the areas are structured hierarchically with respect to areas created by other formatting objects. [6 Formatting Objects] and [7 Formatting Properties] describe formatting objects and their properties.

Some formatting objects are block-level and others are inline-level. This refers to the types of areas which they generate, which in turn refer to their default placement method. Inline-areas (for example, glyph-areas) are collected into lines and the direction in which they are stacked is the inline-progression-direction. Lines are a type of block-area and these are stacked in a direction perpendicular to the inline-progression-direction, called the block-progression-direction. See [4 Area Model] for detailed decriptions of these area types and directions.

In Western writing systems, the block-progression-direction is "top-to-bottom" and the inline-progression-direction is "left-to-right". This specification treats other writing systems as well and introduces the terms "block" and "inline" instead of using absolute indicators like "vertical" and "horizontal". Similarly this specification tries to give relatively-specified directions ("before" and "after" in the block-progression-direction, "start" and "end" in the inline-progression-direction) where appropriate, either in addition to or in place of absolutely-specified directions such as "top", "bottom", "left", and "right". These are interpreted according to the value of the writing-mode property.

Central to this model of formatting is refinement. This is a computational process which finalizes the specification of properties based on the attribute values in the XML result tree. Though the XML result tree and the formatting object tree have very similar structure, it is helpful to think of them as separate conceptual entities. Refinement involves

• propagating the various inherited values of properties (both implicitly and those with an attribute value of "inherit"),

• evaluating expressions in property value specifications into actual values, which are then used to determine the value of the properties,

• converting relative numerics to absolute numerics,

• constructing some composite properties from more than one attribute

Some of these operations (particularly evaluating expressions) depend on knowledge of the area tree. Thus refinement is not necessarily a straightforward, sequential procedure, but may involve look-ahead, back-tracking, or control-splicing with other processes in the formatter. Refinement is described more fully in [5 Property Refinement / Resolution].

To summarize, formatting proceeds by constructing an area tree (containing areas and their traits) which satisfies constraints based on information contained in the XML result tree (containing element nodes and their attributes). Conceptually, there are intermediate steps of constructing a formatting object tree (containing formatting objects and their properties) and refinement; these steps may proceed in an interleaved fashion during the construction of the area tree.

3.1 Conceptual Procedure

This subsection contains a conceptual description of how formatting could work. This conceptual procedure does not mandate any particular algorithms or data structures as long as the result obeys the implied constraints.

The procedure works by processing formatting objects. Each object, while being processed, may initiate processing in other objects. While the objects are hierarchically structured, the processing is not; processing of a given object is rather like a co-routine which may pass control to other processes, but pick up again later where it left off. The procedure starts by initiating the processing of the fo:root formatting object.

Unless otherwise specified, processing a formatting object creates areas and returns them to its parent to be placed in the area tree. Like a co-routine, it resumes control later and initiates formatting of its own children (if any), or some subset of them. The formatting object supplies parameters to its children based on the traits of areas already in the area tree, possibly including areas generated by the formatting object or its ancestors. It then disposes of the areas returned by its formatting object children. It might simply return such an area to its parent (and will always do this if it does not generate areas itself), or alternatively it might arrange the area in the area tree according to the semantics of the formatting object; this may involve changing its geometric position. It terminates processing when all its children have terminated processing (if initiated) and it is finished generating areas.

Some formatting objects do not themselves generate areas; instead these formatting objects simply return the areas returned to them by their children. Alternatively, a formatting object may continue to generate (and return) areas based on information discovered while formatting its own children; for example, the fo:page-sequence formatting object will continue generating pages as long as it contains a flow with unprocessed descendants.

Areas returned to an fo:root formatting object are page-viewport-areas, and are simply placed as children of the area tree root in the order in which they are returned, with no geometrical implications.

As a general rule, the order of the area tree parallels the order of the formatting object tree. That is, if one formatting object precedes another in the depth-first traversal of the formatting object tree, with neither containing the other, then all the areas generated by the first will precede all the areas generated by the second in the depth-first traversal of the area tree, unless otherwise specified. Typical exceptions to this rule would be things like side floats, before floats, and footnotes.

At the end of the procedure, the areas and their traits have been constructed, and they are required to satisfy constraints described in the definitions of their associated formatting objects, and in the area model section. In particular, size and position of the areas will be subject to the placement and spacing constraints described in the area model, unless the formatting object definition indicates otherwise.

The formatting object definitions, property descriptions, and area model are not algorithms. Thus, the formatting object semantics do not specify how the line-breaking algorithm must work in collecting characters into words, positioning words within lines, shifting lines within a container, etc. Rather this specification assumes that the formatter has done these things and describes the constraints which the result is supposed to satisfy.

4 Area Model

In XSL, one creates a tree of formatting objects that serve as inputs or specifications to a formatter. The formatter generates a hierarchical arrangement of areas which comprise the formatted result. This section defines the general model of areas and hoow they interact. The purpose is to present an abstract framework which is used in describing the semantics of formatting objects. It should be seen as describing a series of constraints for conforming implementations, and not as prescribing particular algorithms.

4.1 Introduction

The formatter generates an ordered tree, the area tree, which describes a geometric structuring of the output medium. The terms child, sibling, parent, descendant, and ancestor refer to this tree structure. The tree has a root node.

Each area tree node other than the root is called an area and is associated to a rectangular portion of the output medium. Areas are not formatting objects; rather, a formatting object generates zero or more rectangular areas, and normally each area is generated by a unique object in the formatting object tree.

NOTE:

The only exceptions are when several leaf nodes of the formatting object tree are combined to generate a single area, for example when several characters in sequence generate a single ligature glyph. In all such cases, relevant properties such as font-family and font-size are the same for all the generating formatting objects (see section [4.7.2 Line-building]).

An area has a content-rectangle, the portion in which its child areas are assigned, and optional padding and border. The diagram shows how these portions are related to one another. The outer bound of the border is called the border-rectangle, and the outer bound of the padding is called the padding-rectangle.

Each area has a set of traits, a mapping of names to values, in the way elements have attributes and formatting objects have properties. Individual traits are used either for rendering the area or for defining constraints on the result of formatting, or both. Traits used strictly for formatting purposes or for defining constraints may be called formatting traits, and traits used for rendering may be called rendering traits. Traits whose values are copied or derived from a property of the same or a corresponding name are listed in [C Property Summary] and [5 Property Refinement / Resolution]; other traits are listed below.

NOTE:

Traits are also associated with FOs during the process of refinement. Some traits are assigned during formatting, while others are already present after refinement.

The semantics of each type of formatting object that generates areas are given in terms of which areas it generates and their place in the area-tree hierarchy. This may be further modified by interactions between the various types of formatting objects. The properties of the formatting object determine what areas are generated and how the formatting object's content is distributed among them. (For example, a word that is not to be hyphenated may not have its glyphs distributed into areas on two separate line-areas.)

The traits of an area are either:

directly-derived: the values of directly-derived traits are the computed value of a property of the same or a corresponding name on the generating formatting object, or

indirectly-derived: the values of indirectly-derived traits are the result of a computation involving the computed values of one or more properties on the generating formatting object, other traits on this area or other interacting areas (ancestors, parent, siblings, and/or children) and/or one or more values constructed by the formatter. The calculation formula may depend on the type of the formatting object.

This description assumes that refined values have been computed for all properties of formatting objects in the result tree, i.e., all relative and corresponding values have been computed and the inheritable values have been propagated as described in [5 Property Refinement / Resolution]. This allows the process of inheritance to be described once and avoids a need to repeat information on computing values in this description.

The indirectly-derived traits are: block-progression-direction, inline-progression-direction, shift-direction, glyph-orientation, is-reference-area, is-viewport-area, left-position, right-position, top-position, bottom-position, left-offset, top-offset, is-first, is-last, alignment-point, area-class, start-intrusion-adjustment, end-intrusion-adjustment, generated-by, returned-by, page-number, blink, underline-score, overline-score, through-score, underline-score-color, overline-score-color, through-score-color, alignment-baseline, baseline-shift, nominal-font, dominant-baseline-identifier, actual-baseline-table, and script.

4.2 Rectangular Areas

4.2.1 Area Types

There are two types of areas: block-areas and inline-areas. These differ according to how they are typically stacked by the formatter. An area can have block-area children or inline-area children as determined by the generating formatting object, but a given area's children must all be of one type. Although block-areas and inline-areas are typically stacked, some areas can be explicitly positioned.

A line-area is a special kind of block-area whose children are all inline-areas. A glyph-area is a special kind of inline-area which has no child areas, and has a single glyph image as its content.

Typical examples of areas are: a paragraph rendered by using an fo:block formatting object, which generates block-areas, and a character rendered by using an fo:character formatting object, which generates an inline-area (in fact, a glyph-area).

4.2.2 Common Traits

Associated with any area are two directions, which are derived from the generating formatting object's writing-mode and reference-orientation properties: the block-progression-direction is the direction for stacking block-area descendants of the area, and the inline-progression-direction is the direction for stacking inline-area descendants of the area. Another trait, the shift-direction, is present on inline-areas and refers to the direction in which baseline shifts are applied. Also the glyph-orientation defines the orientation of glyph-images in the rendered result.

If the reference-orientation for an area is 0, then the top, bottom, left, and right edges of the content are parallel to those of the area's parent and consistent with them. Otherwise the edges are rotated from those of the area's parent as described in [7.20.3 "reference-orientation"]. The inline-progression-direction and block-progression-direction are determined by the location of these edges as described in [7.27.7 "writing-mode"].

The Boolean trait is-reference-area determines whether or not an area establishes a coordinate system for specifying indents. An area for which this trait is true is called a reference-area. Only a reference-area may have a block-progression-direction which is different from that of its parent. A reference-area may be either a block-area or an inline-area.

The Boolean trait is-viewport-area determines whether or not an area establishes an opening through which its descendant areas can be viewed, and can be used to present clipped or scrolled material; for example, in printing applications where bleed and trim is desired. An area for which this trait is true is called a viewport-area.

A common construct is a viewport/reference pair. This is a viewport-area V and a block-area reference-area R, where R is the sole child of V and where the start-edge and end-edge of the content-rectangle of R are parallel to the start-edge and end-edge of the content-rectangle of V.

Each area has the traits top-position, bottom-position, left-position, and right-position which represent the distance from the edges of its content-rectangle to the like-named edges of the nearest ancestor reference-area (or the page-viewport-area in the case of areas generated by descendants of formatting objects whose absolute-position is fixed); the left-offset and top-offset determine the amount by which a relatively-positioned area is shifted for rendering. These traits receive their values during the formatting process, or in the case of absolutely positioned areas, during refinement.

The block-progression-dimension and inline-progression-dimension of an area represent the extent of the content-rectangle of that area in each of the two relative dimensions.

Other traits include:

• the is-first and is-last traits, which are Boolean traits indicating the order in which areas are generated and returned by a given formatting object. (See [6.1.1 Definitions Common to Many Formatting Objects]. is-first is true for the first area (or only area) generated and returned by a formatting object, and is-last is true for the last area (or only area));

• the amount of space outside the border-rectangle: space-before, space-after, space-start, and space-end (though some of these may be required to be zero on certain classes of area);

  NOTE:

  "Before", "after", "start", and "end" refer to relative directions and are defined below.

• the thickness of each of the four sides of the padding: padding-before, padding-after, padding-start, and padding-end;

• the style, thickness, and color of each of the four sides of the border: border-before, etc.;

• the background rendering of the area: background-color, background-image, and other background traits; and

• the nominal-font for an area, as determined by the font properties and the character descendants of the area's generating formatting object. (see [5.5.7 Font Properties])

Unless otherwise specified, the traits of a formatting object are present on each of its generated areas, and with the same value. (However, see sections [4.7.2 Line-building] and [4.9.4 Border, Padding, and Background].)

4.2.3 Geometric Definitions

As described above, the content-rectangle is the rectangle bounding the inside of the padding and is used to describe the constraints on the positions of descendant areas. It is possible that marks from descendant glyphs or other areas may appear outside the content-rectangle.

Related to this is the allocation-rectangle of an area, which is used to describe the constraints on the position of the area within its parent area. For an inline-area this is either the normal-allocation-rectangle or the large-allocation-rectangle. The normal-allocation-rectangle extends to the content-rectangle in the block-progression-direction and to the border-rectangle in the inline-progression-direction. The large-allocation-rectangle is the border-rectangle. Unless otherwise specified, the allocation-rectangle for an area is the normal-allocation-rectangle.

For a block-area, the allocation-rectangle extends to the border-rectangle in the block-progression-direction and outside the content-rectangle in the inline-progression-direction by an amount equal to the end-indent, and in the opposite direction by an amount equal to the start-indent.

NOTE:

The inclusion of space outside the border-rectangle of a block-area in the inline-progression-direction does not affect placement constraints, and is intended to promote compatibility with the CSS box model.

The edges of a rectangle are designated as follows:

• the before-edge is the edge occurring first in the block-progression-direction and perpendicular to it;

• the after-edge is the edge opposite the before-edge;

• the start-edge is the edge occurring first in the inline-progression-direction and perpendicular to it,

• the end-edge is the edge opposite the start-edge.

For purposes of this definition, the content-rectangle of an area uses the inline-progression-direction and block-progression-direction of that area; but the border-rectangle, padding-rectangle, and allocation-rectangle use the directions of its parent area. Thus the edges designated for the content-rectangle may not correspond to the same-named edges on the padding-, border-, and allocation-rectangles. This is important in the case of nested block-areas with different writing-modes.

The following diagram shows the correspondence between the various edge names for a mixed writing-mode example:

Each inline-area has an alignment-point determined by the formatter, on the start-edge of its allocation-rectangle; for a glyph-area, this is a point on the start-edge of the glyph on its alignment baseline (see below). This is script-dependent and does not necessarily correspond to the (0,0) coordinate point used for the data describing the glyph shape.

4.2.4 Tree Ordering

In the area tree, the set of areas with a given parent is ordered. The terms initial, final, preceding, and following refer to this ordering.

In any ordered tree, this sibling order extends to an ordering of the entire tree in at least two ways.

• In the pre-order traversal order of a tree, the children of each node (their order unchanged relative to one another) follow the node, but precede any following siblings of the node or of its ancestors.

• In the post-order traversal order of a tree, the children of each node precede the node, but follow any preceding siblings of the node or of its ancestors.

"Preceding" and "following", when applied to non-siblings, will depend on the extension order used, which must be specified. However, in either of these given orders, the leaves of the tree (nodes without children) are unambiguously ordered.

4.2.5 Stacking Constraints

This section defines the notion of block-stacking constraints and inline-stacking constraints involving areas. These are defined as ordered relations, i.e., if A and B have a stacking constraint it does not necessarily mean that B and A have a stacking constraint. These definitions are recursive in nature and some cases may depend upon simpler cases of the same definition. This is not circularity but rather a consequence of recursion. The intention of the definitions is to identify areas at any level of the tree which have only space between them.

The area-class trait is an enumerated value which is xsl-normal for an area which is stacked with other areas in sequence. A normal area is an area for which this trait is xsl-normal. A page-level-out-of-line area is an area with area-class xsl-footnote, xsl-before-float, or xsl-fixed; placement of these areas is controlled by the fo:page-sequence ancestor of its generating formatting object. A reference-level-out-of-line area is an area with area-class xsl-side-float or xsl-absolute; placement of these areas is controlled by the formatting object generating the relevant reference-area. An anchor area is an area with area-class xsl-anchor; placement of these areas is arbitrary and does not affect stacking. Areas with area-class equal to one of xsl-normal, xsl-footnote, or xsl-before-float are defined to be stackable, indicating that they are supposed to be properly stacked.

Block-stacking constraints

If P is a block-area, then there is a fence preceding P if P is a reference-area or if the border-before-width or padding-before-width of P are non-zero. Similarly, there is a fence following P if P is a reference-area or if the border-after-width or padding-after-width of P are non-zero.

If A and B are stackable areas, and S is a sequence of space-specifiers (see [4.3 Spaces and Conditionality]), it is defined that A and B have block-stacking constraint S if any of the following conditions holds:

1. B is a block-area which is the first normal child of A, and S is the sequence consisting of the space-before of B.

2. A is a block-area which is the last normal child of B, and S is the sequence consisting of the space-after of A.

3. A and B are both block-areas, and either

   a. B is the next stackable sibling area of A, and S is the sequence consisting of the space-after of A and the space-before of B;

   b. B is the first normal child of a block-area P, B is not a line-area, there is no fence preceding P, A and P have a block-stacking constraint S', and S consists of S' followed by the space-before of B; or

   c. A is the last normal child of a block-area P, A is not a line-area, there is no fence following P, P and B have a block-stacking constraint S'', and S consists of the space-after of A followed by S''.

   d. A has a block-stacking constraint S' with a block-area E, E has a block-stacking constraint S'' with B, E is empty (i.e., it has zero border, padding, and block-progression-dimension, and no normal children), and S consists of S' followed by S''.

NOTE:

The use of "stackable" in two places in the above definition allows block-stacking constraints to apply between areas of area-class xsl-before-float or xsl-footnote.

When A and B have a block-stacking constraint, the adjacent edges of A and B are an ordered pair recursively defined as:

• In case 1, the before-edge of the content-rectangle of A and the before-edge of the allocation-rectangle of B.

• In case 2, the after-edge of the allocation-rectangle of A and the after-edge of the content-rectangle of B.

• In case 3a, the after-edge of the allocation-rectangle of A and the before-edge of the allocation-rectangle of B.

• In case 3b, the first of the adjacent edges of A and P, and the before-edge of the allocation-rectangle of B.

• In case 3c, the after-edge of the allocation-rectangle of A and the second of the adjacent edges of P and B.

• In case 3d, the first of the adjacent edges of A and E, and the second of the adjacent edges of E and B.

Example. In this diagram each node represents a block-area. Assume that all padding and border widths are zero, and none of the areas are reference-areas. Then P and A have a block-stacking constraint, as do A and B, A and C, B and C, C and D, D and B, B and E, D and E, and E and P; these are the only pairs in the diagram having block-stacking constraints. If B had non-zero padding-after, then D and E would not have any block-stacking constraint (though B and E would continue to have a block-stacking constraint).

Inline-stacking constraints.

This section will recursively define the inline-stacking constraints between two areas (either two inline-areas or one inline-area and one line-area), together with the notion of fence preceding and fence following; these definitions are interwoven with one another. This parallels the definition for block-stacking constraints, but with the additional complication that we may have a stacking constraint between inline-areas which are stacked in opposite inline-progression-directions. (This is not an issue for block-stacking constraints because a block-area which is not a reference-area may not have a block-progression-direction different from that of its parent.)

If P and Q have an inline-stacking constraint, then P has a fence preceding Q if P is a reference-area or has non-zero border-width or padding-width at the first adjacent edge of P and Q. Similarly, Q has a fence following P if Q is a reference-area or has non-zero border-width or padding-width at the second adjacent edge of P and Q.

If A and B are normal areas, and S is a sequence of space-specifiers, it is defined that A and B have inline-stacking constraint S if any of the following conditions holds:

1. A is an inline-area or line-area, B is an inline-area which is the first normal child of A, and S is the sequence consisting of the space-start of B.

2. B is an inline-area or line-area, A is an inline-area which is the last normal child of B, and S is the sequence consisting of the space-end of A.

3. A and B are each either an inline-area or a line-area, and either

   a. both A and B are inline-areas, B is the next normal sibling area of A, and S is the sequence consisting of the space-end of A and the space-start of B;

   b. B is an inline-area which is the first normal child of an inline-area P, P has no fence following A, A and P have an inline-stacking constraint S', the inline-progression-direction of P is the same as the inline-progression-direction of the nearest common ancestor area of A and P, and S consists of S' followed by the space-start of B.

   c. A is an inline-area which is the last normal child of an inline-area P, P has no fence preceding B, P and B have an inline-stacking constraint S'', the inline-progression-direction of P is the same as the inline-progression-direction of the nearest common ancestor area of P and B, and S consists of the space-end of A followed by S''.

   d. B is an inline-area which is the last normal child of an inline-area P, P has no fence following A, A and P have an inline-stacking constraint S', the inline-progression-direction of P is opposite to the inline-progression-direction of the nearest common ancestor area of A and P, and S consists of S' followed by the space-end of B.

   e. A is an inline-area which is the first normal child of an inline-area P, P has no fence preceding B, P and B have an inline-stacking constraint S'', the inline-progression-direction of P is opposite to the inline-progression-direction of the nearest common ancestor area of P and B, and S consists of the space-start of A followed by S''.

When A and B have an inline-stacking constraint, the adjacent edges of A and B are an ordered pair defined as:

• In case 1, the start-edge of the content-rectangle of A and the start-edge of the allocation-rectangle of B.

• In case 2, the end-edge of the allocation-rectangle of A and the end-edge of the content-rectangle of B.

• In case 3a, the end-edge of the allocation-rectangle of A and the start-edge of the allocation-rectangle of B.

• In case 3b, the first of the adjacent edges of A and P, and the start-edge of the allocation-rectangle of B.

• In case 3c, the end-edge of the allocation-rectangle of A and the second of the adjacent edges of P and B.

• In case 3d, the first of the adjacent edges of A and P, and the end-edge of the allocation-rectangle of B.

• In case 3e, the start-edge of the allocation-rectangle of A and the second of the adjacent edges of P and B.

Two areas are adjacent if they have a block-stacking constraint or an inline-stacking constraint. It follows from the definitions that areas of the same type (inline or block) can be adjacent only if all their non-common ancestors are also of the same type (up to but not including their nearest common ancestor). Thus, for example, two inline-areas which reside in different line-areas are never adjacent.

An area A begins an area P if A is a descendant of P and P and A have either a block-stacking constraint or an inline-stacking constraint. In this case the second of the adjacent edges of P and A is defined to be a leading edge in P. A space-specifier which applies to the leading edge is also defined to begin P.

Similarly, An area A ends an area P if A is a descendant of P and A and P have either a block-stacking constraint or an inline-stacking constraint. In this case the first of the adjacent edges of A and P is defined to be a trailing edge in P. A space-specifier which applies to the trailing edge is also defined to end P.

4.2.6 Font Baseline Tables

Each script has its preferred "baseline" for aligning glyphs from that script. Western scripts typically use an "alphabetic" baseline that touches at or near the bottom of capital letters. Further, for each font there is a preferred way of aligning embedded glyphs from different scripts, e.g., for a Western font there are separate baselines for aligning embedded ideographic or Indic glyphs.

Each block-area and inline-area has a dominant-baseline-identifier trait whose value is a baseline identifier corresponding to the type of alignment expected for inline-area descendants of that area, and each inline-area has an alignment-baseline which specifies how the area is aligned to its parent. These traits are interpreted as described in section [7.8.1 Fonts and Font Data].

For each font, an actual-baseline-table maps these identifiers to points on the start-edge of the area. By abuse of terminology, the line in the inline-progression-direction through the point corresponding to the dominant-baseline-identifier is called the "dominant baseline."

4.3 Spaces and Conditionality

A space-specifier is a compound datatype whose components are minimum, optimum, maximum, conditionality, and precedence.

Minimum, optimum, and maximum are lengths and can be used to define a constraint on a distance, namely that the distance should preferably be the optimum, and in any case no less than the minimum nor more than the maximum. Any of these values may be negative, which can (for example) cause areas to overlap, but in any case the minimum should be less than or equal to the optimum value, and the optimum less than or equal to the maximum value.

Conditionality is an enumerated value which controls whether a space-specifier has effect at the beginning or end of a reference-area or a line-area. Possible values are retain and discard; a conditional space-specifier is one for which this value is discard.

Precedence has a value which is either an integer or the special token force. A forcing space-specifier is one for which this value is force.

Space-specifiers occurring in sequence may interact with each other. The constraint imposed by a sequence of space-specifiers is computed by calculating for each space-specifier its associated resolved space-specifier in accordance with their conditionality and precedence, as shown below in the space-resolution rules.

The constraint imposed on a distance by a sequence of resolved space-specifiers is additive; that is, the distance is constrained to be no less than the sum of the resolved minimum values and no larger than the sum of the resolved maximum values.

4.3.1 Space-resolution Rules

To compute the resolved space-specifier of a given space-specifier S, consider the maximal inline-stacking constraint or block-stacking constraint S' containing the space-specifier S as an element of the sequence (S' is a sequence of space-specifiers; see [4.2.5 Stacking Constraints]). The resolved space-specifier of S is a non-conditional, forcing space-specifier computed in terms of this sequence.

1. If any of the space-specifiers in S' is conditional, and begins a reference-area or line-area, then it is suppressed, which means that its resolved space-specifier is zero. Further, any conditional space-specifiers which consecutively follow it in the sequence are also suppressed.

   If a conditional space-specifier ends a reference-area or line-area, then it is suppressed together with any other conditional space-specifiers which consecutively precede it in the sequence.

2. If any of the remaining space-specifiers in S' is forcing, all non-forcing space-specifiers are suppressed, and the value of each of the forcing space-specifiers is taken as its resolved value.

3. Alternatively if all of the remaining space-specifiers in S' are non-forcing, then the resolved space-specifier is defined in terms of those non-suppressed space-specifiers whose precedence is numerically highest, and among these those whose optimum value is the greatest. All other space-specifiers are suppressed. If there is only one of these then its value is taken as its resolved value.

   Otherwise, when there are two or more space-specifiers all of the same highest precedence and the same (largest) optimum, the resolved space-specifier of the last space-specifier in the sequence is derived from these spaces by taking their common optimum value as its optimum, the greatest of their minimum values as its minimum, and the least of their maximum values as its maximum, and all other space-specifiers are suppressed.

4. If S is subject to overconstrainment relaxing, then its maximum value is set to the actual block-progression-dimension of the containing block-area. See [4.3.2 Overconstrained space-specifiers]

Example. Suppose the sequence of space values occurring at the beginning of a reference-area is: first, a space with value 10 points (that is minimum, optimum, and maximum all equal to 10 points) and conditionality discard; second, a space with value 4 points and conditionality retain; and third, a space with value 5 points and conditionality discard; all three spaces having precedence zero. Then the first (10 point) space is suppressed under rule 1, and the second (4 point) space is suppressed under rule 3. The resolved value of the third space is a non-conditional 5 points, even though it originally came from a conditional space.

The padding of a block-area does not interact with any space-specifier (except that by definition, the presence of padding at the before- or after-edge prevents areas on either side of it from having a stacking constraint.)

The border or padding at the before-edge or after-edge of a block-area B may be specified as conditional. If so, then it is set to zero if its associated edge is a leading edge in a reference-area, and the is-first trait of B is false, or if its associated edge is a trailing edge in a reference-area, and the is-last trait of B is false. In either of these cases, the border or padding is taken to be zero for purposes of the stacking constraint definitions.

The border or padding at the start-edge or end-edge of an inline-area I may be specified as conditional. If so, then it is set to zero if its associated edge is a leading edge in a line-area, and the is-first trait of I is false, or if its associated edge is a trailing edge in a line-area, and the is-last trait of I is false. In either of these cases, the border or padding is taken to be zero for purposes of the stacking constraint definitions.

4.3.2 Overconstrained space-specifiers

When an area P is generated by a formatting object whose block-progression-dimension is "auto", then the constraints involving the before-edge and after-edge of the content-rectangle of P, together with the constraints between the various descendants of P, result in a constraint on the actual value of the block-progression-dimension. If the block-progression-dimension is instead specified as a length, then this might result in an overconstrained area tree, for example an incompletely-filled fo:block with a specified size. In that case some constraints between P and its descendants should be relaxed; those that are eligible for this treatment are said to be subject to overconstrainment relaxing, and treated as in the previous section.

• If the display-align value is "after" or "center" and P is the first normal area generated by the formatting object, then the space-before of the first normal child of P is subject to overconstrainment relaxing.

• If the display-align value is "before" or "center" and P is the last normal area generated by the formatting object, then the space-after of the last normal child of P is subject to overconstrainment relaxing.

4.4 Block-areas

Block-areas have several traits which typically affect the placement of their children. The line-height is used in line placement calculations. The line-stacking-strategy trait controls what kind of allocation is used for descendant line-areas and has an enumerated value (either font-height, max-height, or line-height). This is all rigorously described below. All areas have these traits, but they only have relevance for areas which have stacked line-area children.

The space-before and space-after traits determine the distance between the block-area and surrounding block-areas.

A block-area which is not a line-area typically has its size in the inline-progression-direction determined by its start-indent and end-indent and by the size of its nearest ancestor reference-area. A block-area which is not a line-area must be properly stacked (as defined in [4.4.1 Stacked Block-areas] below) unless otherwise specified in the description of its generating formatting object. In this case it its block-progression-dimension will be subject to constraints based on the block-progression-dimensions and space-specifiers of its descendants. See [4.3.2 Overconstrained space-specifiers]

4.4.1 Stacked Block-areas

Block-area children of an area are typically stacked in the block-progression-direction within their parent area, and this is the default method of positioning block-areas. However, formatting objects are free to specify other methods of positioning child areas of areas which they generate, for example list-items or tables.

For a parent area P whose children are block-areas, P is defined to be properly stacked if all of the following conditions hold:

1. For each block-area B which is a descendant of P, the following hold:

   • the before-edge and after-edge of its allocation-rectangle are parallel to the before-edge and after-edges of the content-rectangle of P,

   • the start-edge of its allocation-rectangle is parallel to the start-edge of the content-rectangle of R (where R is the closest ancestor reference-area of B), and offset from it inward by a distance equal to the block-area's start-indent plus its start-intrusion-adjustment (as defined below), minus its border-start, padding-start, and space-start values, and

   • the end-edge of its allocation-rectangle is parallel to the end-edge of the content-rectangle of R, and offset from it inward by a distance equal to the block-area's end-indent plus its end-intrusion-adjustment (as defined below), minus its border-end, padding-end, and space-end values.

   

   NOTE:

   The notion of indent is intended to apply to the content-rectangle, but the constraint is written in terms of the allocation-rectangle, because as noted earlier ([4.2.3 Geometric Definitions]) the edges of the content-rectangle may not correspond to like-named edges of the allocation-rectangle.

   The start-intrusion-adjustment and end-intrusion-adjustment are traits used to deal with intrusions from floats in the inline-progression-direction.

2. For each pair of normal areas B and B' in the subtree below P, if B and B' have a block-stacking constraint S and B is not empty (see [4.2.5 Stacking Constraints]), then the distance between the adjacent edges of B and B' is consistent with the constraint imposed by the resolved values of the space-specifiers in S.

   

   Example. In the diagram, if area A has a space-after value of 3 points, B a space-before of 1 point, and C a space-before of 2 points, all with precedence of force, and with zero border and padding, then the constraints will place B's allocation-rectangle 4 points below that of A, and C's allocation-rectangle 6 points below that of A. Thus the 4-point gap receives the background color from P, and the 2-point gap before C receives the background color from B.

4.4.2 Intrusion Adjustments

Intrusion adjustments (both start- and end-) are defined to account for the indentation that occurs as the result of side floats.

If A and B are areas which have the same nearest reference area ancestor, then A and B are defined to be inline-overlapping if there is some line parallel to the inline-progression-direction, which intersects both the allocation-rectangle of A and the allocation-rectangle of B.

If A is an area of class xsl-side-float with float="start", and B is a block-area, and A and B have the same nearest reference area ancestor, then A is defined to encroach upon B if A and B are inline-overlapping and the start-indent of B is less than the sum of the start-indent of A and the inline-progression-dimension of A. The start-encroachment of A on B is then defined to be amount by which the start-indent of B is less than the sum of the start-indent of A and the inline-progression-dimension of A.

If A is an area of class xsl-side-float with float="end", and B is a block-area, and A and B have the same nearest reference area ancestor, then A is defined to encroach upon B if A and B are inline-overlapping and the end-indent of B is less than the sum of the end-indent of A and the inline-progression-dimension of A. The end-encroachment of A on B is then defined to be amount by which the end-indent of B is less than the sum of the end-indent of A and the inline-progression-dimension of A.

If B is a block-area which is not a line-area, then its local-start-intrusion-adjustment is computed as the maximum of the following lengths:

1. zero;

2. if the parent of B is not a reference area: the start-intrusion-adjustment of the parent of B; and

3. if B has float-displace="block", then for each area A of class xsl-side-float with float="start" such that the generating formatting object of A is not a descendant of the generating formatting object of B, and such that A encroaches upon some line-area child of B: the start-encroachment of A on B; and

4. if B has float-displace = "block", then for each area A of class xsl-side-float with float="start" such that A and B are inline-overlapping, and for each block-area ancestor B' of B which is a descendant of the nearest reference area ancestor of B, such that A encroaches on a line-area child of B': the start-encroachment of A on B'.

The start-intrusion-adjustment of a block-area B is then defined to be the maximum of the local-start-intrusion-adjustments of the normal block-areas generated and returned by the generating formatting object of B.

If L is a line-area, then its start-intrusion-adjustment is computed as the maximum of the following lengths:

1. the start-intrusion-adjustment of the parent of L;

2. for each area A of class xsl-side-float with float="start" such that A encroaches upon L: the start-encroachment of A on L; and

3. if the parent of L has float-displace = "indent", then for each area A of class xsl-side-float with float="start" such that A and L are inline-overlapping, and for each block-area ancestor B' of L which is a descendant of the nearest reference area ancestor of L, such that A encroaches on some line-area child L' of B': the start-encroachment of A on B'.

The end-intrusion-adjustment for a block-area is computed in a precisely analogous manner. That is:

If B is a block-area which is not a line-area, then its local-end-intrusion-adjustment is computed as the maximum of the following lengths:

1. zero;

2. if the parent of B is not a reference area: the end-intrusion-adjustment of the parent of B; and

3. if B has float-displace="block", then for each area A of class xsl-side-float with float="end" such that the generating formatting object of A is not a descendant of the generating formatting object of B, and such that A encroaches upon some line-area child of B: the end-encroachment of A on B; and

4. if B has float-displace = "block", then for each area A of class xsl-side-float with float="end" such that A and B are inline-overlapping, and for each block-area ancestor B' of B which is a descendant of the nearest reference area ancestor of B, such that A encroaches on a line-area child of B': the end-encroachment of A on B'.

The end-intrusion-adjustment of a block-area B is then defined to be the maximum of the local-end-intrusion-adjustments of the normal block-areas generated and returned by the generating formatting object of B.

If L is a line-area, then its end-intrusion-adjustment is computed as the maximum of the following lengths:

1. the end-intrusion-adjustment of the parent of L;

2. for each area A of class xsl-side-float with float="end" such that A encroaches upon L: the end-encroachment of A on L; and

3. if the parent of L has float-displace = "indent", then for each area A of class xsl-side-float with float="end" such that A and L are inline-overlapping, and for each block-area ancestor B' of L which is a descendant of the nearest reference area ancestor of L, such that A encroaches on some line-area child L' of B': the end-encroachment of A on B'.

4.5 Line-areas

A line-area is a special type of block-area, and is generated by the same formatting object which generated its parent. Line-areas do not have borders and padding, i.e., border-before-width, padding-before-width, etc. are all zero. Inline-areas are stacked within a line-area relative to a baseline-start-point which is a point determined by the formatter, on the start-edge of the line area's content-rectangle.

The allocation-rectangle of a line is determined by the value of the line-stacking-strategy trait: if the value is font-height, the allocation-rectangle is the nominal-requested-line-rectangle, defined below; if the value is max-height, the allocation-rectangle is the maximum-line-rectangle, defined below; and if the value is line-height, the allocation-rectangle is the per-inline-height-rectangle, defined below. If the line-stacking-strategy trait is font-height or max-height the space-before and space-after are both set to the half-leading value; otherwise they are both set to zero.

The nominal-requested-line-rectangle for a line-area is the rectangle whose start-edge is parallel to the start-edge of the content-rectangle of the nearest ancestor reference-area and offset from it by the sum of the start-indent and the start-intrusion-adjustment of the line area, whose end-edge is parallel to the end-edge of the content-rectangle of the nearest ancestor reference-area and offset from it by the sum of the end-indent and the end-intrusion-adjustment of the line area, whose before-edge is separated from the baseline-start-point by the text-altitude of the parent block-area, and whose after-edge is separated from the baseline-start-point by the text-depth of the parent block-area. It has the same block-progression-dimension for each line-area child of a block-area.

The maximum-line-rectangle for a line-area is the rectangle whose start-edge and end-edge are parallel to and coincident with the start-edge and end-edge of the nominal-requested-line-rectangle, and whose extent in the block-progression-direction is the minimum required to enclose both the nominal-requested-line-rectangle and the allocation-rectangles of all the inline-areas stacked within the line-area; this may vary depending on the descendants of the line-area.

The per-inline-height-rectangle for a line-area is the rectangle whose start-edge and end-edge are parallel to and coincident with the start-edge and end-edge of the nominal-requested-line-rectangle, and whose extent in the block-progression-dimension is determined as follows.

The expanded-rectangle of an inline-area is the rectangle with start-edge and end-edge coincident with those of its allocation-rectangle, and whose before-edge and after-edge are outside those of its allocation-rectangle by a distance equal to either (a.) the half-leading, when the area's allocation-rectangle is specified to be the normal-allocation-rectangle by the description of the generating formatting object , or (b.) the space-before and space-after (respectively), when the area's allocation-rectangle is specified to be the large-allocation-rectangle. The expanded-nominal-requested-line-rectangle is the rectangle with start-edge and end-edge coincident with those of the nominal-requested-line-rectangle, and whose before-edge and after-edge are outside those of the nominal-requested-line-rectangle by a distance equal to the half-leading.

The extent of the per-inline-height-rectangle in the block-progression-direction is then defined to be the minimum required to enclose both the expanded-nominal-requested-line-rectangle and the expanded-rectangles of all the inline-areas stacked within the line-area; this may vary depending on the descendants of the line-area.

NOTE:

Using the nominal-requested-line-rectangle allows equal baseline-to-baseline spacing. Using the maximum-line-rectangle allows constant space between line-areas. Using the per-inline-height-rectangle and zero space-before and space-after allows CSS-style line box stacking. Also, the value of half-leading is included in the expanded-rectangle regardless of conditionality, and thus a line-height conditionality of "discard" does not have effect in this case.

4.6 Inline-areas

An inline-area has its own line-height trait, which may be different from the line-height of its containing block-area. This may affect the placement of its ancestor line-area when the line-stacking-strategy is line-height. An inline-area has an actual-baseline-table for its nominal-font. It has a dominant-baseline-identifier trait which determines how its stacked inline-area descendants are to be aligned.

An inline-area may or may not have child areas, and if so it may or may not be a reference-area. The dimensions of the content-rectangle for an inline-area without children is computed as specified by the generating formatting object, as are those of an inline-area with block-area children.

An inline-area with inline-area children has a content-rectangle which extends from its dominant baseline (see [4.2.6 Font Baseline Tables]) by its text-depth in the block-progression-direction, and in the opposite direction by its text-altitude; in the inline-progression-direction it extends from the start-edge of the allocation-rectangle of its first child to the end-edge of the allocation-rectangle of its last child. The allocation-rectangle of such an inline-area is the same as its content-rectangle.

The allocation-rectangle of an inline-area without children is either the normal-allocation-rectangle or the large-allocation-rectangle, as specified in the description of the generating formatting object.

NOTE:

When the line-stacking-strategy is line-height, allocation is done with respect to the expanded-rectangle.

Examples of inline-areas with children might include portions of inline mathematical expressions or areas arising from mixed writing systems (left-to-right within right-to-left, for example).

4.6.1 Stacked Inline-areas

Inline-area children of an area are typically stacked in the inline-progression-direction within their parent area, and this is the default method of positioning inline-areas.

Inline-areas are stacked relative to the dominant baseline, as defined above ([4.2.6 Font Baseline Tables]).

For a parent area P whose children are inline-areas, P is defined to be properly stacked if all of the following conditions hold:

1. For each inline-area descendant I of P, the start-edge, end-edge, before-edge and after-edge of the allocation-rectangle of I are parallel to corresponding edges of the content-rectangle of the nearest ancestor reference-area of I.

2. For each pair of normal areas I and I' in the subtree below P, if I and I' have an inline-stacking constraint S, then the distance between the adjacent edges of I and I' is consistent with the constraint imposed by the resolved values of the space-specifiers in S.

3. For any inline-area descendant I of P, the distance in the shift-direction from the dominant baseline of P to the alignment-point of I equals the offset between the dominant baseline of P and the baseline of P corresponding to the alignment-baseline trait of I, plus the sum of the baseline-shifts for I and all of its ancestors which are descendants of P.

   The first summand is computed to compensate for mixed writing systems with different baseline types, and the other summands involve deliberate baseline shifts for things like superscripts and subscripts.

4.6.2 Glyph-areas

The most common inline-area is a glyph-area, which contains the representation for a character (or characters) in a particular font.

A glyph-area has an associated nominal-font, determined by the area's typographic traits, which apply to its character data, and a glyph-orientation determined by its writing-mode and reference-orientation, which determine the orientation of the glyph when it is rendered.

The alignment-point and dominant-baseline-identifier of a glyph-area are assigned according to the writing-system in use (e.g., the glyph baseline in Western languages), and are used to control placement of inline-areas descendants of a line-area. The formatter may generate inline-areas with different inline-progression-directions from their parent to accommodate correct inline-area stacking in the case of mixed writing systems.

A glyph-area has no children. Its block-progression-dimension and actual-baseline-table are the same for all glyphs in a font. Conforming implementations may choose to compute the block-progression-dimension for a glyph area based on the actual glyph size rather than using a common size for all glyphs in a font.

4.7 Ordering Constraints

4.7.1 General Ordering Constraints

A subset S of the areas returned to a formatting object is called properly ordered if the areas in that subset have the same order as their generating formatting objects. Specifically, if A₁ and A₂ are areas in S, returned by child formatting objects F₁ and F₂ where F₁ precedes F₂, then A₁ must precede A₂ in the pre-order traversal order of the area tree. If F₁ equals F₂ and A₁ is returned prior to A₂, then A₁ must precede A₂ in the pre-order-traversal of the area tree.

For each formatting object F and each area-class C, the subset consisting of the areas returned to F with area-class C must be properly ordered, except where otherwise specified.

4.7.2 Line-building

This section describes the ordering constraints that apply to formatting an fo:block or similar block-level object.

A block-level formatting object F which constructs lines does so by constructing block-areas which it returns to its parent formatting object, and placing normal areas and/or anchor areas returned to F by its child formatting objects as children of those block-areas or of line-areas which it constructs as children of those block-areas.

For each such formatting object F, it must be possible to form an ordered partition P consisting of ordered subsets S₁, S₂, ..., S_n of the normal areas and anchor areas returned by the child formatting objects, such that the following are all satisfied:

1. Each subset consists of a sequence of inline-areas, or of a single block-area.

2. The ordering of the partition follows the ordering of the formatting object tree. Specifically, if A is in S_i and B is in S_j with i < j, or if A and B are both in the same subset S_i with A before B in the subset order, then either A is returned by a preceding sibling formatting object of B, or A and B are returned by the same formatting object with A being returned before B.

3. The partitioning occurs at legal line-breaks. Specifically, if A is the last area of S_i and B is the first area of S_i+1, then the rules of the language and script in effect must permit a line-break between A and B, within the context of all areas in S_i and S_i+1.

4. Forced line-breaks are respected. Specifically, if A is the glyph-area generated by a fo:character whose Unicode character is U+000A, then A must be the last area in its containing subset S_i.

5. The partition follows the ordering of the area tree, except for certain glyph substitutions and deletions. Specifically, if B₁, B₂, ..., B_p are the normal child areas of the area or areas returned by F, (ordered in the pre-order traversal order of the area tree) then there is a one-to-one correspondence between these child areas and the partition subsets (i.e., n = p), and for each i,

   • if S_i consists of a single block-area then B_i is that block-area, and

   • if S_i consists of inline-areas then B_i is a line-area whose child areas are the same as the inline-areas in S_i, and in the same order, except that where the rules of the language and script in effect call for glyph-areas to be substituted, inserted, or deleted, then the substituted or inserted glyph-areas appear in the area tree in the corresponding place, and the deleted glyph-areas do not appear in the area tree. Deletions occur when a glyph-area which is last within a subset S_i, has a suppress-at-line-break value of suppress, provided that i < n and B_i+1 is a line-area. Deletions also occur when a glyph-area which is first within a subset S_i, has a suppress-at-line-break value of suppress, provided that i > 1 and B_i-1 is a line-area. Insertions and substitutions may occur because of addition of hyphens or spelling changes due to hyphenation, or glyph image construction from syllabification, or ligature formation.

Substitutions that replace a sequence of glyph-areas with a single glyph-area should only occur when the margin, border, and padding in the inline-progression-direction (start- and end-), baseline-shift, and letter-spacing values are zero, treat-as-word-space is false, and the values of all other relevant traits match (i.e., alignment-adjust, alignment-baseline, color trait, background traits, dominant-baseline-identifier, font traits, text-depth, text-altitude, glyph-orientation-horizontal, glyph-orientation-vertical, line-height, line-height-shift-adjustment, text-decoration, text-shadow).

NOTE:

Line-areas do not receive the background traits or text-decoration of their generating formatting object, or any other trait that requires generation of a mark during rendering.

4.7.3 Inline-building

This section describes the ordering constraints that apply to formatting an fo:inline or similar inline-level object.

An inline-level formatting object F which constructs one or more inline-areas does so by placing normal inline-areas and/or anchor inline-areas returned to F by its child formatting objects as children of inline-areas which it generates.

For each such formatting object F, it must be possible to form an ordered partition P consisting of ordered subsets S₁, S₂, ..., S_n of the normal and/or anchor inline-areas returned by the child formatting objects, such that the following are all satisfied:

1. Each subset consists of a sequence of inline-areas, or of a single block-area.

2. The ordering of the partition follows the ordering of the formatting object tree, as defined above.

3. The partitioning occurs at legal line-breaks, as defined above.

4. Forced line-breaks are respected, as defined above.

5. The partition follows the ordering of the area tree, except for certain glyph substitutions and deletions, as defined above.

4.8 Keeps and Breaks

Keep and break conditions apply to a class of areas, which are typically page-reference-areas, column-areas, and line-areas. The appropriate class for a given condition is referred to as a context and an area in this class is a context-area. As defined in Section [6.4.1 Introduction], page-reference-areas are areas generated by an fo:page-sequence using the specifications in a fo:page-master, and column-areas are normal-flow-reference-areas generated from a region-body, or region-reference-areas generated from other types of region-master.

A keep or break condition is an open statement about a formatting object and the tree relationships of the areas it generates with the relevant context-areas. These tree relationships are defined mainly in terms of leading or trailing areas. If A is a descendant of P, then A is defined to be leading in P if A has no preceding sibling which is a normal area, nor does any of its ancestor areas up to but not including P. Similarly, A is defined to be trailing in P if A has no following sibling which is a normal area, nor does any of its ancestor areas up to but not including P. For any given formatting object, the next formatting object in the flow is the first formatting object following (in the pre-order traversal order) which is not a descendant of the given formatting object and which generates and returns normal areas.

Break conditions are either break-before or break-after conditions. A break-before condition is satisfied if the first area generated and returned by the formatting object is leading within a context-area. A break-after condition depends on the next formatting object in the flow; it is satisfied if either there is no such next formatting object, or if the first normal area generated and returned by that formatting object is leading in a context-area.

Break conditions are imposed by the break-before and break-after properties. A refined value of page for these traits imposes a break condition with a context consisting of the page-reference-areas; a value of even-page or odd-page imposes a break condition with a context of even-numbered page-reference-areas or odd-numbered page-reference-areas, respectively; a value of column imposes a break condition with a context of column-areas. A value of auto in a break-before or break-after trait imposes no break condition.

Keep conditions are either keep-with-previous, keep-with-next, or keep-together conditions. A keep-with-previous condition on an object is satisfied if the first area generated and returned by the formatting object is not leading within a context-area, or if there are no preceding areas in a post-order traversal of the area tree. A keep-with-next condition is satisfied if the last area generated and returned by the formatting object is not trailing within a context-area, or if there are no following areas in a pre-order traversal of the area tree. A keep-together condition is satisfied if all areas generated and returned by the formatting object are descendants of a single context-area.

Keep conditions are imposed by the "within-page", "within-column", and "within-line" components of the "keep-with-previous", "keep-with-next", and "keep-together" properties. The refined value of each component specifies the strength of the keep condition imposed, with higher numbers being stronger than lower numbers and the value always being stronger than all numeric values. A component with value auto does not impose a keep condition. A "within-page" component imposes a keep-condition with context consisting of the page-reference-areas; "within-column", with context consisting of the column-areas; and "within-line" with context consisting of the line-areas.

The area tree is constrained to satisfy all break conditions imposed. Each keep condition must also be satisfied, except when this would cause a break condition or a stronger keep condition to fail to be satisfied. If not all of a set of keep conditions of equal strength can be satisfied, then some maximal satisfiable subset of conditions of that strength must be satisfied (together with all break conditions and maximal subsets of stronger keep conditions, if any).

4.9 Rendering Model

This section makes explicit the relationship between the area tree and visually rendered output.

Areas generate three types of marks: (1) the area background, if any, (2) the marks intrinsic to the area (a glyph, image, or decoration) if any, and (3) the area border, if any.

An area tree is rendered by causing marks to appear on an output medium in accordance with the areas in the area tree. This section describes the geometric location of such marks, and how conflicts between marks are to be resolved.

4.9.1 Geometry

Each area is rendered in a particular location. Formatting object semantics describe the location of intrinsic marks relative to the object's location, i.e., the left, right, top, and bottom edges of its content-rectangle. This section describes how the area's location is determined, which determines the location of its intrinsic marks.

For each page, the page-viewport-area corresponds isometrically to the output medium.

The page-reference-area is offset from the page-viewport-area as described below in section [4.9.2 Viewport Geometry].

All areas in the tree with an area-class of xsl-fixed are positioned such that the left-, right-, top-, and bottom-edges of its content-rectangle are offset inward from the content-rectangle of its ancestor page-viewport-area by distances specified by the left-position, right-position, top-position, and bottom-position traits, respectively.

Any area in the tree which is the child of a viewport-area is rendered as described in section [4.9.2 Viewport Geometry].

All other areas in the tree are positioned such that the left-, right-, top-, and bottom-edges of its content-rectangle are offset inward from the content-rectangle of its nearest ancestor reference-area by distances specified by the left-position, right-position, top-position, and bottom-position traits, respectively. These are shifted down and left by the values of the top-offset and left-offset traits, respectively, if the area has a relative-position of relative.

4.9.2 Viewport Geometry

A reference-area which is the child of a viewport-area is positioned such that the start-edge and end-edge of its content-rectangle are parallel to the start-edge and end-edge of the content-rectangle of its parent viewport-area. The start-edge of its content-rectangle is offset from the start-edge of the content-rectangle of its parent viewport-area by an inline-scroll-amount, and the before-edge of its content-rectangle is offset from the before-edge of the content-rectangle of its parent viewport-area by a block-scroll-amount.

If the block-progression-dimension of the reference-area is larger than that of the viewport-area and the overflow trait for the reference-area is scroll, then the inline-scroll-amount and block-scroll-amount are determined by a scrolling mechanism, if any, provided by the user agent. Otherwise, both are zero.

4.9.3 Visibility

The visibility of marks depends upon the location of the marks, the visibility of the area, and the overflow of any ancestor viewport-areas.

If an area has visibility hidden it generates no marks.

If an area has an overflow of hidden, or when the environment is non-dynamic and the overflow is scroll then the area determines a clipping rectangle, which is defined to be the rectangle determined by the value of the clip trait of the area, and for any mark generated by one of its descendant areas, portions of the mark lying outside the clipping rectangle do not appear.

4.9.4 Border, Padding, and Background

The border- and padding-rectangles are determined relative to the content-rectangle by the values of the common padding and border width traits (border-before-width, etc.).

For any area, which is not a child of a viewport-area, the border is rendered between the border-rectangle and the padding-rectangle in accordance with the common border color and style traits. For a child of a viewport-area, the border is not rendered.

For an area, which is not part of a viewport/reference pair, the background is rendered. For an area that is either a viewport-area or a reference-area in a viewport/reference pair, if the refined value of background-attachment is scroll and the block-progression-dimension of the reference-area is larger than that of the viewport-area, then the background is rendered on the reference-area and not the viewport-area, and otherwise it is rendered on the viewport-area and not the reference-area.

The background, if any, is rendered in the padding-rectangle, in accordance with the background-image, background-color, background-repeat, background-position-vertical, and background-position-horizontal traits.

4.9.5 Intrinsic Marks

For each class of formatting objects, the marks intrinsic to its generated areas are specified in the formatting object description. For example, an fo:character object generates a glyph-area, and this is rendered by drawing a glyph within that area's content-rectangle in accordance with the area's font traits and glyph-orientation and blink traits.

In addition, other traits (for example the various score and score-color traits) specify other intrinsic marks. In the case of score traits (underline-score, overline-score and through-score), the score thickness and position are specified by the nominal-font in effect; where the font fails to specify these quantities, they are implementation-dependent.

4.9.6 Layering and Conflict of Marks

Marks are layered as described below, which defines a partial ordering of which marks are beneath which other marks.

Two marks are defined to conflict if they apply to the same point in the output medium. When two marks conflict, the one which is beneath the other does not affect points in the output medium where they both apply.

Marks generated by the same area are layered as follows: the area background is beneath the area's intrinsic marks, and the intrinsic marks are beneath the border. Layering among the area's intrinsic marks is defined by the semantics of the area's generating formatting object and its properties. For example, a glyph-area's glyph drawing comes beneath the marks generated for text-decoration.

The stacking layer of an area is defined by its stacking context and its z-index value. The stacking layer of an area A is defined to be less than that of an area B if some ancestor-or-self A' of A and B' of B have the same stacking context and the z-index of A' is less than the z-index of B'. If neither stacking layer is less than the other then they are defined to have the same stacking layer.

If A and B are areas, and the stacking layer of A is less than the stacking layer of B, then all marks generated by A are beneath all marks generated by B.

If A and B are areas with the same stacking layer, the backgrounds of A and B come beneath all other marks generated by A and B. Further, if A is an ancestor of B (still with the same stacking layer), then the background of A is beneath all the areas of B, and all the areas of B are beneath the intrinsic areas (and border) of A.

If A and B have the same stacking layer and neither is an ancestor of the other, then it is an error if either their backgrounds conflict or if a non-background mark of A conflicts with a non-background mark of B. An implementation may recover by proceeding as if the marks from the first area in the pre-order traversal order are beneath those of the other area.

4.10 Sample Area Tree

5 Property Refinement / Resolution

During refinement the set of properties that apply to a formatting object is transformed into a set of traits that define constraints on the result of formatting. For many traits there is a one-to-one correspondence with a property; for other traits the transformation is more complex. Details on the transformation are described below.

The first step in refinement of a particular formatting object is to obtain the effective value of each property that applies to the object. Any shorthand property specified on the formatting object is expanded into the individual properties. This is further described in [5.2 Shorthand Expansion]. For any property that has not been specified on the object the inherited (see [5.1.4 Inheritance]) or initial value, as applicable, is used as the effective value. The second step is to transform this property set into traits.

NOTE:

Although the refinement process is described in a series of steps, this is solely for the convenience of exposition and does not imply they must be implemented as separate steps in any conforming implementation. A conforming implementation must only achieve the same effect.

5.1 Specified, Computed, and Actual Values, and Inheritance

For every property that is applicable to a given formatting object, it is necessary to determine the value of the property. Three variants of the property value are distinguished: the specified value, the computed value, and the actual value. The "specified value" is one that is placed on the formatting object during the tree-construction process. A specified value may not be in a form that is directly usable; for example, it may be a percentage or other expression that must be converted into an absolute value. A value resulting from such a conversion is called the "computed value". Finally, the computed value may not be realizable on the output medium and may need to be adjusted prior to use in rendering. For example, a line width may be adjusted to become an integral number of output medium pixels. This adjusted value is the "actual value."

5.1.1 Specified Values

The specified value of a property is determined using the following mechanisms (in order of precedence):

1. If the tree-construction process placed the property on the formatting object, use the value of that property as the specified value. This is called "explicit specification".

2. Otherwise, if the property is inheritable, use the value of that property from the parent formatting object, generally the computed value (see below).

3. Otherwise use the property's initial value, if it has one. The initial value of each property is indicated in the property's definition. If there is no initial value, that property is not specified on the formatting object. In general, this is an error.

Since it has no parent, the root of the result tree cannot use values from its parent formatting object; in this case, the initial value is used if necessary.

5.1.2 Computed Values

Specified values may be absolute (i.e., they are not specified relative to another value, as in "red" or "2mm") or relative (i.e., they are specified relative to another value, as in "auto", "2em", and "12%"), or they may be expressions. For most absolute values, no computation is needed to find the computed value. Relative values, on the other hand, must be transformed into computed values: percentages must be multiplied by a reference value (each property defines which value that is), values with a relative unit (em) must be made absolute by multiplying with the appropriate font size, "auto" values must be computed by the formulas given with each property, certain property values ("smaller", "bolder") must be replaced according to their definitions. The computed value of any property that controls a border width where the style of the border is "none" is forced to be "0pt".

Some properties have more than one way in which the property value can be specified. The simplest example of such properties are those which can be specified either in terms of a direction relative to the writing-mode (e.g., padding-before) or a direction in terms of the absolute geometric orientation of the viewport (e.g., padding-top). These two properties are called the relative property and the absolute property, respectively. Collectively, they are called "corresponding properties".

Specifying a value for one property determines both a computed value for the specified property and a computed value for the corresponding property. Which relative property corresponds to which absolute property depends on the writing-mode. For example, if the "writing-mode" at the top level of a document is "lr-tb", then "padding-start" corresponds to "padding-left", but if the "writing-mode" is "rl-tb", then "padding-start" corresponds to "padding-right". The exact specification of how to compute the values of corresponding properties is given in [5.3 Computing the Values of Corresponding Properties].

In most cases, elements inherit computed values. However, there are some properties whose specified value may be inherited (e.g., some values for the "line-height" property). In the cases where child elements do not inherit the computed value, this is described in the property definition.

5.1.3 Actual Values

A computed value is in principle ready to be used, but a user agent may not be able to make use of the value in a given environment. For example, a user agent may only be able to render borders with integer pixel widths and may, therefore, have to adjust the computed width to an integral number of media pixels. The actual value is the computed value after any such adjustments have been applied.

5.1.4 Inheritance

Some of the properties applicable to formatting objects are "inheritable." Such properties are so identified in the property description. The inheritable properties can be placed on any formatting object. The inheritable properties are propagated down the formatting object tree from a parent to each child. (These properties are given their initial value at the root of the result tree.) For a given inheritable property, if that property is present on a child, then that value of the property is used for that child (and its descendants until explicitly re-set in a lower descendant); otherwise, the specified value of that property on the child is the computed value of that property on the parent formatting object. Hence there is always a specified value defined for every inheritable property for every formatting object.

5.2 Shorthand Expansion

In XSL there are two kinds of shorthand properties; those originating from CSS, such as "border", and those that arise from breaking apart and/or combining CSS properties, such as "page-break-inside". In XSL both types of shorthands are handled in the same way.

NOTE:

Shorthands are only included in the highest XSL conformance level: "complete" (see [8 Conformance]).

The conformance level for each property is shown in [C.3 Property Table: Part II].

Shorthand properties do not inherit from the shorthand on the parent. Instead the individual properties that the shorthand expands into may inherit.

Some CSS shorthands are interrelated; their expansion has one or more individual properties in common. CSS indicates that the user must specify the order of processing for combinations of multiple interrelated shorthands and individual interrelated properties. In XML, attributes are defined as unordered. To resolve this issue, XSL defines a precedence order when multiple interrelated shorthand properties or a shorthand property and an interrelated individual property are specified:

They are processed in increasing precision (i.e., "border" is less precise than "border-top", which is less precise than "border-top-color"). The individual properties are always more precise than any shorthand. For the remaining ambiguous case, XSL defines the ordering to be:

1. "border-style", "border-color", and "border-width" is less precise than

2. "border-top", "border-bottom", "border-right", and "border-left".

Processing is conceptually in the following steps:

1. Set the effective value of all properties to their initial values.

2. Process all shorthands in increasing precision.

   If the shorthand is set to "inherit": set the effective value of each property that can be set by the shorthand to the computed value of the corresponding property in the parent.

   If the value of the shorthand is not "inherit": determine which individual properties are to be set, and replace the initial value with the computed value derived from the specified value.

3. Process all specified individual properties.

4. Carry out any inheritance for properties that were not given a value other than by the first step.

NOTE:

For example, if both the "background" and the "background-color" properties are specified on a given formatting object: process the "background" shorthand, then process the "background-color" property.

5.3 Computing the Values of Corresponding Properties

Where there are corresponding properties, such as "padding-left" and "padding-start", a computed value is determined for all the corresponding properties. How the computed values are determined for a given formatting object is dependent on which of the corresponding properties are specified on the object. See description below.

The correspondence mapping from absolute to relative property is as follows:

If the "writing-mode" specifies a block-progression-direction of "top-to-bottom": "top" maps to "before", and "bottom" maps to "after".

If the "writing-mode" specifies a block-progression-direction of "bottom-to-top": "top" maps to "after", and "bottom" maps to "before".

If the "writing-mode" specifies a block-progression-direction of "left-to-right": "left" maps to "before", and "right" maps to "after".

If the "writing-mode" specifies a block-progression-direction of "right-to-left": "left" maps to "after", and "right" maps to "before".

If the "writing-mode" specifies an inline-progression-direction of "left-to-right": "left" maps to "start", and "right" maps to "end".

If the "writing-mode" specifies an inline-progression-direction of "right-to-left": "left" maps to "end", and "right" maps to "start".

If the "writing-mode" specifies an inline-progression-direction of "top-to-bottom": "top" maps to "start", and "bottom" maps to "end".

If the "writing-mode" specifies an inline-progression-direction of "bottom-to-top": "top" maps to "end", and "bottom" maps to "start".

If the "writing-mode" specifies an inline-progression-direction of "left-to-right" for odd-numbered lines, and "right-to-left" for even-numbered lines: "left" maps to "start", and "right" maps to "end".

NOTE:

"reference-orientation" is a rotation and does not influence the correspondence mapping.

5.3.1 Border and Padding Properties

The simplest class of corresponding properties are those for which there are only two variants in the correspondence, an absolute property and a relative property, and the property names differ only in the choice of absolute or relative designation; for example, "border-left-color" and "border-start-color".

For this class, the computed values of the corresponding properties are determined as follows. If the corresponding absolute variant of the property is specified on the formatting object, its computed value is used to set the computed value of the corresponding relative property. If the corresponding absolute property is not explicitly specified, then the computed value of the absolute property is set to the computed value of the corresponding relative property. If the corresponding relative property is specified on the formatting object and the absolute property only specified by the expansion of a shorthand, then the computed value of the absolute property is set to the computed value of the corresponding relative property.

Note that if both the absolute and the relative properties are not explicitly specified, then the rules for determining the specified value will use either inheritance if that is defined for the property or the initial value. The initial value must be the same for all possible corresponding properties. If both an absolute and a corresponding relative property are explicitly specified, then the above rule gives precedence to the absolute property, and the specified value of the corresponding relative property is ignored in determining the computed value of the corresponding properties.

The (corresponding) properties that use the above rule to determine their computed value are:

• border-after-color

• border-before-color

• border-end-color

• border-start-color

• border-after-style

• border-before-style

• border-end-style

• border-start-style

• border-after-width

• border-before-width

• border-end-width

• border-start-width

• padding-after

• padding-before

• padding-end

• padding-start

5.3.2 Margin, Space, and Indent Properties

The "space-before", and "space-after" properties (block-level formatting objects), "space-start", and "space-end" properties (inline-level formatting objects) are handled in the same way as the properties immediately above, but the corresponding absolute properties are in the set: "margin-top", "margin-bottom", "margin-left", and "margin-right". The .conditionality component of any space-before or space-after determined from a margin property is set to "retain".

NOTE:

The treatment of the .conditionality component is for CSS2 compatibility.

NOTE:

The computed value of a CSS2 margin in the block-progression-dimension specified as "auto" is 0pt. Any space-before or space-after determined from a margin value of "auto" is set to 0pt.

There are two more properties, "end-indent" and "start-indent" (block-level formatting objects) which correspond to the various absolute "margin" properties. For these properties, the correspondence is more complex and involves the corresponding "border-X-width" and "padding-X" properties, where X is one of "left", "right", "top" or "bottom". The computed values of these corresponding properties are determined as follows:

If the corresponding absolute "margin" property is specified on the formatting object and the formatting object generates a reference area the computed value of the margin is used to calculate the computed value of the corresponding "Y-indent" property, where Y is either "start" or "end". The formulae for "start-indent" and "end-indent" are":

start-indent = margin-corresponding + padding-corresponding + border-corresponding-width

end-indent = margin-corresponding + padding-corresponding + border-corresponding-width

If the corresponding absolute "margin" property is specified on the formatting object and the formatting object does not generate a reference area, the computed value of the margin and the computed values of the corresponding "border-X-width" and "padding-X" properties are used to calculate the computed value of the corresponding "Y-indent" property. The formulae for "start-indent" and "end-indent" are:

start-indent = inherited_value_of(start-indent) + margin-corresponding + padding-corresponding + border-corresponding-width

end-indent = inherited_value_of(end-indent) + margin-corresponding + padding-corresponding + border-corresponding-width

If the corresponding absolute margin property is not explicitly specified, or if the corresponding relative property is specified on the formatting object and the absolute property only specified by the expansion of a shorthand, the corresponding absolute margin property is calculated according to the following formulae:

margin-corresponding = start-indent - inherited_value_of(start-indent) - padding-corresponding - border-corresponding-width

margin-corresponding = end-indent - inherited_value_of(end-indent) - padding-corresponding - border-corresponding-width

NOTE:

If the "start-indent" or "end-indent" properties are not specified their inherited value is used in these formulae.

5.3.3 Height, and Width Properties

Based on the writing-mode in effect for the formatting object, either the "height", "min-height", and "max-height" properties, or the "width", "min-width", and "max-width" properties are converted to the corresponding block-progression-dimension, or inline-progression-dimension.

The "height" properties are absolute and indicate the dimension from "top" to "bottom"; the width properties the dimension from "left" to "right".

If the "writing-mode" specifies a block-progression-direction of "top-to-bottom" or "bottom-to-top" the conversion is as follows:

• If any of "height", "min-height", or "max-height" is specified:

  • If "height" is specified then first set:

    block-progression-dimension.minimum=<height>

    block-progression-dimension.optimum=<height>

    block-progression-dimension.maximum=<height>

  • If "height" is not specified, then first set:

    block-progression-dimension.minimum=auto

    block-progression-dimension.optimum=auto

    block-progression-dimension.maximum=auto

  • Then, if "min-height" is specified, reset:

    block-progression-dimension.minimum=<min-height>

  • Then, if "max-height" is specified, reset:

    block-progression-dimension.maximum=<max-height>

  • However, if "max-height" is specified as "none", reset:

    block-progression-dimension.maximum=auto

• If any of "width", "min-width", or "min-width" is specified:

  • If "width" is specified then first set:

    inline-progression-dimension.minimum=<width>

    inline-progression-dimension.optimum=<width>

    inline-progression-dimension.maximum=<width>

  • If "width" is not specified, then first set:

    inline-progression-dimension.minimum=auto

    inline-progression-dimension.optimum=auto

    inline-progression-dimension.maximum=auto

  • Then, if "min-width" is specified, reset:

    inline-progression-dimension.minimum=<min-width>

  • Then, if "max-width" is specified, reset:

    inline-progression-dimension.maximum=<max-width>

  • However, if "max-width" is specified as "none", reset:

    inline-progression-dimension.maximum=auto

If the "writing-mode" specifies a block-progression-direction of "left-to-right" or "right-to-left" the conversion is as follows:

• If any of "height", "min-height", or "max-height" is specified:

  • If "height" is specified then first set:

    inline-progression-dimension.minimum=<height>

    inline-progression-dimension.optimum=<height>

    inline-progression-dimension.maximum=<height>

  • If "height" is not specified, then first set:

    inline-progression-dimension.minimum=auto

    inline-progression-dimension.optimum=auto

    inline-progression-dimension.maximum=auto

  • Then, if "min-height" is specified, reset:

    inline-progression-dimension.minimum=<min-height>

  • Then, if "max-height" is specified, reset:

    inline-progression-dimension.maximum=<max-height>

  • However, if "max-height" is specified as "none", reset:

    inline-progression-dimension.maximum=auto

• If any of "width", "min-width", or "min-width" is specified:

  • If "width" is specified then first set:

    block-progression-dimension.minimum=<width>

    block-progression-dimension.optimum=<width>

    block-progression-dimension.maximum=<width>

  • If "width" is not specified, then first set:

    block-progression-dimension.minimum=auto

    block-progression-dimension.optimum=auto

    block-progression-dimension.maximum=auto

  • Then, if "min-width" is specified, reset:

    block-progression-dimension.minimum=<min-width>

  • Then, if "max-width" is specified, reset:

    block-progression-dimension.maximum=<max-width>

  • However, if "max-width" is specified as "none", reset:

    block-progression-dimension.maximum=auto

5.3.4 Overconstrained Geometry

The sum of the start-indent, end-indent, and inline-progression-dimension of the content-rectangle of an area should be equal to the inline-progression-dimension of the content-rectangle of the closest ancestor reference-area. In the case where a specification would lead to them being different the end-indent (and thus the corresponding margin) is adjusted such that the equality is true.

5.4 Simple Property to Trait Mapping

The majority of the properties map into traits of the same name. Most of these also simply copy the value from the property. These are classified as "Rendering", "Formatting", "Specification", "Font selection", "Reference", and "Action" in the property table in [C.3 Property Table: Part II]. For example, the property font-style="italic" is refined into a font-style trait with a value of "italic".

Some traits have a value that is different from the value of the property. These are classified as "Value change" in the property table. For example, the property background-position-horizontal="left" is refined into a background-position-horizontal trait with a value of "0pt". The value mapping for these traits is given below.

5.4.1 Background-position-horizontal and background-position-vertical Properties

A value of "top", "bottom", "left", "right", or "center" is converted to a length as specified in the property definition.

5.4.2 Column-number Property

If a value has not been specified on a formatting object to which this property applies the initial value is computed as specified in the property definition.

5.4.3 Text-align Property

A value of "left", or "right" is converted to the writing-mode relative value as specified in the property definition.

5.4.4 Text-align-last Property

A value of "left", or "right" is converted to the writing-mode relative value as specified in the property definition.

5.4.5 z-index Property

The value is converted to one that is absolute; i.e., the refined value is the specified value plus the refined value of z-index of its parent formatting object, if any.

5.5 Complex Property to Trait Mapping

A small number of properties influence traits in a more complex manner. Details are given below.

5.5.1 Word spacing and Letter spacing Properties

These properties may set values for the start-space and end-space traits, as described in the property definitions.

5.5.2 Reference-orientation Property

The reference-orientation trait is copied from the reference-orientation property during refinement. During composition an absolute orientation is determined (see [4.2.2 Common Traits]).

5.5.3 Writing-mode and Direction Properties

The writing-mode, direction, and unicode-bidi traits are copied from the properties of the same name during refinement. During composition these are used in the determination of absolute orientations for the block-progression-direction, inline-progression-direction, and shift-direction traits in accordance with [4.2.2 Common Traits].

5.5.4 Absolute-position Property

If absolute-position = "absolute" or "fixed", the values of the left-position, top-position, etc. traits are copied directly from the values of the "left", "top", etc. properties. Otherwise these traits' values are left undefined during refinement and determined during composition.

5.5.5 Relative-position Property

If relative-position = "relative" then the values of the left-offset and top-offset traits are copied directly from the "left" and "top" properties. If the "right" property is specified but "left" is not, then left-offset is set to the negative of the value of "right". If neither "left" nor "right" is specified the left-offset is 0. If the "bottom" property is specified but "top" is not, then top-offset is set to the negative of the value of "bottom". If neither "top" nor "bottom" is specified the top-offset is 0.

5.5.6 Text-decoration Property

The "text-decoration" property value provides values for the blink trait and a set of score and score-color traits. The specified color has the value of the color trait of the formatting object for which the "text-decoration" property is being refined.

A property value containing the token "underline" sets a value of "true" to the underline-score trait, and a value of specified color to the underline-score-color trait.

A property value containing the token "overline" sets a value of "true" to the overline-score trait, and a value of specified color to the overline-score-color trait.

A property value containing the token "line-through" sets a value of "true" to the through-score trait, and a value of specified color to the through-score-color trait.

A property value containing the token "blink" sets a value of "true" to the blink trait.

A property value containing the token "no-underline" sets a value of "false" to the underline-score trait, and a value of specified color to the underline-score-color trait.

A property value containing the token "no-overline" sets a value of "false" to the overline-score trait, and a value of specified color to the overline-score-color trait.

A property value containing the token "no-line-through" sets a value of "false" to the through-score trait, and a value of specified color to the through-score-color trait.

A property value containing the token "no-blink" sets a value of "false" to the blink trait.

5.5.7 Font Properties

The font traits on an area are indirectly derived from the combination of the font properties, which are used to select a font, and the font tables from that font.

The abstract model that XSL assumes for a font is described in [7.8.1 Fonts and Font Data].

There is no XSL mechanism to specify a particular font; instead, a selected font is chosen from the fonts available to the User Agent based on a set of selection criteria. The selection criteria are the following font properties: "font-family", "font-style", "font-variant", "font-weight", "font-stretch", and "font-size", plus, for some formatting objects, one or more characters. The details of how the selection criteria are used is specified in the "font-selection-strategy" property (see [7.8.3 "font-selection-strategy"]).

The nominal-font trait is set to the selected font. In the case where there is no selected font and the 'missing character' glyph is displayed, the nominal-font trait is set to the font containing that glyph, otherwise (i.e., some other mechanism was used to indicate that a character is not being displayed) the nominal-font is a system font.

The dominant-baseline-identifier and actual-baseline-table traits are derived from the value of the "dominant-baseline" property. The value of this property is a compound value with three components: a baseline-identifier for the dominant-baseline, a baseline-table and a baseline-table font-size. The dominant-baseline-identifier is set from the first component. The baseline-table font-size is used to scale the the positions of the baselines from the baseline table and, then, the position of the dominant-baseline is subtracted from the positions of the other baselines to yield a table of offsets from the dominant baseline. This table is the value of the actual-baseline-table trait.

5.6 Non-property Based Trait Generation

The is-reference-area trait is set to "true" for the following formatting objects: "simple-page-master", "title", "region-body", "region-before","region-after", "region-start", "region-end", "block-container", "inline-container", "table", "table-caption", and "table-cell". For all other formatting objects it is set to "false".

5.7 Property Based Transformations

5.7.1 Text-transform Property

The case changes specified by this property are carried out during refinement by changing the value of the "character" property appropriately.

NOTE:

The use of the "text-transform" property is deprecated in XSL due to its severe internationalization issues.

5.8 Unicode BIDI Processing

The characters in certain scripts are written horizontally from right to left. In some documents, in particular those written with the Arabic or Hebrew script, and in some mixed-language contexts, text in a single (visually displayed) block may appear with mixed directionality. This phenomenon is called bidirectionality, or "BIDI" for short.

The Unicode standard [UNICODE] defines a complex algorithm, the Unicode BIDI algorithm [UNICODE UAX #9], for determining the proper directionality of text. The algorithm is based on both an implicit part based on character properties, as well as explicit controls for embeddings and overrides.

The final step of refinement uses this algorithm and the Unicode bidirectional character type of each character to convert the implicit directionality of the text into explicit markup in terms of formatting objects. For example, a sub-sequence of Arabic characters in an otherwise English paragraph would cause the creation of an inline formatting objects with the Arabic characters as its content, with a "direction" property of "rtl" and a "unicode-bidi" property of "bidi-override". The formatting object makes explict the previously implicit right to left positioning of the Arabic characters.

As defined in [UNICODE UAX #9], the Unicode BIDI algorithm takes a stream of text as input, and proceeds in three main phases:

1. Separation of the input text into paragraphs. The rest of the algorithm affects only the text between paragraph separators.

2. Resolution of the embedding levels of the text. In this phase, the bidirectional character types, plus the Unicode directional formatting codes, are used to produce resolved embedding levels. The normative bidirectional character type for each character is specified in the Unicode Character Database [UNICODE Character Database].

3. Reordering the text for display on a line-by-line basis using the resolved embedding levels, once the text has been broken into lines.

The algorithm, as described above, requires some adaptions to fit into the XSL processing model. First, the final, text reordering step is not done during refinement. Instead, the XSL equivalent of re-ordering is done during formatting. The inline-progression-direction of each glyph is used to control the stacking of glyphs as described in [4.2.5 Stacking Constraints]. The inline-progression-direction is determined at the block level by the "writing-mode" property and within the inline formatting objects within a block by the "direction" and "unicode-bidi" properties that were either specified on inline formatting objects generated by tree construction or are are on inline formatting objects introduced by this step of refinement (details below).

Second, the algorithm is applied to a sequence of characters coming from the content of one or more formatting objects. The sequence of characters is created by processing a fragment of the formatting object tree. A fragment is any contiguous sequence of children of some formatting object in the tree. The sequence is created by doing a pre-order traversal of the fragment down to the fo:character level. During the pre-order traversal, every fo:character formatting object adds a character to the sequence. Furthermore, whenever the pre-order scan encounters a node with a "unicode-bidi" property with a value of "embed" or "override", add a Unicode RLO/LRO or RLE/LRE character to the sequence as appropriate to the value of the "direction" and "unicode-bidi" properties. On returning to that node after traversing its content, add a Unicode PDF character. In this way, the formatting object tree fragment is flattened into a sequence of characters. This sequence of characters is called the flattened sequence of characters below.

Third, in XSL the algorithm is applied to delimited text ranges instead of just paragraphs. A delimited text range is a maximal flattened sequence of characters that does not contain any delimiters. Any formatting object that generates block-areas is a delimiter. It acts as a delimiter for its content. It also acts as a delimiter for its parent's content. That is, if the parent has character content, then its children formatting objects that generate block-areas act to break that character content into anonymous blocks each of which is a delimited text range. In a similar manner, the fo:multi-case formatting object acts as delimiter for its content and the content of its parent. Finally, text with an orientation that is not perpendicular to the dominant-baseline acts as a delimiter to text with an orientation perpendicular to the dominant-baseline. We say that text has an orientation perpendicular to the dominant-baseline if the glyphs that correspond to the characters in the text are all oriented perpendicular to the dominant-baseline.

NOTE:

In most cases, a delimited text range is the maximal sequence of characters that would be formatted into a sequence of one or more line-areas. For the fo:multi-case and the text with an orientation perpendicular to the dominant-baseline, the delimited range may be a sub-sequence of a line or sequence of lines. For example, in Japanese formatted in a vertical writing-mode, rotated Latin and Arabic text would be delimited by the vertical Japanese characters that immediately surround the Latin and Arabic text. Any formatting objects that generated inline-areas would have no affect on the determination of the delimited text range.

For each delimited text range, the inline-progression-direction of the nearest ancestor (including self) formatting object that generates a block-area determines the paragraph embedding level used in the Unicode BIDI algorithm. This is the default embedding level for the delimited text range.

Embedding levels are numbers that indicate how deeply the text is nested, and the default direction of text on that level. The minimum embedding level of text is zero, and the maximum embedding level is level 61. Having more than 61 embedding levels is an error. An XSL processor may signal the error. If it does not signal the error, it must recover by allowing a higher maximum number of embedding levels.

The second step of the Unicode BIDI algorithm labels each character in the delimited text range with a resolved embedding level. The resolved embedding level of each character will be greater than or equal to the paragraph embedding level. Right-to-left text will always end up with an odd level, and left-to-right and numeric text will always end up with an even level. In addition, numeric text will always end up with a higher level than the paragraph level.

Once the resolved embedding levels are determined for the delimited text range, new fo:bidi-override formatting objects with appropriate values for the "direction" and "unicode-bidi" properties are inserted into the formatting object tree fragment that was flattened into the delimited text range such that the following constraints are satisfied:

1. For any character in the delimited text range, the inline-progression-direction of the character must match its resolved embedding level.

2. For each resolved embedding level L from the paragraph embedding level to the maximum resolved embedding level, and for each maximal contiguous sequence of characters S for which the resolved embedding level of each character is greater than or equal to L,

   1. There is an inline formatting object F which has as its content the formatting object tree fragment that flattens to S and has a "direction" property consistent with the resolved embedding level L.

      NOTE:

      F need not be an inserted formatting object if the constraint is met by an existing formatting object or by specifying values for the "direction" and "unicode-bidi" properties on an existing formatting object.

   2. All formatting objects that contain any part of the sequence S are properly nested in F and retain the nesting relationships they had in the formatting object tree prior to the insertion of the new formatting objects.

      NOTE:

      Satisfying this constraint may require splitting one or more existing formatting objects in the formatting object tree each into a pair of formatting objects each of which has the same set of computed property values as the original, unsplit formatting object. One of the pair would be ended before the start of F or start after the end of F and the other would start after the start of F or would end before the end of F, respectively. The created pairs must continue to nest properly to satisfy this constraint. For example, assume Left-to-right text is represented by the character "L" and Right-to-left text is represented by "R". In the sub-tree

       <fo:block>
         LL
         <fo:inline ID="A">LLLRRR</fo:inline>
         RR
       </fo:block>
      

      assuming a paragraph embedding level of "0", the resolved embedding levels would require the following (inserted and replicated) structure:

       <fo:block>
         LL
         <fo:inline ID="A">LLL</fo:inline>
         <fo:bidi-override direction="rtl">
           <fo:inline ID="A+">RRR</fo:inline>
           RR
         </fo:bidi-override>
       </fo:block>
      

      Note that the fo:inline with ID equal "A" has been split into two fo:inlines with the first one having the original ID of "A" and the second having an ID of "A+". Since ID's must be unique, the computed value of any ID or Key property must not be replicated in the second member of the pair. The value of "A+" was just used for illustrative purposes.

3. No fewer fo:bidi-override formatting objects can be inserted and still satisfy the above constraints. That is, add to the refined formatting object tree only as many fo:bidi-override formatting objects, beyond the formatting objects created during tree construction, as are needed to represent the embedding levels present in the document.

5.9 Expressions

All property value specifications in attributes within an XSL stylesheet can be expressions. These expressions represent the value of the property specified. The expression is first evaluated and then the resultant value is used to determine the value of the property.

5.9.1 Property Context

Properties are evaluated against a property-specific context. This context provides:

• A list of allowed resultant types for a property value.

• Conversions from resultant expression value types to an allowed type for the property.

• The current font-size value.

• Conversions from relative numerics by type to absolute numerics within additive expressions.

NOTE:

It is not necessary that a conversion is provided for all types. If no conversion is specified, it is an error.

When a type instance (e.g., a string, a keyword, a numeric, etc.) is recognized in the expression it is evaluated against the property context. This provides the ability for specific values to be converted with the property context's specific algorithms or conversions for use in the evaluation of the expression as a whole.

For example, the "auto" enumeration token for certain properties is a calculated value. Such a token would be converted into a specific type instance via an algorithm specified in the property definition. In such a case the resulting value might be an absolute length specifying the width of some aspect of the formatting object.

In addition, this allows certain types like relative numerics to be resolved into absolute numerics prior to mathematical operations.

All property contexts allow conversions as specified in [5.9.12 Expression Value Conversions].

5.9.2 Evaluation Order

When a set of properties is being evaluated for a specific formatting object in the formatting object tree there is a specific order in which properties must be evaluated. Essentially, the "font-size" property must be evaluated first before all other properties. Once the "font-size" property has been evaluated, all other properties may be evaluated in any order.

When the "font-size" property is evaluated, the current font-size for use in evaluation is the font-size of the parent element. Once the "font-size" property has been evaluated, that value is used as the current font-size for all property contexts of all properties value expressions being further evaluated.

5.9.3 Basics

5.9.4 Function Calls

5.9.5 Numerics

A numeric represents all the types of numbers in an XSL expression. Some of these numbers are absolute values. Others are relative to some other set of values. All of these values use a floating-point number to represent the number-part of their definition.

A floating-point number can have any double-precision 64-bit format IEEE 754 value [IEEE 754]. These include a special "Not-a-Number" (NaN) value, positive and negative infinity, and positive and negative zero. See Section 4.2.3 of [JLS] for a summary of the key rules of the IEEE 754 standard.

The following operators may be used with numerics:

+

Performs addition.

-

Performs subtraction or negation.

*

Performs multiplication.

div

Performs floating-point division according to IEEE 754.

mod

Returns the remainder from a truncating division.

NOTE:

Since XML allows - in names, the - operator (when not used as a UnaryExpr negation) typically needs to be preceded by white space. For example the expression 10pt - 2pt means subtract 2 points from 10 points. The expression 10pt-2pt would mean a length value of 10 with a unit of "pt-2pt".

NOTE:

The following are examples of the mod operator:

• 5 mod 2 returns 1

• 5 mod -2 returns 1

• -5 mod 2 returns -1

• -5 mod -2 returns -1

NOTE:

The mod operator is the same as the % operator in Java and ECMAScript and is not the same as the IEEE remainder operation, which returns the remainder from a rounding division.

Numeric Expressions

NOTE:

The effect of this grammar is that the order of precedence is (lowest precedence first):

• +, -

• *, div, mod

and the operators are all left associative. For example, 2*3 + 4 div 5 is equivalent to (2*3) + (4 div 5).

If a non-numeric value is used in an AdditiveExpr and there is no property context conversion from that type into an absolute numeric value, the expression is invalid and considered an error.

5.9.6 Absolute Numerics

An absolute numeric is an absolute length which is a pair consisting of a Number and a UnitName raised to a power. When an absolute length is written without a unit, the unit power is assumed to be zero. Hence, all floating point numbers are a length with a power of zero.

Each unit name has associated with it an internal ratio to some common internal unit of measure (e.g., a meter). When a value is written in a property expression, it is first converted to the internal unit of measure and then mathematical operations are performed.

In addition, only the mod, addition, and subtraction operators require that the numerics on either side of the operation be absolute numerics of the same unit power. For other operations, the unit powers may be different and the result should be mathematically consistent as with the handling of powers in algebra.

A property definition may constrain an absolute length to a particular power. For example, when specifying font-size, the value is expected to be of power "one". That is, it is expected to have a single powered unit specified (e.g., 10pt).

When the final value of a property is calculated, the resulting power of the absolute numeric must be either zero or one. If any other power is specified, the value is an error.

5.9.7 Relative Numerics

Relative lengths are values that are calculated relative to some other set of values. When written as part of an expression, they are either converted via the property context into an absolute numeric or passed verbatim as the property value.

It is an error if the property context has no available conversion for the relative numeric and a conversion is required for expression evaluation (e.g., within an add operation).

5.9.7.1 Percents

Percentages are values that are counted in 1/100 units. That is, 10% as a percentage value is 0.10 as a floating point number. When converting to an absolute numeric, the percentage is defined in the property definition as being a percentage of some known property value. If the percentage evaluates to "auto" the complete expression evaluates to "auto".

For example, a value of "110%" on a "font-size" property would be evaluated to mean 1.1 times the current font size. Such a definition of the allowed conversion for percentages is specified on the property definition. If no conversion is specified, the resulting value is a percentage.

5.9.7.2 Relative Lengths

A relative length is a unit-based value that is measured against the current value of the font-size property.

There is only one relative unit of measure, the "em". The definition of "1em" is equal to the current font size. For example, a value of "1.25em" is 1.25 times the current font size.

When an em measurement is used in an expression, it is converted according to the font-size value of the current property's context. The result of the expression is an absolute length. See [7.8.4 "font-size"].

5.9.8 Strings

Strings are represented either as literals or as an enumeration token. All properties contexts allow conversion from enumeration tokens to strings. See [5.9.12 Expression Value Conversions].

5.9.9 Colors

A color is a set of values used to identify a particular color from a color space. Only RGB [sRGB] (Red, Green, Blue) and ICC (International Color Consortium) [ICC] colors are included in this Recommendation.

RGB colors are directly represented in the expression language using a hexadecimal notation. ICC colors can be accessed through an rgb-icc function. Colors can also be specified through the system-color function or through conversion from an EnumerationToken via the property context.

5.9.10 Keywords

Keywords are special tokens in the grammar that provide access to calculated values or other property values. The allowed keywords are defined in the following subsections.

5.9.10.1 inherit

The property takes the same computed value as the property for the formatting object's parent object.

NOTE:

"inherit" is not allowed as an expression mixed with operations. The same functionality is provided by the from-parent() function, which can be mixed with operations.

5.9.11 Lexical Structure

When processing an expression, white space (ExprWhitespace) may be allowed before or after any expression token even though it is not explicitly defined as such in the grammar. In some cases, white space is necessary to make tokens in the grammar lexically distinct. Essentially, white space should be treated as if it does not exist after tokenization of the expression has occurred.

The following special tokenization rules must be applied in the order specified to disambiguate the grammar:

• If the character following an NCName (possibly after intervening ExprWhitespace) is "(", then the token must be recognized as FunctionName.

• A number terminates at the first occurrence of a non-digit character other than ".". This allows the unit token for length quantities to parse properly.

• When an NCName immediately follows a Number, it should be recognized as a UnitName or it is an error.

• The Keyword values take precedence over EnumerationToken.

• If a NCName follows a numeric, it should be recognized as an OperatorName or it is an error.

Expression Lexical Structure

5.9.12 Expression Value Conversions

Values that are the result of an expression evaluation may be converted into property value types. In some instances this is a simple verification of set membership (e.g., is the value a legal country code). In other cases, the value is expected to be a simple type like an integer and must be converted.

It is not necessary that all types be allowed to be converted. If the expression value cannot be converted to the necessary type for the property value, it is an error.

The following table indicates what conversions are allowed.

The specific conversion to be applied is property specific and can be found in the definition of each property.

NOTE:

Conversions of compound property values are not allowed; thus for example, space-before.optimum="inherited-property-value(space-before)" is invalid. Permitted are, for example, space-before="inherited-property-value(space-before)" and space-before.optimum="inherited-property-value(space-before.optimum)" since they do not require conversion.

5.9.13 Definitions of Units of Measure

The units of measure in this Recommendation have the following definitions:

5.9.13.1 Pixels

XSL interprets a 'px' unit to be a request for the formatter to choose a device-dependent measurement that approximates viewing one pixel on a typical computer monitor. This interpretation is follows:

1. The preferred definition of one 'px' is:

   • The actual distance covered by the largest integer number of device dots (the size of a device dot is measured as the distance between dot centers) that spans a distance less-than-or-equal-to the distance specified by the arc-span rule in http://www.w3.org/TR/REC-CSS2//syndata.html#x39. In XSL this is assumed to be 0.28mm [approximately 1/90"] for print, desktop computer monitors, and hand-held devices viewed at normal viewing distances.

   • A minimum of the size of 1 device dot should be used.

   • This calculation is done separately in each axis, and may have a different value in each axis.

2. However, implementors may instead simply pick a fixed conversion factor, treating 'px' as an absolute unit of measurement (such as 1/92" or 1/72").

NOTE:

Pixels should not be mixed with other absolute units in expressions as they may cause undesirable effects. Also, particular caution should be used with inherited property values that may have been specified using pixels.

If the User Agent chooses a measurement for a 'px' that does not match an integer number of device dots in each axis it may produce undesirable effects, such as:

• moiré patterns in scaled raster graphics

• unrenderable overlapping areas when the renderer rounds fonts or graphics sizes upward to its actual dot-size

• large spaces between areas when the renderer rounds fonts or graphics sizes downward to its actual dot-size

• unreadable results including unacceptably small text/layout (for example, a layout was done at 72 dpi [dots per inch], but the renderer assumed the result was already specified in device dots and renders it at 600 dpi).

Stylesheet authors should understand a pixel's actual size may vary from device to device:

• stylesheets utilizing 'px' units may not produce consistent results across different implementations or different output devices from a single implementation

• even if stylesheets are expressed entirely in 'px' units the results may vary on different devices

5.10 Core Function Library

5.10.1 Number Functions

Function: numeric floor( numeric)

The floor function returns the largest (closest to positive infinity) integer that is not greater than the argument. The numeric argument to this function must be of unit power zero.

NOTE:

If it is necessary to use the floor function for a property where a unit power of one is expected, then an expression such as: "floor(1.4in div 1.0in)*1.0in" must be used. This applies to the ceiling, round, and other such functions where a unit power of zero is required.

Function: numeric ceiling(numeric)

The ceiling function returns the smallest (closest to negative infinity) integer that is not less than the argument. The numeric argument to this function must be of unit power zero.

Function: numeric round(numeric)

The round function returns the integer that is closest to the argument. If there are two such numbers, then the one that is closest to positive infinity is returned. The numeric argument to this function must be of unit power zero.

Function: numeric min( numeric , numeric)

The min function returns the minimum of the two numeric arguments. These arguments must have the same unit power.

Function: numeric max(numeric , numeric)

The max function returns the maximum of the two numeric arguments. These arguments must have the same unit power.

Function: numeric abs( numeric)

The abs function returns the absolute value of the numeric argument. That is, if the numeric argument is negative, it returns the negation of the argument.

5.10.2 Color Functions

Function: color rgb(numeric , numeric , numeric)

The rgb function returns a specific color from the RGB color space. The parameters to this function must be numerics (real numbers) with a length power of zero.

Function: color rgb-icc(numeric , numeric , numeric , NCName , numeric , numeric)

The rgb-icc function returns a specific color from the ICC Color Profile. The color profile is specified by the name parameter (the fourth parameter). This color profile must have been declared in the fo:declarations formatting object using an fo:color-profile formatting object.

The first three parameters specify a fallback color from the sRGB color space. This color is used when the color profile is not available.

The color is specified by a sequence of one or more color values (real numbers) specified after the name parameter. These values are specific to the color profile.

Function: color system-color( NCName)

The system-color function returns a system defined color with a given name.

5.10.3 Font Functions

Function: object system-font( NCName , NCName)

The system-font function returns a characteristic of a system font. The first argument is the name of the system font and the second argument, which is optional, names the property that specifies the characteristic. If the second argument is omitted, then the characteristic returned is the same as the name of the property to which the expression is being assigned.

For example, the expression "system-font(heading,font-size)" returns the font-size characteristic for the system font named "heading". This is equivalent to the property assignment 'font-size="system-font(heading)"'.

5.10.4 Property Value Functions

Function: object inherited-property-value(NCName)

The inherited-property-value function returns the inherited value of the property whose name matches the argument specified, or if omitted for the property for which the expression is being evaluated. It is an error if this property is not an inherited property.

The returned "inherited value" is the computed value of this property on this object's parent. In particular, given the following example:

<fo:list-block>
  ...
  <fo:list-item color="red">
    <fo:list-item-body background-color="green">
      <fo:block background-color="inherited-property-value(color)">
      </fo:block>
    </fo:list-item-body>
  </fo:list-item>
</fo:list-block>

The background-color property on the fo:block is assigned the value "red" because the (computed, after inheritance) value of the color (not background-color) property on the fo:list-item-body that is the parent of fo:block is "red".

Function: numeric label-end()

The label-end function returns the calculated label-end value for lists. See the definition in [7.28.3 "provisional-label-separation"].

Function: numeric body-start()

The body-start function returns the calculated body-start value for lists. See the definition in [7.28.4 "provisional-distance-between-starts"].

NOTE:

When this function is used outside of a list, it still returns a calculated value as specified.

Function: object from-parent( NCName)

The from-parent function returns a computed value of the property whose name matches the argument specified, or if omitted for the property for which the expression is being evaluated. The value returned is that for the parent of the formatting object for which the expression is evaluated. If there is no parent, the value returned is the initial value. If the argument specifies a shorthand property and if the expression only consists of the from-parent function with an argument matching the property being computed, it is interpreted as an expansion of the shorthand with each property into which the shorthand expands, each having a value of from-parent with an argument matching the property. It is an error if arguments matching a shorthand property are used in any other way.

Function: object from-nearest-specified-value( NCName)

The from-nearest-specified-value function returns a computed value of the property whose name matches the argument specified, or if omitted for the property for which the expression is being evaluated. The value returned is that for the closest ancestor of the formatting object for which the expression is evaluated on which there is an assignment of the property in the XML result tree in the fo namespace. If there is no such ancestor, the value returned is the initial value. If the argument specifies a shorthand property and if the expression only consists of the from-nearest-specified-value function with an argument matching the property being computed, it is interpreted as an expansion of the shorthand with each property into which the shorthand expands, each having a value of from-nearest-specified-value with an argument matching the property. It is an error if arguments matching a shorthand property are used in any other way.

Function: object from-table-column( NCName)

The from-table-column function returns the inherited value of the property whose name matches the argument specified, or if omitted for the property for which the expression is being evaluated, from the fo:table-column whose column-number matches the column for which this expression is evaluated and whose number-columns-spanned also matches any span. If there is no match for the number-columns-spanned, it is matched against a span of 1. If there is still no match, the initial value is returned. It is an error to use this function on formatting objects that are not an fo:table-cell or its descendants.

Function: numeric proportional-column-width( numeric)

The proportional-column-width function returns N units of proportional measure where N is the argument given to this function. The column widths are first determined ignoring the proportional measures. The difference between the table-width and the sum of the column widths is the available proportional width. One unit of proportional measure is the available proportional width divided by the sum of the proportional factors. It is an error to use this function on formatting objects other than an fo:table-column. It is also an error to use this function if the fixed table layout is not used.

Function: object merge-property-values( NCName)

The merge-property-values function returns a value of the property whose name matches the argument, or if omitted for the property for which the expression is being evaluated. The value returned is the specified value on the last fo:multi-property-set, of the parent fo:multi-properties, that applies to the User Agent state. If there is no such value, the computed value of the parent fo:multi-properties is returned.

NOTE:

The test for applicability of a User Agent state is specified using the "active-state" property.

It is an error to use this function on formatting objects other than an fo:wrapper that is the child of an fo:multi-properties.

5.11 Property Datatypes

Certain property values are described in terms of compound datatypes, in terms of restrictions on permitted number values, or strings with particular semantics.

The compound datatypes, such as space, are represented in the result tree as multiple attributes. The names of these attributes consist of the property name, followed by a period, followed by the component name. For example a "space-before" property may be specified as:

space-before.minimum="2.0pt"
space-before.optimum="3.0pt"
space-before.maximum="4.0pt"
space-before.precedence="0"
space-before.conditionality="discard"

A short form of compound value specification may be used, in cases where the datatype has some <length> components and for the <keep> datatype. In the first case the specification consists of giving a <length> value to an attribute with a name matching a property name. Such a specification gives that value to each of the <length> components and the initial value to all the non-<length> components. For example:

space-before="4.0pt"

is equivalent to a specification of

space-before.minimum="4.0pt"
space-before.optimum="4.0pt"
space-before.maximum="4.0pt"
space-before.precedence="0"
space-before.conditionality="discard"

NOTE:

Since a <percentage> value, that is not interpreted as "auto", is a valid <length> value it may be used in a short form.

For the <keep> datatype the specification consists of giving a value that is valid for a component to an attribute with a name matching a property name. Such a specification gives that value to each of the components. For example:

keep-together="always"

is equivalent to a specification of

keep-together.within-line="always"
keep-together.within-colums="always"
keep-together.within-page="always"

Short forms may be used together with complete forms; the complete forms have precedence over the expansion of a short form. For example:

space-before="4.0pt"
space-before.maximum="6.0pt"

is equivalent to a specification of

space-before.minimum="4.0pt"
space-before.optimum="4.0pt"
space-before.maximum="6.0pt"
space-before.precedence="0"
space-before.conditionality="discard"

Compound values of properties are inherited as a unit and not as individual components. After inheritance any complete form specification for a component is used to set its value.

The following defines the syntax for specifying the datatypes usable in property values:

<integer>

A signed integer value which consists of an optional '+' or '-' character followed by a sequence of digits. A property may define additional constraints on the value.

NOTE:

A '+' sign is allowed for CSS2 compatibility.

<number>

A signed real number which consists of an optional '+' or '-' character followed by a sequence of digits followed by an optional '.' character and sequence of digits. A property may define additional constraints on the value.

<length>

A signed length value where a 'length' is a real number plus a unit qualification. A property may define additional constraints on the value.

<length-range>

A compound datatype, with components: minimum, optimum, maximum. Each component is a <length>. If "minimum" is greater than optimum, it will be treated as if it had been set to "optimum". If "maximum" is less than optimum, it will be treated as if it had been set to "optimum". A property may define additional constraints on the values.

<length-conditional>

A compound datatype, with components: length, conditionality. The length component is a <length>. The conditionality component is either "discard" or "retain". A property may define additional constraints on the values.

<length-bp-ip-direction>

A compound datatype, with components: block-progression-direction, and inline-progression-direction. Each component is a <length>. A property may define additional constraints on the values.

<space>

A compound datatype, with components: minimum, optimum, maximum, precedence, and conditionality. The minimum, optimum, and maximum components are <length>s. The precedence component is either "force" or an <integer>. The conditionality component is either "discard" or "retain". If "minimum" is greater than optimum, it will be treated as if it had been set to "optimum". If "maximum" is less than optimum, it will be treated as if it had been set to "optimum".

<keep>

A compound datatype, with components: within-line, within-column, and within-page. The value of each component is either "auto", "always", or an <integer>.

<angle>

A representation of an angle consisting of an optional '+' or '-' character immediately followed by a <number> immediately followed by an angle unit identifier. Angle unit identifiers are: 'deg' (for degrees), 'grad' (for grads), and 'rad' (for radians). The specified values are normalized to the range 0deg to 360deg. A property may define additional constraints on the value.

<percentage>

A signed real percentage which consists of an optional '+' or '-' character followed by a sequence of digits followed by an optional '.' character and sequence of digits followed by '%'. A property may define additional constraints on the value.

<character>

A single Unicode character.

<string>

A sequence of characters.

<name>

A string of characters representing a name. It must conform to the definition of an NCName in [XML Names].

<family-name>

A string of characters identifying a font.

<color>

Either a string of characters representing a keyword or a color function defined in [5.10.2 Color Functions]. The list of keyword color names is: aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, purple, red, silver, teal, white, and yellow.

<country>

A string of characters conforming to an ISO 3166 country code.

<language>

A string of characters conforming to the ISO 639 3-letter code.

<script>

A string of characters conforming to an ISO 15924 script code.

<id>

A string of characters conforming to the definition of an NCName in [XML Names] and is unique within the stylesheet.

<idref>

A string of characters conforming to the definition of an NCName in [XML Names] and that matches an ID property value used within the stylesheet.

<uri-specification>

A sequence of characters that is "url(", followed by optional white space, followed by an optional single quote (') or double quote (") character, followed by a URI reference as defined in [RFC2396], followed by an optional single quote (') or double quote (") character, followed by optional white space, followed by ")". The two quote characters must be the same and must both be present or absent. If the URI reference contains a single quote, the two quote characters must be present and be double quotes.

<time>

A <number> immediately followed by a time unit identifier. Time unit identifiers are: 'ms' (for milliseconds) and 's' (for seconds).

<frequency>

A <number> immediately followed by a frequency unit identifier. Frequency unit identifiers are: 'Hz' (for Hertz) and 'kHz' (for kilo Hertz).

6 Formatting Objects

6.1 Introduction to Formatting Objects

The refined formatting object tree describes one or more intended presentations of the information within this tree. Formatting is the process which converts the description into a presentation. See [3 Introduction to Formatting]. The presentation is represented, abstractly, by an area tree, as defined in the area model. See [4 Area Model]. Each possible presentation is represented by one or more area trees in which the information in the refined formatting object tree is positioned on a two and one-half dimensional surface.

There are three kinds of formatting objects: (1) those that generate areas, (2) those that return areas, but do not generate them, and (3) those that are used in the generation of areas. The first and second kinds are typically called flow objects. The third kind is either a layout object or an auxiliary object. The kind of formatting object is indicated by the terminology used with the object. Formatting objects of the first kind are said to "generate one or more areas". Formatting objects of the second kind are said to "return one or more areas". Formatting objects of the first kind may both generate and return areas. Formatting objects of the third kind are "used in the generation of areas"; that is, they act like parameters to the generation process.

6.1.1 Definitions Common to Many Formatting Objects

This categorization leads to defining two traits which characterize the relationship between an area and the formatting objects which generate and return that area. These traits are generated-by and returned-by.

The value of the generated-by trait is a single formatting object. A formatting object F is defined to generate an area A if the semantics of F specify the generation of one or more areas and A is one of the areas thus generated, or is a substituted form of one of the areas thus generated, as specified in section [4.7.2 Line-building].

In the case of substituted glyph-areas, the generating formatting object is deemed to be the formatting object which generated the glyph-area which comes first in the sequence of substituted glyph-areas. In the case of an inserted glyph-area (e.g., an automatically-generated hyphen) the generating formatting object is deemed to be the generating formatting object of the last glyph-area preceding the inserted glyph-area in the pre-order traversal of the area tree.

The value of the returned-by trait is a set of pairs, where each pair consists of a formatting object and a positive integer. The integer represents the position of the area in the ordering of all areas returned by the formatting object.

A formatting object F is defined to return the sequence of areas A, B, C, ... if the pair (F,1) is a member of the returned-by trait of A, the pair (F,2) is a member of the returned-by trait of B, the pair (F,3) is a member of the returned-by trait of C, ...

If an area is a member of the sequence of areas returned by a formatting object, then either it was generated by the formatting object or it was a member of the sequence of areas returned by a child of that formatting object. Not all areas returned by a child of a formatting object need be returned by that formatting object. A formatting object may generate an area that has, as some of its children areas, areas returned by the children of that formatting object. These children (in the area tree) of the generated area are not returned by the formatting object to which they were returned.

A set of nodes in a tree is a lineage if:

• there is a node N in the set such that all the nodes in the set are ancestors of N, and

• for every node N in the set, if the set contains an ancestor of N, it also contains the parent of N.

The set of formatting objects that an area is returned by is a lineage.

Areas returned by a formatting object may be either normal or out-of-line. Normal areas represent areas in the "normal flow of text"; that is, they become area children of the areas generated by the formatting object to which they are returned. Normal areas have a returned-by lineage of size one. There is only one kind of normal area.

Out-of-line areas are areas used outside the normal flow of text either because they are absolutely positioned or they are part of a float or footnote. Out-of-line areas may have a returned-by lineage of size greater than one.

The area-class trait indicates which class, normal or out-of-line, an area belongs to. For out-of-line areas, it also indicates the subclass of out-of-line area. The values for this trait are: "xsl-normal", "xsl-absolute", "xsl-footnote", "xsl-side-float", or "xsl-before-float". An area is normal if and only if the value of the area-class trait is "xsl-normal"; otherwise, the area is an out-of-line area. (See section [4.2.5 Stacking Constraints].)

The areas returned-by a given formatting object are ordered as noted above. This ordering defines an ordering on the sub-sequence of areas that are of a given area-class, such as the sub-sequence of normal areas. An area A precedes an area B in the sub-sequence if and only if area A precedes area B in the areas returned-by the formatting objects.

A reference-area chain is defined as a sequence of reference-areas that is either generated by the same formatting object that is not a page-sequence formatting object, or that consists of the region reference-areas or normal-flow-reference-areas (see [6.4.13 fo:region-body]) generated using region formatting objects assigned to the same flow (see [6.4.1.4 Flows and Flow Mapping]). The reference-areas in the sequence are said to be "contained" by the reference-area chain, and they have the same ordering relative to each other in the sequence as they have in the area tree, using pre-order traversal order of the area tree.

6.2 Formatting Object Content

The content of a formatting object is described using XML content-model syntax. In some cases additional constraints, not expressible in XML content models, are given in prose.

The parameter entity, "%block;" in the content models below, contains the following formatting objects:

     block
     block-container
     table-and-caption
     table
     list-block

The parameter entity, "%inline;" in the content models below, contains the following formatting objects:

     bidi-override
     character
     external-graphic
     instream-foreign-object
     inline
     inline-container
     leader
     page-number
     page-number-citation
     basic-link
     multi-toggle

The following formatting objects are "neutral" containers and may be used, provided that the additional constraints listed under each formatting object are satisfied, anywhere where #PCDATA, %block;, or %inline; are allowed:

     multi-switch
     multi-properties
     wrapper
     retrieve-marker

The following "out-of-line" formatting objects may be used anywhere where #PCDATA, %block;, or %inline; are allowed (except as a descendant of any "out-of-line" formatting object):

     float

The following "out-of-line" formatting objects may be used anywhere where #PCDATA or %inline; are allowed (except as a descendant of any "out-of-line" formatting object):

     footnote

6.3 Formatting Objects Summary

basic-link

The fo:basic-link is used for representing the start resource of a simple link.

bidi-override

The fo:bidi-override inline formatting object is used where it is necessary to override the default Unicode-bidirectional-algorithm direction for different (or nested) inline scripts in mixed-language documents.

block

The fo:block formatting object is commonly used for formatting paragraphs, titles, headlines, figure and table captions, etc.

block-container

The fo:block-container flow object is used to generate a block-level reference-area.

character

The fo:character flow object represents a character that is mapped to a glyph for presentation.

color-profile

Used to declare a color profile for a stylesheet.

conditional-page-master-reference

The fo:conditional-page-master-reference is used to identify a page-master that is to be used when the conditions on its use are satisfied.

declarations

Used to group global declarations for a stylesheet.

external-graphic

The fo:external-graphic flow object is used for a graphic where the graphics data resides outside of the XML result tree in the fo namespace.

float

The fo:float serves two purposes. It can be used so that during the normal placement of content, some related content is formatted into a separate area at beginning of the page (or of some following page) where it is available to be read without immediately intruding on the reader. Alternatively, it can be used when an area is intended to float to one side, with normal content flowing alongside.

flow

The content of the fo:flow formatting object is a sequence of flow objects that provides the flowing text content that is distributed into pages.

footnote

The fo:footnote is used to produce a footnote citation and the corresponding footnote.

footnote-body

The fo:footnote-body is used to generate the content of the footnote.

initial-property-set

The fo:initial-property-set specifies formatting properties for the first line of an fo:block.

inline

The fo:inline formatting object is commonly used for formatting a portion of text with a background or enclosing it in a border.

inline-container

The fo:inline-container flow object is used to generate an inline reference-area.

instream-foreign-object

The fo:instream-foreign-object flow object is used for an inline graphic or other "generic" object where the object data resides as descendants of the fo:instream-foreign-object.

layout-master-set

The fo:layout-master-set is a wrapper around all masters used in the document.

leader

The fo:leader formatting object is used to generate leaders consisting either of a rule or of a row of a repeating character or cyclically repeating pattern of characters that may be used for connecting two text formatting objects.

list-block

The fo:list-block flow object is used to format a list.

list-item

The fo:list-item formatting object contains the label and the body of an item in a list.

list-item-body

The fo:list-item-body formatting object contains the content of the body of a list-item.

list-item-label

The fo:list-item-label formatting object contains the content of the label of a list-item; typically used to either enumerate, identify, or adorn the list-item's body.

marker

The fo:marker is used in conjunction with fo:retrieve-marker to produce running headers or footers.

multi-case

The fo:multi-case is used to contain (within an fo:multi-switch) each alternative sub-tree of formatting objects among which the parent fo:multi-switch will choose one to show and will hide the rest.

multi-properties

The fo:multi-properties is used to switch between two or more property sets that are associated with a given portion of content.

multi-property-set

The fo:multi-property-set is used to specify an alternative set of formatting properties that, dependent on a User Agent state, are applied to the content.

multi-switch

The fo:multi-switch wraps the specification of alternative sub-trees of formatting objects (each sub-tree being within an fo:multi-case), and controls the switching (activated via fo:multi-toggle) from one alternative to another.

multi-toggle

The fo:multi-toggle is used within an fo:multi-case to switch to another fo:multi-case.

page-number

The fo:page-number formatting object is used to represent the current page-number.

page-number-citation

The fo:page-number-citation is used to reference the page-number for the page containing the first normal area returned by the cited formatting object.

page-sequence

The fo:page-sequence formatting object is used to specify how to create a (sub-)sequence of pages within a document; for example, a chapter of a report. The content of these pages comes from flow children of the fo:page-sequence.

page-sequence-master

The fo:page-sequence-master specifies sequences of page-masters that are used when generating a sequence of pages.

region-after

This region defines a viewport that is located on the "after" side of fo:region-body region.

region-before

This region defines a viewport that is located on the "before" side of fo:region-body region.

region-body

This region specifies a viewport/reference pair that is located in the "center" of the fo:simple-page-master.

region-end

This region defines a viewport that is located on the "end" side of fo:region-body region.

region-start

This region defines a viewport that is located on the "start" side of fo:region-body region.

repeatable-page-master-alternatives

An fo:repeatable-page-master-alternatives specifies a sub-sequence consisting of repeated instances of a set of alternative page-masters. The number of repetitions may be bounded or potentially unbounded.

repeatable-page-master-reference

An fo:repeatable-page-master-reference specifies a sub-sequence consisting of repeated instances of a single page-master. The number of repetitions may be bounded or potentially unbounded.

retrieve-marker

The fo:retrieve-marker is used in conjunction with fo:marker to produce running headers or footers.

root

The fo:root node is the top node of an XSL result tree. This tree is composed of formatting objects.

simple-page-master

The fo:simple-page-master is used in the generation of pages and specifies the geometry of the page. The page may be subdivided into up to five regions.

single-page-master-reference

An fo:single-page-master-reference specifies a sub-sequence consisting of a single instance of a single page-master.

static-content

The fo:static-content formatting object holds a sequence or a tree of formatting objects that is to be presented in a single region or repeated in like-named regions on one or more pages in the page-sequence. Its common use is for repeating or running headers and footers.

table

The fo:table flow object is used for formatting the tabular material of a table.

table-and-caption

The fo:table-and-caption flow object is used for formatting a table together with its caption.

table-body

The fo:table-body formatting object is used to contain the content of the table body.

table-caption

The fo:table-caption formatting object is used to contain block-level formatting objects containing the caption for the table only when using the fo:table-and-caption.

table-cell

The fo:table-cell formatting object is used to group content to be placed in a table cell.

table-column

The fo:table-column formatting object specifies characteristics applicable to table cells that have the same column and span.

table-footer

The fo:table-footer formatting object is used to contain the content of the table footer.

table-header

The fo:table-header formatting object is used to contain the content of the table header.

table-row

The fo:table-row formatting object is used to group table-cells into rows.

title

The fo:title formatting object is used to associate a title with a given page-sequence. This title may be used by an interactive User Agent to identify the pages. For example, the content of the fo:title can be formatted and displayed in a "title" window or in a "tool tip".

wrapper

The fo:wrapper formatting object is used to specify inherited properties for a group of formatting objects. It has no additional formatting semantics.

6.4 Declarations and Pagination and Layout Formatting Objects

6.4.1 Introduction

The root node of the formatting object tree must be an fo:root formatting object. The children of the fo:root formatting object are a single fo:layout-master-set, an optional fo:declarations, and a sequence of one or more fo:page-sequences. The fo:layout-master-set defines the geometry and sequencing of the pages; the children of the fo:page-sequences, which are called flows (contained in fo:flow and fo:static-content), provide the content that is distributed into the pages. The fo:declarations object is a wrapper for formatting objects whose content is to be used as a resource to the formatting process. The process of generating the pages is done automatically by the XSL processor formatting the result tree.

The children of the fo:layout-master-set are the pagination and layout specifications. The names of these specifications end in "-master". There are two types of pagination and layout specifications: page-masters and page-sequence-masters. Page-masters have the role of describing the intended subdivisions of a page and the geometry of these subdivisions. Page-sequence-masters have the role of describing the sequence of page-masters that will be used to generate pages during the formatting of an fo:page-sequence.

6.4.1.1 Page-sequence-masters

Each fo:page-sequence-master characterizes a set of possible sequences of page-masters. For any given fo:page-sequence, only one of the possible set of sequences will be used. The sequence that is used is any sequence that satisfies the constraints determined by the individual page-masters, the flows which generate pages from the page-masters, and the fo:page-sequence-master itself.

The fo:page-sequence-master is used to determine which page-masters are used and in which order. The children of the fo:page-sequence-master are a sequence of sub-sequence specifications. The page-masters in a sub-sequence may be specified by a reference to a single page-master or as a repetition of one or more page-masters. For example, a sequence might begin with several explicit page-masters and continue with a repetition of some other page-master (or masters).

The fo:single-page-master-reference is used to specify a sub-sequence consisting of a single page-master.

There are two ways to specify a sub-sequence that is a repetition. The fo:repeatable-page-master-reference specifies a repetition of a single page-master. The fo:repeatable-page-master-alternatives specifies the repetition of a set of page-masters. Which of the alternative page-masters is used at a given point in the sub-sequence is conditional and may depend on whether the page number is odd or even, is the first page, is the last page, or is blank. The "maximum-repeats" property on the repetition specification controls the number of repetitions. If this property is not specified, there is no limit on the number of repetitions.

6.4.1.2 Page-masters

A page-master is a master that is used to generate a page. A page is a viewport/reference pair in which the viewport-area is a child of the area tree root. A page-viewport-area is defined to be the viewport-area of a page, and a page-area is defined to be the unique child of a page-viewport-area.

The page-viewport-area is defined by the output medium; the page-area holds the page contents and has the effect of positioning the page contents on the output medium.

A single page-master may be used multiple times. Each time it is used it generates a single page; for example, a page-master that is referenced from an fo:repeatable-page-master-reference will be used by the fo:page-sequence to generate one page for each occurrence of the reference in the specified sub-sequence.

NOTE:

When pages are used with a User Agent such as a Web browser, it is common that the each document has only one page. The viewport used to view the page determines the size of the page. When pages are placed on non-interactive media, such as sheets of paper, pages correspond to one or more of the surfaces of the paper. The size of the paper determines the size of the page.

In this specification, there is only one kind of page-master, the fo:simple-page-master. Future versions of this specification may add additional kinds of page-masters.

An fo:simple-page-master has, as children, specifications for one or more regions.

A region specification is used as a master, the region-master, in generating viewport/reference pair consisting of a region-viewport-area and a region-reference-area. The region-viewport-area is always a child of a page-area generated using the parent of the region-master.

NOTE:

The regions on the page are analogous to "frames" in an HTML document. Typically, at least one of these regions is of indefinite length in one of its dimensions. For languages with a lr-tb (or rl-tb) writing-mode, this region is typically of indefinite length in the top-to-bottom direction. The viewport represents the visible part of the frame. The flow assigned to the region is viewed by scrolling the region reference-area through the viewport.

Each region is defined by a region formatting object. Each region formatting object has a name and a definite position. In addition, the region's height or width is fixed and the other dimension may be either fixed or indefinite. For example, a region that is the body of a Web page may have indefinite height.

The specification of the region determines the size and position of region-viewport-areas generated using the region formatting object. The positioning of the viewport is relative to its page-area parent.

For version 1.0 of this Recommendation, a page-master will consist of up to five regions: "region-body" and four other regions, one on each side of the body. To allow the side regions to correspond to the current writing-mode, these regions are named "region-before" (which corresponds to "header" in the "lr-tb" writing-mode), "region-after" (which corresponds to "footer" in the "lr-tb" writing-mode), "region-start" (which corresponds to a "left-sidebar" in the "lr-tb" writing-mode) and "region-end" (which corresponds to a "right-sidebar" in the "lr-tb" writing-mode). It is expected that a future version of the Recommendation will introduce a mechanism that allows a page-master to contain an arbitrary number of arbitrarily sized and positioned regions.

Some types of region have conditional sub-regions associated with them, and the associated region-reference-areas are divided up by having child areas corresponding to the sub-regions, including a "main-reference-area" for the region. For region-masters to which the column-count property applies, the main-reference-area is further subdivided by having child-areas designated as "span-reference-areas" whose number depends upon the number of spans (i.e. block-areas with span="all") occurring on the page. These in turn are subdivided by having child-areas designated as "normal-flow-reference-areas", whose number depends on the number of columns specified.

6.4.1.3 Page Generation

Pages are generated by the formatter's processing of fo:page-sequences. As noted above, each page is a viewport/reference pair in which the viewport-area is a child of the area tree root. Each page is generated using a page-master to define the region-viewport-areas and region-reference-areas that correspond to the regions specified by that page-master.

Each fo:page-sequence references either an fo:page-sequence-master or a page-master. If the reference is to a page-master, this is interpreted as if it were a reference to an fo:page-sequence-master that repeats the referenced page-master an unbounded number of times. An fo:page-sequence references a page-master if either the fo:page-sequence directly references the page-master via the "master-reference" property or that property references an fo:page-sequence-master that references the page-master.

6.4.1.4 Flows and Flow Mapping

There are two kinds of flows: fo:static-content and fo:flow. An fo:static-content flow holds content, such as the text that goes into headers and footers, that is repeated on many of the pages. The fo:flow flow holds content that is distributed across a sequence of pages. The processing of the fo:flow flow is what determines how many pages are generated to hold the fo:page-sequence. The fo:page-sequence-master is used as the generator of the sequence of page-masters into which the flow children content is distributed.

The children of a flow are a sequence of block-level flow objects. Each flow has a name that is given by its "flow-name" property. No two flows may have the same name.

The assignment of flows to regions on a page-master is determined by a flow-map. The flow-map is an association between the flow children of the fo:page-sequence and regions defined within the page-masters referenced by that fo:page-sequence.

In version 1.0 of this Recommendation, the flow-map is implicit. The "flow-name" property of a flow specifies to which region that flow is assigned. Each region has a "region-name" property. The implicit flow-map assigns a flow to the region that has the same name. In future versions of XSL, the flow-map is expected to become an explicit formatting object.

To avoid requiring users to generate region-names, the regions all have default values for the "region-name" property. The region-body, region-before, region-after, region-start, and region-end have the default names "xsl-region-body", "xsl-region-before", "xsl-region-after", "xsl-region-start", and "xsl-region-end", respectively.

In addition, an fo:static-content formatting object may have a "flow-name" property value of "xsl-before-float-separator" or "xsl-footnote-separator". If a conditional sub-region of the region-body is used to generate a reference-area on a particular page, the fo:static-content whose name corresponds to the conditional sub-region shall be formatted into the reference-area associated with the sub-region, as specified in section [6.10.1.3 Conditional Sub-Regions].

6.4.1.5 Constraints on Page Generation

The areas that are descendants of a page-area are constrained by the page-master used to generate the page-area and the flows that are assigned to the regions specified on the page-master. For fo:flow flows, the areas generated by the descendants of the flow are distributed across the pages in the sequence that were generated using page-masters having the region to which the flow is assigned. For fo:static-content flows, the processing of the flow is repeated for each page generated using a page-master having the region to which the flow is assigned with two exceptions: for a fo:static-content with a flow-name of xsl-before-float-separator, the processing is repeated only for those page-reference-areas which have descendant areas with an area-class of xsl-before-float, and for a fo:static-content with a flow-name of xsl-footnote-separator, the processing is repeated only for those page-reference-areas which have descendant areas with an area-class of xsl-footnote.

6.4.1.6 Pagination Tree Structure

The result tree structure is shown below.

6.4.2 fo:root

Common Usage:

This is the top node of the formatting object tree. It holds an fo:layout-master-set formatting object (which holds all masters used in the document), an optional fo:declarations, and one or more fo:page-sequence objects. Each fo:page-sequence represents a sequence of pages that result from formatting the content children of the fo:page-sequence.

NOTE:

A document can contain multiple fo:page-sequences. For example, each chapter of a document could be a separate fo:page-sequence; this would allow chapter-specific content, such as the chapter title, to be placed within a header or footer.

Areas:

Page-viewport-areas are returned by the fo:page-sequence children of the fo:root formatting object. The fo:root does not generate any areas.

Constraints:

The children of the root of the area tree consist solely of, and totally of, the page-viewport-areas returned by the fo:page-sequence children of the fo:root. The set of all areas returned by the fo:page-sequence children is properly ordered. (See Section [4.7.1 General Ordering Constraints].)

Contents:

(layout-master-set,declarations?,page-sequence+)

The following properties apply to this formatting object:

• [7.25.11 "media-usage"]

6.4.3 fo:declarations

Common Usage:

The fo:declarations formatting object is used to group global declarations for a stylesheet.

Areas:

The fo:declarations formatting object does not generate or return any areas.

Constraints:

None.

Contents:

(color-profile)+

The fo:declarations flow object may have additional child elements in a non-XSL namespace. Their presence does not, however, change the semantics of the XSL namespace objects and properties. The permitted structure of these non-XSL namespace elements is defined for their namespace(s).

6.4.4 fo:color-profile

Common Usage:

The fo:color-profile formatting object is used to declare an ICC Color Profile for a stylesheet. The color-profile is referenced again via the name specified in the "color-profile-name" property.

The color-profile is identified by the URI specified in the "src" property value. This URI may identify an internally recognized color-profile or it may point to a ICC Color Profile encoding that should be loaded and interpreted.

When the color-profile is referenced (e.g., via the rgb-icc function [5.10.2 Color Functions]), the following rules are used:

1. If the color-profile is available, the color value identified from the color-profile should be used.

2. If the color-profile is not available, the sRGB ([sRGB]) fallback must be used.

Areas:

The fo:color-profile formatting object does not generate or return any areas.

Constraints:

None.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.28.7 "src"]
• [7.17.2 "color-profile-name"]
• [7.17.3 "rendering-intent"]

6.4.5 fo:page-sequence

Common Usage:

The fo:page-sequence formatting object is used to specify how to create a (sub-)sequence of pages within a document; for example, a chapter of a report. The content of these pages comes from flow children (consisting of the single fo:flow and any fo:static-content flow objects) of the fo:page-sequence. The layout of these pages comes from the fo:page-sequence-master or page-master referenced by the master-reference trait on the fo:page-sequence. The sequence of areas returned by each of the flow-object children of the fo:page-sequence are made descendants of the generated pages as described below.

Areas:

The fo:page-sequence formatting object generates a sequence of viewport/reference pairs, and returns the page-viewport-areas. For each page-reference-area, and each region specified in the page-master used to generate that page-reference-area, the fo:page-sequence object also generates the viewport/reference pair for the occurrence of that region in that page-reference-area, and may generate a before-float-reference-area, footnote-reference-area, and main-reference-area, and one or more normal-sequence-reference-areas. The generation of these further areas is described in the descriptions of the fo:simple-page-master and region-masters. It may also generate a title-area.

All areas generated by an fo:page-sequence have area-class "xsl-absolute".

Constraints:

Each page-viewport-area/page-reference-area pair is generated using a page-master that satisfies the constraints of the page-sequence-master identified by the master-reference trait of the fo:page-sequence or a page-master that was directly identified by the master-reference trait. The region-viewport-area children of such a page-reference-area must correspond to the regions that are children of that page-master.

The areas generated by the fo:page-sequence have as their descendants the areas returned by the flows that are children of the fo:page-sequence.

The areas returned to the fo:page-sequence by a flow must satisfy four types of constraints:

• Completeness. All areas returned by formatting object descendants of the flow children of the fo:page-sequence become descendants of areas generated by the fo:page-sequence, with the exception of glyph-areas subject to deletion or substitution as in Sections [4.7.2 Line-building] and [4.7.3 Inline-building].

• Flow-map association. All areas returned by flow children of the fo:page-sequence become descendants of region-reference-areas generated from column-areas associated to the flow by the flow-map in effect, except for areas returned from a fo:static-content with a flow-name of xsl-before-float-separator or xsl-footnote-separator.

  Areas returned from an fo:static-content with a flow-name of xsl-before-float-separator become children of the before-float-reference-area of an area associated to an fo:region-body, following all sibling areas of area-class xsl-before-float. Areas returned from an fo:static-content with a flow-name of xsl-footnote-separator become children of the footnote-reference-area of an area associated to an fo:region-body, preceding all sibling areas of area-class xsl-footnote.

• Area-class association. Areas returned by flow children of an fo:page-sequence are distributed as follows: all areas of area-class xsl-footnote must be descendants of a footnote-reference-area; areas of area-class xsl-before-float must be descendants of a before-float-reference-area; all other areas (including normal areas) must be descendants of a main-reference-area for a region.

• Stacking. The stackable areas of a given class returned by children of each flow are properly stacked within the appropriate reference-area, as described above.

If a title-area is generated the following constraints must be satisfied:

• Completeness. All areas returned by formatting object descendants of the fo:title child of the fo:page-sequence become descendants of the title-area generated by the fo:page-sequence, with the exception of glyph-areas subject to deletion or substitution as in Sections [4.7.2 Line-building] and [4.7.3 Inline-building].

• Stacking. The areas returned by children of the fo:title are properly stacked within the title-area.

The default ordering constraint of section [4.7.1 General Ordering Constraints] does not apply to the fo:page-sequence. The default ordering constraints apply to the flow object children inside the single fo:flow; special ordering constraints apply to the child fo:static-content objects.

Contents:

(title?,static-content*,flow)

The following properties apply to this formatting object:

• [7.9.1 "country"]
• [7.24.1 "format"]
• [7.9.2 "language"]
• [7.24.4 "letter-value"]
• [7.24.2 "grouping-separator"]
• [7.24.3 "grouping-size"]
• [7.28.2 "id"]
• [7.25.7 "initial-page-number"]
• [7.25.6 "force-page-count"]
• [7.25.9 "master-reference"]

6.4.6 fo:layout-master-set

Common Usage:

The fo:layout-master-set is a wrapper around all masters used in the document. This includes page-sequence-masters, page-masters, and region-masters.

Areas:

The fo:layout-master-set formatting object generates no area directly. The masters that are the children of the fo:layout-master-set are used by the fo:page-sequence to generate pages.

Constraints:

The value of the master-name trait on each child of the fo:layout-master-set must be unique within the set.

Contents:

(simple-page-master|page-sequence-master)+

6.4.7 fo:page-sequence-master

Common Usage:

The fo:page-sequence-master is used to specify the constraints on and the order in which a given set of page-masters will be used in generating a sequence of pages. Pages are automatically generated when the fo:page-sequence-master is used in formatting an fo:page-sequence.

NOTE:

There are several ways of specifying a potential sequence of pages. One can specify a sequence of references to particular page-masters. This yields a bounded sequence of potential pages. Alternatively, one can specify a repeating sub-sequence of one or more page-masters. This sub-sequence can be bounded or unbounded. Finally one can intermix the two kinds of sub-sequence-specifiers.

Areas:

The fo:page-sequence-master formatting object generates no area directly. It is used by the fo:page-sequence formatting object to generate pages.

Constraints:

The children of the fo:page-sequence-master are a sequence of sub-sequence-specifiers. A page-sequence satisfies the constraint determined by an fo:page-sequence-master if (a) it can be partitioned into a sequence of sub-sequences of pages that map one-to-one to an initial sub-sequence of the sequence of sub-sequence-specifiers that are the children of the fo:page-sequence-master and, (b) for each sub-sequence of pages in the partition, that sub-sequence satisfies the constraints of the corresponding sub-sequence-specifier. The sequence of sub-sequences of pages can be shorter than the sequence of sub-sequence-specifiers.

It is an error if the entire sequence of sub-sequence-specifiers children is exhausted while some areas returned by an fo:flow are not placed. Implementations may recover, if possible, by re-using the sub-sequence-specifier that was last used to generate a page.

Contents:

(single-page-master-reference|repeatable-page-master-reference|repeatable-page-master-alternatives)+

The following properties apply to this formatting object:

• [7.25.8 "master-name"]

6.4.8 fo:single-page-master-reference

Common Usage:

An fo:single-page-master-reference is the simplest sub-sequence-specifier. It specifies a sub-sequence consisting of a single instance of a single page-master. It is used to specify the use of a particular page-master at a given point in the sequence of pages that would be generated using the fo:page-sequence-master that is the parent of the fo:single-page-master-reference.

Areas:

The fo:single-page-master-reference formatting object generates no area directly. It is used by the fo:page-sequence formatting object to generate pages.

Constraints:

The fo:single-page-master-reference has a reference to the fo:simple-page-master which has the same master-name as the master-reference trait on the fo:single-page-master-reference.

The sub-sequence of pages mapped to this sub-sequence-specifier satisfies the constraints of this sub-sequence-specifier if (a) the sub-sequence of pages consists of a single page and (b) that page is constrained to have been generated using the fo:simple-page-master referenced by the fo:single-page-master-reference.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.25.9 "master-reference"]

6.4.9 fo:repeatable-page-master-reference

Common Usage:

An fo:repeatable-page-master-reference is the next simplest sub-sequence-specifier. It specifies a sub-sequence consisting of repeated instances of a single page-master. The number of repetitions may be bounded or potentially unbounded.

Areas:

The fo:repeatable-page-master-reference formatting object generates no area directly. It is used by the fo:page-sequence formatting object to generate pages.

Constraints:

The fo:repeatable-page-master-reference has a reference to the fo:simple-page-master which has the same master-name as the master-reference trait on the fo:repeatable-page-master-reference.

The sub-sequence of pages mapped to this sub-sequence-specifier satisfies the constraints of this sub-sequence-specifier if (a) the sub-sequence of pages consists of zero or more pages, (b) each page is generated using the fo:simple-page-master referenced by the fo:repeatable-page-master-reference, and (c) length of the sub-sequence is less than or equal to the value of maximum-repeats.

If no region-master child of the fo:repeatable-page-master has a region-name associated to any flow in an fo:page-sequence, then the sub-sequence is constrained to have length zero.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.25.9 "master-reference"]
• [7.25.10 "maximum-repeats"]

6.4.10 fo:repeatable-page-master-alternatives

Common Usage:

The fo:repeatable-page-master-alternatives formatting object is the most complex sub-sequence-specifier. It specifies a sub-sequence consisting of repeated instances of a set of alternative page-masters. The number of repetitions may be bounded or potentially unbounded. Which of the alternative page-masters is used at any point in the sequence depends on the evaluation of a condition on the use of the alternative. Typical conditions include, testing whether the page which is generated using the alternative is the first or last page in a page-sequence or is the page blank. The full set of conditions allows different page-masters to be used for the first page, for odd and even pages, for blank pages.

NOTE:

Because the conditions are tested in order from the beginning of the sequence of children, the last alternative in the sequence usually has a condition that is always true and this alternative references the page-master that is used for all pages that do not receive some specialized layout.

Areas:

The fo:repeatable-page-master-alternatives formatting object generates no area directly. This formatting object is used by the fo:page-sequence formatting object to generate pages.

Constraints:

The children of the fo:repeatable-page-master-alternatives are fo:conditional-page-master-references. These children will be called alternatives.

The sub-sequence of pages mapped to this sub-sequence-specifier satisfies the constraints of this sub-sequence-specifier if (a) the sub-sequence of pages consists of zero or more pages, (b) each page is generated using the fo:simple-page-master referenced by the one of the alternatives that are the children of the fo:repeatable-page-master-alternatives, (c) the conditions on that alternative are true, (d) that alternative is the first alternative in the sequence of children for which all the conditions are true, and (e) the length of the sub-sequence is less than or equal to the value of maximum-repeats.

Contents:

(conditional-page-master-reference+)

The following properties apply to this formatting object:

• [7.25.10 "maximum-repeats"]

6.4.11 fo:conditional-page-master-reference

Common Usage:

The fo:conditional-page-master-reference is used to identify a page-master that is to be used when the conditions on its use are satisfied. This allows different page-masters to be used, for example, for even and odd pages, for the first page in a page-sequence, or for blank pages. This usage is typical in chapters of a book or report where the first page has a different layout than the rest of the chapter and the headings and footings on even and odd pages may be different as well.

Areas:

The fo:conditional-page-master-reference formatting object generates no area directly. It is used by the fo:page-sequence formatting object to generate pages.

Constraints:

The fo:conditional-page-master-reference has a reference to the fo:simple-page-master which has the same master-name as the master-reference trait on the fo:conditional-page-master-reference.

There are three traits, page-position, odd-or-even, and blank-or-not-blank that specify the sub-conditions on the use of the referenced page-master. All three sub-conditions must be true for the condition on the fo:conditional-page-master-reference to be true. Since the properties from which these traits are derived are not inherited and the initial value of all the properties makes the corresponding sub-condition true, this really means that the subset of traits that are derived from properties with specified values must make the corresponding sub-condition true.

The sub-condition corresponding to the page-position trait is true if the page generated using the fo:conditional-page-master-reference has the specified position in the sequence of pages generated by the referencing page-sequence; namely, "first", "last", "rest" (not first nor last) or "any" (all of the previous). The referencing page-sequence is the fo:page-sequence that referenced the fo:page-sequence-master from which this fo:conditional-page-master-reference is a descendant.

The sub-condition corresponding to the odd-or-even trait is true if the value of the odd-or-even trait is "any" or if the value matches the parity of the page number of the page generated using the fo:conditional-page-master-reference.

The sub-condition corresponding to the blank-or-not-blank trait is true, if (1) the value of the trait is "not-blank" and the page generated using the fo:conditional-page-master-reference has areas generated by descendants of the fo:flow formatting object; if (2) the value of the trait is "blank" and the page generated using the fo:conditional-page-master-reference is such that there are no areas from the fo:flow to be put on that page (e.g., (a) to maintain proper page parity due to (i) a break-after or break-before value of "even-page" or "odd-page" or (ii) at the start or end of the page-sequence or (b) because the constraints on the areas generated by descendants of the fo:flow formatting object would not be satisfied if they were descendant from this page); or if (3) the value of the trait is "any".

NOTE:

If any page-master referenced from a conditional-page-master-reference with blank-or-not-blank="true" provides a region in which to put fo:flow content, no content is put in that region.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.25.9 "master-reference"]
• [7.25.14 "page-position"]
• [7.25.12 "odd-or-even"]
• [7.25.1 "blank-or-not-blank"]

6.4.12 fo:simple-page-master

Common Usage:

The fo:simple-page-master is used in the generation of pages and specifies the geometry of the page. The page may be subdivided into up to five regions: region-body, region-before, region-after, region-start, and region-end.

NOTE:

For example, if the writing-mode of the fo:simple-page-master is "lr-tb", then these regions correspond to the body of a document, the header, the footer, the left sidebar, and the right sidebar.

NOTE:

The simple-page-master is intended for systems that wish to provide a simple page layout facility. Future versions of this Recommendation will support more complex page layouts constructed using the fo:page-master formatting object.

Areas:

The fo:simple-page-master formatting object generates no area directly. It is used in the generation of pages by an fo:page-sequence.

When the fo:simple-page-master is used to generate a page, a viewport/reference pair is generated, consisting of a page-viewport-area and a page-reference-area. The page-viewport-area represents the physical bounds of the output medium. The page-reference-area represents the portion of the page on which content is intended to appear; that is, the area inside the page margins.

In addition, when the fo:simple-page-master is used to generate a page, viewport/reference pairs that correspond to the regions that are the children of the fo:simple-page-master are also generated. (See the formatting object specifications for the five regions ([6.4.13 fo:region-body], [6.4.14 fo:region-before], [6.4.15 fo:region-after], [6.4.16 fo:region-start], and [6.4.17 fo:region-end]) for the details on the generation of these areas.)

Trait Derivation:

In version 1.0 of this Recommendation, borders and padding are not allowed with a page-reference-area. The remaining traits on the page-reference-area are set according to normal rules for determining the values of traits.

Constraints:

When a page-master is used in the generation of a page, the block-progression-dimension and inline-progression-dimension of the content-rectangle of the page-viewport-area are determined using the computed values of the "page-height" and "page-width" properties.

The traits derived from the margin properties determine the size and position of the content-rectangle of the page-viewport-area. The traits derived from the "margin-top", "margin-bottom", "margin-left" and "margin-right" properties are used to indent the page-reference-area content-rectangle from the corresponding edge of the content-rectangle of the page-viewport-area. Here "top", "bottom", "left" and "right" are determined by the computed values of the "page-height" and "page-width" properties. For sheet media, these values determine the orientation of the sheet; "page-height" is measured from "top" to "bottom". For display media, the display window is always upright; the top of the display screen is "top".

NOTE:

The reference points for the page-viewport-area content-rectangle are in terms of the "top", "bottom", "left", and "right" rather than "before-edge", "after-edge", "start-edge", and "end-edge" because users see the media relative to its orientation and not relative to the writing-mode currently in use.

The value of the page-number trait on the first page returned by the fo:page-sequence is constrained to equal the value of the initial-page-number trait. The value of the page-number trait on subsequent pages is constrained to be one greater than the value on the immediately preceding page.

The format, letter-value, grouping-separator, grouping-size, country, and language traits are used to format the number into a string form, as specified in XSLT, section 7.7.1. This formatted number is used as the value of the fo:page-number flow object.

Constraints applicable to regions:

There are a number of constraints that apply to all the regions that are specified within a given fo:simple-page-master.

If the block-progression-dimension of the properly stacked region-reference-area is greater than the block-progression-dimension of the region-viewport-area that is its parent, then the constraints on the relationship between the region-viewport-area and the region-reference-area depend on values of the overflow trait on the region-master and the kind of flow assigned to the region.

If the flow assigned to the corresponding region is an fo:static-content flow object, then there is no constraint on the block-progression-dimension of the region-reference-area.

If the flow assigned to the corresponding region is an fo:flow formatting object, then

• If the value of the media-usage trait is paginate, or the value of the overflow trait is visible, hidden, or error-if-overflow, then the block-progression-dimension of the region-reference-area is constrained to be no greater than the block-progression-dimension of the region-viewport-area.

• If the value of the media-usage trait is bounded-in-one-dimension or unbounded, and the value of the overflow trait is scroll or auto, then there is no constraint on the block-progression-dimension of the region-reference-area.

Contents:

(region-body,region-before?,region-after?,region-start?,region-end?)

The following properties apply to this formatting object:

• [7.10 Common Margin Properties-Block]
• [7.25.8 "master-name"]
• [7.25.13 "page-height"]
• [7.25.15 "page-width"]
• [7.20.3 "reference-orientation"]
• [7.27.7 "writing-mode"]

6.4.13 fo:region-body

Common Usage:

Used in constructing a simple-page-master. This region specifies a viewport/reference pair that is located in the "center" of the fo:simple-page-master. The overflow trait controls how much of the underlying region-reference-area is visible; that is, whether the region-reference-area is clipped by its parent region-viewport-area.

NOTE:

Typically, for paged media, the areas returned by the fo:flow formatting object in a fo:page-sequence are made to be descendants of a sequence of region-reference-areas that correspond to the region-body. These region-reference-areas are all area descendants of page-areas for which the page-master included an fo:region-body. If the fo:flow flow is assigned to some other region, then the areas returned by the fo:flow are constrained to be descendants of region-reference-areas generated using the assigned region-master.

NOTE:

The body region should be sized and positioned within the fo:simple-page-master so that there is room for the areas returned by the flow that is assigned to the fo:region-body and for any desired side regions, that is, fo:region-before, fo:region-after, fo:region-start and fo:region-end's that are to be placed on the same page. These side regions are positioned within the content-rectangle of the page-reference-area. The margins on the fo:region-body are used to position the region-viewport-area for the fo:region-body and to leave space for the other regions that surround the fo:region-body.

The spacing between the last four regions and the fo:region-body is determined by subtracting the relevant extent trait on the side regions from the trait that corresponds to the "margin-x" property on the fo:region-body.

The fo:region-body may be also be used to provide multiple columns. When the column-count trait is greater than one, then the region-body will be subdivided into multiple columns.

Areas:

The fo:region-body formatting object is used to generate one region-viewport-area and one region-reference-area whenever an fo:simple-page-master that has an fo:region-body as a child is used to generate a page. A scrolling mechanism shall be provided, in an implementation-defined manner, if the value of the overflow trait is "scroll".

The position and size of the region-viewport-area is specified relative to the content-rectangle of the page-reference-area generated by fo:simple-page-master. The content-rectangle of the region-viewport-area is indented from the content-rectangle of the page-reference-area by the values of the "margin-top", "margin-bottom", "margin-left" and "margin-right" properties. In version 1.0 of this Recommendation, the values of the padding and border-width traits must be "0".

The region-reference-area generated using an fo:region-body is the child of the region-viewport-area. The reference-orientation trait of the fo:region-body is used to orient the coordinate system of the region-reference-area generated by the fo:region-body relative to the coordinate system of the page-reference-area generated by fo:simple-page-master (and, therefore, relative to the viewport positioned in that latter coordinate system).

In addition to the viewport/reference pair, when the region-body is used to generate areas, at least one and up to three additional reference-areas are generated. These reference-areas are the optional before-float-reference-area, the optional footnote-reference-area, and the main-reference-area. The latter reference-area comprises the space left after space is borrowed for the other two reference-areas. The main-reference-area has no padding, border, or space associated with it.

NOTE:

If there is no before-float-reference-area or footnote-reference-area child of the region-reference-area, then the content-rectangle of the main-reference-area is coterminous with the content-rectangle of the region-reference-area.

The main-reference-area has as its children a sequence of span-reference-areas. These are reference-area block-areas with zero border and padding, whose inline-progression-dimension is equal to that of the main-reference-area, and which are normally stacked within the main-reference-area.

Each span-reference-area has one or more reference-area children, designated as normal-flow-reference-areas. The number and placement of the children of a span-reference-area depends on the column-count trait of the span-reference-area. In turn, the formatter must generate precisely enough of these span-reference-areas, and so set their column-count traits, that block-areas returned from the fo:flow with a span of "all" are children of span-reference-areas with column-count equal to 1, and block-areas returned from the fo:flow with a span of "none" are children of span-reference-areas with column-count equal to the refined value of the column-count property of the associated region-reference-area.

For each span-reference-area, the number N of normal-flow-reference-area children is equal to the value of the column-count trait.

It is an error to specify a column-count other than 1 if the "overflow" property has the value "scroll". An implementation may recover by behaving as if "1" had been specified.

The inline-progression-dimension of each of these normal-flow-reference-areas is determined by subtracting (N-1) times the column-gap trait from the inline-progression-dimension of the main-reference-area and dividing that result by N. Using "body-in-size" for the name of the inline-progression-dimension of the span-reference-area and "column-in-size" for the name of the size of the normal-flow-reference-areas in the inline-progression-direction, the formula is:

column-in-size = (body-in-size - (N - 1)*column-gap)/N

The block-progression-dimension of the normal-flow-reference-areas is the same as that of the parent span-reference-area.

NOTE:

As noted above, the block-progression-dimension of the span-reference-area may be less than the size of the region-reference-area if a before-float-reference-area or footnote-reference-area are present, or if there is more than one span-reference-area child of the main-reference-area.

The normal-flow-reference-areas are positioned within the span-reference-area as follows: The first column is positioned with the before-edge and start-edge of its content-rectangle coincident with the before-edge and start-edge of the content-rectangle of the span-reference-area. The content-rectangle of the Jth normal-flow-reference-area child of the span-reference-area is positioned with its before-edge coincident with the before-edge of the content-rectangle of the span-reference-area and with is start-edge at ((J-1)*(column-in-size + column-gap)) in the inline-progression-direction. This results in the end-edge of the content-rectangle of the Nth normal-flow-reference-area being coincident with the end-edge of the content-rectangle of the span-reference-area.

NOTE:

If the writing-mode is "rl-tb", the above description means that the columns are ordered from right-to-left as would be expected. This follows because the start-edge is on the right in an "rl-tb" writing-mode.

All areas generated by using the fo:region-body are of area-class "xsl-absolute".

Trait Derivation:

The reference-orientation of the region-viewport-area is taken from the value of the reference-orientation trait on the region-master which specifies the region. reference-orientation of the region-reference-area is set to "0" and is, therefore, the same as the orientation established by the region-viewport-area.

The remaining traits on the region-viewport-area and region-reference-area are set according to normal rules for determining the values of traits.

The traits on the span-reference-areas and on the normal-flow-reference-areas are determined, in the same manner as described in [5 Property Refinement / Resolution], from a set of properties where each property has its initial value except for reference-orientation, writing-mode, and display-align that have the value from the fo:region-body.

Constraints:

The constraints applicable to all regions (see [6.4.12 fo:simple-page-master]) all apply.

The inline-progression-dimension of the region-viewport-area is determined by the inline-progression-dimension of the content-rectangle of the page-reference-area minus the values of the start-indent and end-indent traits of the region-master. The start-edge and end-edge of the content-rectangle of the region-viewport-area are determined by the reference-orientation trait on the page-master.

The block-progression-dimension of the region-viewport-area is determined by the block-progression-dimension of the content-rectangle for the page-reference-area minus the values of the space-before and space-after traits of the region-master. The before-edge and after-edge of the content-rectangle of the region-viewport-area are determined by the reference-orientation trait on the page-master.

The values of the space-before and start-indent traits are used to position the region-viewport-area relative to the before-edge and start-edge of the content-rectangle of the page-reference-area.

The constraints on the size and position of the region-reference-area generated using the fo:region-body are covered in the "Constraints applicable to regions" section of [6.4.12 fo:simple-page-master].

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.7 Common Border, Padding, and Background Properties]
• [7.10 Common Margin Properties-Block]
• [7.20.1 "clip"]
• [7.25.2 "column-count"]
• [7.25.3 "column-gap"]
• [7.13.4 "display-align"]
• [7.20.2 "overflow"]
• [7.25.17 "region-name"]
• [7.20.3 "reference-orientation"]
• [7.27.7 "writing-mode"]

6.4.14 fo:region-before

Common Usage:

Used in constructing a simple-page-master. This region specifies a viewport/reference pair that is located on the "before" side of the page-reference-area. In lr-tb writing-mode, this region corresponds to the header region. The overflow trait controls how much of the underlying region-reference-area is visible; that is, whether the region-reference-area is clipped by its parent region-viewport-area.

Areas:

The fo:region-before formatting object is used to generate one region-viewport-area and one region-reference-area.

In version 1.0 of this Recommendation, the values of the padding and border-width traits must be "0".

The before-edge of the content-rectangle of this region-viewport-area is positioned coincident with the before-edge of the content-rectangle of the page-reference-area generated using the parent fo:simple-page-master. The block-progression-dimension of the region-viewport-area is determined by the extent trait on the fo:region-before formatting object.

The inline-progression-dimension of the region-viewport-area is determined by the precedence trait on the fo:region-before. If the value of the precedence trait is true, then the inline-progression-dimension extends up to the start-edge and end-edge of the content-rectangle of the page-reference-area. In this case, the region-before region-viewport-area acts like a float into areas generated by the region-start and region-end. If the value of the precedence trait on the fo:region-before is false, then these adjacent regions float into the area generated by the fo:region-before and the extent of the fo:region-before is (effectively) reduced by the incursions of the adjacent regions.

The region-reference-area lies on a canvas underneath the region-viewport-area. The reference-orientation trait is used to orient the coordinate system of the region-reference-area relative to the page-reference-area.

The size of the region-reference-area depends on the setting of the overflow trait on the region. If the value of that trait is "auto", "hidden", "error-if-overflow", "paginate", or "visible" then the size of the reference-area is the same as the size of the viewport. If the value of the overflow trait is "scroll", the size of the reference-area is equal to the size of the viewport in the inline-progression-direction in the writing-mode for the region and has no constraint in the block-progression-direction (which implies that it grows to hold the distribution of all the content bound to the region).

Trait Derivation:

The reference-orientation of the region-viewport-area is taken from the value of the reference-orientation trait on the region-master which specifies the region. reference-orientation of the region-reference-area is set to "0" and is, therefore, the same as the orientation established by the region-viewport-area.

The remaining traits on the region-viewport-area and region-reference-area are set according to normal rules for determining the values of traits.

Constraints:

The constraints on the size and position of the region-reference-area generated using the fo:region-before are covered in the "Constraints applicable to regions" section of [6.4.12 fo:simple-page-master].

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.7 Common Border, Padding, and Background Properties]
• [7.20.1 "clip"]
• [7.13.4 "display-align"]
• [7.25.4 "extent"]
• [7.20.2 "overflow"]
• [7.25.16 "precedence"]
• [7.25.17 "region-name"]
• [7.20.3 "reference-orientation"]
• [7.27.7 "writing-mode"]

6.4.15 fo:region-after

Common Usage:

Used in constructing a simple-page-master. This region specifies a viewport/reference pair that is located on the "after" side of the page-reference-area. In lr-tb writing-mode, this region corresponds to the footer region. The overflow trait controls how much of the underlying region-reference-area is visible; that is, whether the region-reference-area is clipped by its parent region-viewport-area.

Areas:

The fo:region-after formatting object is used to generate one region-viewport-area and one region-reference-area.

In version 1.0 of this Recommendation, the values of the padding and border-width traits must be "0".

The after-edge of the content-rectangle of this region-viewport-area is positioned coincident with the after-edge of the content-rectangle of the page-reference-area generated using the parent fo:simple-page-master. The block-progression-dimension of the region-viewport-area is determined by the extent trait on the fo:region-after formatting object.

The inline-progression-dimension of the region-viewport-area is determined by the precedence trait on the fo:region-after. If the value of the precedence trait is true, then the inline-progression-dimension extends up to the start-edge and end-edge of the content-rectangle of the page-reference-area. In this case, the region-after region-viewport-area acts like a float into areas generated by the region-start and region-end. If the value of the precedence trait on the fo:region-after is false, then these adjacent regions float into the area generated by the fo:region-after and the extent of the fo:region-after is (effectively) reduced by the incursions of the adjacent regions.

The region-reference-area lies on a canvas underneath the region-viewport-area. The reference-orientation trait is used to orient the coordinate system of the region-reference-area relative to the page-reference-area.

The size of the region-reference-area depends on the setting of the overflow trait on the region. If the value of that trait is "auto", "hidden", "error-if-overflow", "paginate", or "visible" then the size of the reference-area is the same as the size of the viewport. If the value of the overflow trait is "scroll", the size of the reference-area is equal to the size of the viewport in the inline-progression-direction in the writing-mode for the region and has no constraint in block-progression-direction (which implies that it grows to hold the distribution of all the content bound to the region).

Trait Derivation:

The reference-orientation of the region-viewport-area is taken from the value of the reference-orientation trait on the region-master which specifies the region. reference-orientation of the region-reference-area is set to "0" and is, therefore, the same as the orientation established by the region-viewport-area.

The remaining traits on the region-viewport-area and region-reference-area are set according to normal rules for determining the values of traits.

Constraints:

The constraints on the size and position of the region-reference-area generated using the fo:region-after are covered in the "Constraints applicable to regions" section of [6.4.12 fo:simple-page-master].

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.7 Common Border, Padding, and Background Properties]
• [7.20.1 "clip"]
• [7.13.4 "display-align"]
• [7.25.4 "extent"]
• [7.20.2 "overflow"]
• [7.25.16 "precedence"]
• [7.25.17 "region-name"]
• [7.20.3 "reference-orientation"]
• [7.27.7 "writing-mode"]

6.4.16 fo:region-start

Common Usage:

Used in constructing a simple-page-master. This region specifies a viewport/reference pair that is located on the "start" side of the page-reference-area. In lr-tb writing-mode, this region corresponds to a left sidebar. The overflow trait controls how much of the underlying region-reference-area is visible; that is, whether the region-reference-area is clipped by its parent region-viewport-area.

Areas:

The fo:region-start formatting object is used to generate one region-viewport-area and one region-reference-area.

In version 1.0 of this Recommendation, the values of the padding and border-width traits must be "0".

The start-edge of the content-rectangle of this region-viewport-area is positioned coincident with the start-edge of the content-rectangle of the page-reference-area generated using the parent fo:simple-page-master. The inline-progression-dimension of the region-viewport-area is determined by the extent trait on the fo:region-after formatting object.

The block-progression-dimension of the region-viewport-area is determined by the precedence trait on the adjacent fo:region-before and the fo:region-after, if these exist; otherwise it is determined as if the value of the precedence trait was false. If the value of the precedence trait of the fo:region-before (or, respectively, fo:region-after) is false, then the block-progression-dimension extends up to the before- (or, respectively, after-) edge of the content-rectangle of the page-reference-area. In this case, the region-start acts like a float into areas generated by the region-before (respectively, the region-after). If the value of the precedence trait on the adjacent regions is true, then these adjacent regions float into the area generated by the fo:region-start and the extent of the fo:region-start is (effectively) reduced by the incursions of the adjacent regions with the value of the precedence trait equal to true.

The region-reference-area lies on a canvas underneath the region-viewport-area. The reference-orientation trait is used to orient the coordinate system of the region-reference-area relative to the page-reference-area.

The size of the region-reference-area depends on the setting of the overflow trait on the region. If the value of that trait is "auto", "hidden", "error-if-overflow", "paginate", or "visible" then the size of the reference-area is the same as the size of the viewport. If the value of the overflow trait is "scroll", the size of the reference-area is equal to the size of the viewport in the inline-progression-direction in the writing-mode for the region and has no constraint in block-progression-direction (which implies that it grows to hold the distribution of all the content bound to the region).

Trait Derivation:

The reference-orientation of the region-viewport-area is taken from the value of the reference-orientation trait on the region-master which specifies the region. reference-orientation of the region-reference-area is set to "0" and is, therefore, the same as the orientation established by the region-viewport-area.

The remaining traits on the region-viewport-area and region-reference-area are set according to normal rules for determining the values of traits.

Constraints:

The constraints on the size and position of the region-reference-area generated using the fo:region-start are covered in the "Constraints applicable to regions" section of [6.4.12 fo:simple-page-master].

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.7 Common Border, Padding, and Background Properties]
• [7.20.1 "clip"]
• [7.13.4 "display-align"]
• [7.25.4 "extent"]
• [7.20.2 "overflow"]
• [7.25.17 "region-name"]
• [7.20.3 "reference-orientation"]
• [7.27.7 "writing-mode"]

6.4.17 fo:region-end

Common Usage:

Used in constructing a simple-page-master. This region specifies a viewport/reference pair that is located on the "end" side of the page-reference-area. In lr-tb writing-mode, this region corresponds to a right sidebar. The overflow trait controls how much of the underlying region-reference-area is visible; that is, whether the region-reference-area is clipped by its parent region-viewport-area.

Areas:

The fo:region-end formatting object is used to generate one region-viewport-area and one region-reference-area.

In version 1.0 of this Recommendation, the values of the padding and border-width traits must be "0".

The end-edge of the content-rectangle of this region-viewport-area is positioned coincident with the end-edge of the content-rectangle of the page-reference-area generated using the parent fo:simple-page-master. The inline-progression-dimension of the region-viewport-area is determined by the extent trait on the fo:region-after formatting object.

The block-progression-dimension of the region-viewport-area is determined by the precedence trait on the adjacent fo:region-before and the fo:region-after, if these exist; otherwise it is determined as if the value of the precedence trait was false. If the value of the precedence trait of the fo:region-before (or, respectively, fo:region-after) is false, then the block-progression-dimension extends up to the before- (or, respectively, after-) edge of the content-rectangle of the page-reference-area. In this case, the region-end acts like a float into areas generated by the region-before (respectively, the region-after). If the value of the precedence trait on the adjacent regions is true, then these adjacent regions float into the area generated by the fo:region-end and the extent of the fo:region-end is (effectively) reduced by the incursions of the adjacent regions with the value of the precedence trait equal to true.

The region-reference-area lies on a canvas underneath the region-viewport-area. The reference-orientation trait is used to orient the coordinate system of the region-reference-area relative to the page-reference-area.

The size of the region-reference-area depends on the setting of the overflow trait on the region. If the value of that trait is "auto", "hidden", "error-if-overflow", "paginate", or "visible" then the size of the reference-area is the same as the size of the viewport. If the value of the overflow trait is "scroll", the size of the reference-area is equal to the size of the viewport in the inline-progression-direction in the writing-mode for the region and has no constraint in block-progression-direction (which implies that it grows to hold the distribution of all the content bound to the region).

Trait Derivation:

The reference-orientation of the region-viewport-area is taken from the value of the reference-orientation trait on the region-master which specifies the region. reference-orientation of the region-reference-area is set to "0" and is, therefore, the same as the orientation established by the region-viewport-area.

The remaining traits on the region-viewport-area and region-reference-area are set according to normal rules for determining the values of traits.

Constraints:

The constraints on the size and position of the region-reference-area generated using the fo:region-end are covered in the "Constraints applicable to regions" section of [6.4.12 fo:simple-page-master].

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.7 Common Border, Padding, and Background Properties]
• [7.20.1 "clip"]
• [7.13.4 "display-align"]
• [7.25.4 "extent"]
• [7.20.2 "overflow"]
• [7.25.17 "region-name"]
• [7.20.3 "reference-orientation"]
• [7.27.7 "writing-mode"]

6.4.18 fo:flow

Common Usage:

The content of the fo:flow formatting object is a sequence of flow objects that provides the flowing text content that is distributed into pages.

Areas:

The fo:flow formatting object does not generate any areas. The fo:flow formatting object returns a sequence of areas created by concatenating the sequences of areas returned by each of the children of the fo:flow. The order of concatenation is the same order as the children are ordered under the fo:flow.

Constraints:

The (implicit) flow-map determines the assignment of the content of the fo:flow to a region.

Contents:

(%block;)+

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.25.5 "flow-name"]

6.4.19 fo:static-content

Common Usage:

The fo:static-content formatting object holds a sequence or a tree of formatting objects that is to be presented in a single region or repeated in like-named regions on one or more pages in the page-sequence. Its common use is for repeating or running headers and footers.

This content is repeated, in its entirety, on every page to which it is assigned.

Areas:

The fo:static-content formatting object does not generate any areas. The fo:static-content formatting object returns the sequence of areas created by concatenating the sequences of areas returned by each of the children of the fo:static-content. The order of concatenation is the same order as the children are ordered under the fo:static-content.

Constraints:

The (implicit) flow-map determines the assignment of the content of the fo:static-content to a region.

The fo:static-content may be processed multiple times and thus the default ordering constraint of section [4.7.1 General Ordering Constraints] does not apply to the fo:static-content. Instead, it must satisfy the constraint on a per-page basis. Specifically, if P is a page-reference-area, C is an area-class, and S is the set of all descendants of P of area-class C returned to the fo:static-content descendant, then S must be properly-ordered.

Contents:

(%block;)+

The following properties apply to this formatting object:

• [7.25.5 "flow-name"]

6.4.20 fo:title

Common Usage:

The fo:title formatting object is used to associate a title with a given page-sequence. This title may be used by an interactive User Agent to identify the pages. For example, the content of the fo:title can be formatted and displayed in a "title" window or in a "tool tip".

Areas:

This formatting object returns the sequence of areas returned by the children of this formatting object.

Constraints:

The sequence of returned areas must be the concatenation of the sub-sequences of areas returned by each of the flow children of the fo:title formatting object in the order in which the children occur.

Contents:

(#PCDATA|%inline;)*

An fo:title is not permitted to have an fo:float, fo:footnote or fo:marker as a descendant.

Additionally, an fo:title is not permitted to have as a descendant an fo:block-container that generates an absolutely positioned area.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.8 Common Font Properties]
• [7.11 Common Margin Properties-Inline]
• [7.17.1 "color"]
• [7.15.4 "line-height"]
• [7.28.8 "visibility"]

6.5 Block-level Formatting Objects

6.5.1 Introduction

The fo:block formatting object is used for formatting paragraphs, titles, figure captions, table titles, etc. The following example illustrates the usage of the fo:block in a style sheet.

6.5.1.1 Example

6.5.1.1.1 Chapter and Section Titles, Paragraphs

Input sample:

<doc>
  <chapter>
    <title>Chapter title</title>
    <section>
      <title>First section title</title>
      <paragraph>Section one's first paragraph.</paragraph>
      <paragraph>Section one's second paragraph.</paragraph>
    </section>
    <section>
      <title>Second section title</title>
      <paragraph>Section two's only paragraph.</paragraph>
    </section>
  </chapter>
</doc>

In this example the chapter title appears at the top of the page (its "space-before" is discarded).

Space between chapter title and first section title is (8pt,8pt,8pt): the chapter title's "space-after" has a higher precedence than the section title's "space-before" (which takes on the initial value of zero), so the latter is discarded.

Space between the first section title and section one's first paragraph is (6pt,6pt,6pt): the section title's "space-after" has higher precedence than the paragraph's "space-before", so the latter is discarded.

Space between the two paragraphs is (6pt,8pt,10pt): the "space-after" the first paragraph is discarded because its precedence is equal to that of the "space-before" the next paragraph, and the optimum of the "space-after" of the first paragraph is greater than the optimum of the "space-before" of the second paragraph.

Space between the second paragraph of the first section and the title of the second section is (12pt,12pt,12pt): the "space-after" the paragraph is discarded because its precedence is equal to that of the "space-before" of the section title, and the optimum of the "space-after" of the paragraph is less than the optimum of the "space-before" of the section title.

The indent on the first line of the first paragraph in section one and the only paragraph in section two is zero; the indent on the first line of the second paragraph in section one is 2pc.

XSL Stylesheet:

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:fo="http://www.w3.org/1999/XSL/Format">

<xsl:template match="chapter">
  <fo:block break-before="page">
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="chapter/title">
  <fo:block text-align="center" space-after="8pt"
            space-before="16pt" space-after.precedence="3">
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="section">
  <xsl:apply-templates/>
</xsl:template>

<xsl:template match="section/title">
  <fo:block text-align="center" space-after="6pt"
            space-before="12pt" space-before.precedence="0"
            space-after.precedence="3">
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="paragraph[1]" priority="1">
  <fo:block text-indent="0pc" space-after="7pt"
            space-before.minimum="6pt" space-before.optimum="8pt"
            space-before.maximum="10pt">
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="paragraph">
  <fo:block text-indent="2pc" space-after="7pt"
            space-before.minimum="6pt" space-before.optimum="8pt"
            space-before.maximum="10pt">
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

</xsl:stylesheet>

Result Instance: elements and attributes in the fo: namespace

<fo:block break-before="page">

  <fo:block text-align="center" space-after="8pt"
    space-before="16pt"
    space-after.precedence="3">Chapter title
  </fo:block>

  <fo:block text-align="center" space-after="6pt"
    space-before="12pt" space-before.precedence="0"
    space-after.precedence="3">First section title
  </fo:block>

  <fo:block text-indent="0pc" space-after="7pt"
    space-before.minimum="6pt" space-before.optimum="8pt"
    space-before.maximum="10pt">Section one's first paragraph.
  </fo:block>

  <fo:block text-indent="2pc" space-after="7pt"
    space-before.minimum="6pt" space-before.optimum="8pt"
    space-before.maximum="10pt">Section one's second paragraph.
  </fo:block>

  <fo:block text-align="center" space-after="6pt"
    space-before="12pt" space-before.precedence="0"
    space-after.precedence="3">Second section title
  </fo:block>

  <fo:block text-indent="0pc" space-after="7pt"
    space-before.minimum="6pt" space-before.optimum="8pt"
    space-before.maximum="10pt">Section two's only paragraph.
  </fo:block>

</fo:block>

6.5.2 fo:block

Common Usage:

The fo:block formatting object is commonly used for formatting paragraphs, titles, headlines, figure and table captions, etc.

Areas:

The fo:block formatting object generates one or more normal block-areas. The fo:block returns these areas, any page-level-out-of-line areas, and any reference-level-out-of-line areas returned by the children of the fo:block. The fo:block also generates zero or more line-areas as children of the normal block-areas it returns, in accordance with [4.7.2 Line-building].

Trait Derivation:

The .minimum, .optimum, and .maximum components of the half-leading trait are set to 1/2 the difference of the computed value of the line-height property and the computed value of the sum of the text-altitude and text-depth properties. The .precedence and .conditionality components are copied from the line-height property.

NOTE:

The usage of the half-leading is described in [4.5 Line-areas].

Constraints:

No area may have more than one normal child area returned by the same fo:block formatting object.

The children of each normal area generated by an fo:block must satisfy the constraints specified in [4.7.2 Line-building].

In addition the constraints imposed by the traits derived from the properties applicable to this formatting object must be satisfied. The geometric constraints are rigorously defined in [4 Area Model].

Contents:

(#PCDATA|%inline;|%block;)*

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children, optionally followed by an fo:initial-property-set.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.8 Common Font Properties]
• [7.9 Common Hyphenation Properties]
• [7.10 Common Margin Properties-Block]
• [7.12 Common Relative Position Properties]
• [7.19.1 "break-after"]
• [7.19.2 "break-before"]
• [7.17.1 "color"]
• [7.27.5 "text-depth"]
• [7.27.4 "text-altitude"]
• [7.15.1 "hyphenation-keep"]
• [7.15.2 "hyphenation-ladder-count"]
• [7.28.2 "id"]
• [7.18.3 "intrusion-displace"]
• [7.19.3 "keep-together"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.15.3 "last-line-end-indent"]
• [7.15.7 "linefeed-treatment"]
• [7.15.4 "line-height"]
• [7.15.5 "line-height-shift-adjustment"]
• [7.15.6 "line-stacking-strategy"]
• [7.19.6 "orphans"]
• [7.15.8 "white-space-treatment"]
• [7.20.4 "span"]
• [7.15.9 "text-align"]
• [7.15.10 "text-align-last"]
• [7.15.11 "text-indent"]
• [7.28.8 "visibility"]
• [7.15.12 "white-space-collapse"]
• [7.19.7 "widows"]
• [7.15.13 "wrap-option"]

6.5.3 fo:block-container

Common Usage:

The fo:block-container flow object is used to generate a block-level reference-area, typically containing text blocks with a different writing-mode. In addition, it can also be used with a different reference-orientation to rotate its content.

NOTE:

The use of this flow object is not required for changing the inline-progression-direction only; in that case the Unicode bidi algorithm and the fo:bidi-override are sufficient.

Areas:

The fo:block-container formatting object generates one or more viewport/reference pairs. The fo:block-container returns these areas and any page-level-out-of-line areas returned by the children of the fo:block-container.

Trait Derivation:

The areas generated by the fo:block-container formatting object have a value of "true" for the is-reference-area.

The size of the viewport-area and the reference-area has to be fixed in the inline-progression-direction. It must be specified unless the inline-progression-direction is parallel to the inline-progression-direction of the reference-area into which the areas generated by this flow object are placed.

Constraints:

The children of each reference-area generated by an fo:block-container formatting object must be normal block-areas returned by the children of the fo:block-container, must be properly stacked, and must be properly ordered.

Any reference-level-out-of-line areas returned by the children of the fo:block-container are handled as described in [6.10.2 fo:float].

Contents:

(%block;)+

In addition an fo:block-container that does not generate an absolutely positioned area may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.5 Common Absolute Position Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.10 Common Margin Properties-Block]
• [7.14.1 "block-progression-dimension"]
• [7.19.1 "break-after"]
• [7.19.2 "break-before"]
• [7.20.1 "clip"]
• [7.13.4 "display-align"]
• [7.14.4 "height"]
• [7.28.2 "id"]
• [7.14.5 "inline-progression-dimension"]
• [7.18.3 "intrusion-displace"]
• [7.19.3 "keep-together"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.20.2 "overflow"]
• [7.20.3 "reference-orientation"]
• [7.20.4 "span"]
• [7.14.12 "width"]
• [7.27.7 "writing-mode"]
• [7.28.9 "z-index"]

6.6 Inline-level Formatting Objects

6.6.1 Introduction

Inline-level formatting objects are most commonly used to format a portion of text or for generating rules and leaders. There are many other uses. The following examples illustrate some of these uses of inline-level formatting objects.

• putting the first line of a paragraph into small-caps,

• turning a normally inline formatting object, fo:external-graphic, into a block by "wrapping" with an fo:block formatting object,

• formatting a running footer containing the word "Page" followed by a page number.

6.6.1.1 Examples

6.6.1.1.1 First Line of Paragraph in Small-caps

Input sample:

<doc>
<p>This is the text of a paragraph that is going to be
presented with the first line in small-caps.</p>
</doc>

XSL Stylesheet:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fo="http://www.w3.org/1999/XSL/Format"
                version='1.0'>

<xsl:template match="p">
  <fo:block>
    <fo:initial-property-set font-variant="small-caps"/>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

</xsl:stylesheet>

Result instance: elements and attributes in the fo: namespace

<fo:block>
  <fo:initial-property-set font-variant="small-caps">
  </fo:initial-property-set>This is the text of a paragraph that is going to be
presented with the first line in small-caps.
</fo:block>

6.6.1.1.2 Figure with a Photograph

Input sample:

<doc>
  <figure>
    <photo image="TH0317A.jpg"/>
    <caption>C'ieng Tamlung of C'ieng Mai</caption>
  </figure>
</doc>

In this example the image (an fo:external-graphic) is placed as a centered block-level object. The caption is centered with 10mm indents.

XSL Stylesheet:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fo="http://www.w3.org/1999/XSL/Format"
                version='1.0'>

<xsl:template match="figure">
  <fo:block>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="photo">
  <fo:block text-align="center">
    <fo:external-graphic src="{@image}"/>
  </fo:block>
</xsl:template>

<xsl:template match="caption">
  <fo:block space-before="3pt" text-align="center"
    start-indent="10mm" end-indent="10mm">
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

</xsl:stylesheet>

fo: element and attribute tree:

<fo:block>
  <fo:block text-align="center">
    <fo:external-graphic src="TH0317A.jpg"/>
  </fo:block>

  <fo:block space-before="3pt" text-align="center" start-indent="10mm"
    end-indent="10mm">C'ieng Tamlung of C'ieng Mai</fo:block>
</fo:block>

6.6.1.1.3 Page numbering and page number reference

Input sample:

<!DOCTYPE doc SYSTEM "pgref.dtd">
<doc>
  <chapter id="x"><title>Chapter</title>
    <p>Text</p>
  </chapter>
  <chapter><title>Chapter</title>
    <p>For a description of X see <ref refid="x"/>.</p>
  </chapter>
</doc>

In this example each page has a running footer containing the word "Page" followed by the page number. The "ref" element generates the word "page" followed by the page number of the page on which the referenced by the "refid" attribute was placed.

XSL Stylesheet:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fo="http://www.w3.org/1999/XSL/Format"
                version='1.0'>

<xsl:template match="doc">
  <fo:root>
    <fo:layout-master-set>
      <fo:simple-page-master master-name="page"
        page-height="297mm" page-width="210mm"
        margin-top="20mm" margin-bottom="10mm"
        margin-left="25mm" margin-right="25mm">
        <fo:region-body
          margin-top="0mm" margin-bottom="15mm"
          margin-left="0mm" margin-right="0mm"/>
        <fo:region-after extent="10mm"/>
      </fo:simple-page-master>
    </fo:layout-master-set>
    <fo:page-sequence master-reference="page">
      <fo:static-content flow-name="xsl-region-after">
        <fo:block>
          <xsl:text>Page </xsl:text>
          <fo:page-number/>
        </fo:block>
      </fo:static-content>
      <fo:flow flow-name="xsl-region-body">
        <xsl:apply-templates/>
      </fo:flow>
    </fo:page-sequence>
  </fo:root>
</xsl:template>

<xsl:template match="chapter/title">
  <fo:block id="{generate-id(.)}">
    <xsl:number level="multiple" count="chapter" format="1. "/>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="p">
  <fo:block>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="ref">
  <xsl:text>page </xsl:text>
  <fo:page-number-citation refid="{generate-id(id(@refid)/title)}"/>
</xsl:template>

</xsl:stylesheet>

Result Instance: elements and attributes in the fo: namespace

<fo:root>
  <fo:layout-master-set>
    <fo:simple-page-master master-name="page"
      page-height="297mm" page-width="210mm"
      margin-top="20mm" margin-bottom="10mm"
      margin-left="25mm" margin-right="25mm">
      <fo:region-body margin-top="0mm" margin-bottom="15mm"
        margin-left="0mm" margin-right="0mm"/>
      <fo:region-after extent="10mm"/>
    </fo:simple-page-master>
  </fo:layout-master-set>
  <fo:page-sequence master-reference="page">
    <fo:static-content flow-name="xsl-region-after">
      <fo:block>Page <fo:page-number/>
      </fo:block>
    </fo:static-content>
    <fo:flow flow-name="xsl-region-body">
      <fo:block id="N5">1. Chapter</fo:block>
      <fo:block>Text</fo:block>
      <fo:block id="N13">2. Chapter</fo:block>
      <fo:block>For a description of X see page <fo:page-number-citation refid="N5"/>
      </fo:block>
    </fo:flow>
  </fo:page-sequence>
</fo:root>

6.6.1.1.4 Table of Contents with Leaders

Input sample:

<doc>
  <chapter><title>Chapter</title>
    <p>Text</p>
    <section><title>Section</title>
    <p>Text</p>
    </section>
    <section><title>Section</title>
    <p>Text</p>
    </section>
  </chapter>
  <chapter><title>Chapter</title>
    <p>Text</p>
    <section><title>Section</title>
    <p>Text</p>
    </section>
    <section><title>Section</title>
    <p>Text</p>
    </section>
  </chapter>
</doc>

In this example the table of contents is formatted with a dot leader between the heading text and the page number.

XSL Stylesheet:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fo="http://www.w3.org/1999/XSL/Format"
                version='1.0'>

<xsl:template match="doc">
  <!-- create the table of contents -->
  <xsl:apply-templates select="chapter/title" mode="toc"/>
  <!-- do the document -->
  <xsl:apply-templates/>
</xsl:template>

<xsl:template match="chapter/title" mode="toc">
  <fo:block text-align-last="justify">
    <fo:simple-link internal-destination="{generate-id(.)}">
      <xsl:number level="multiple" count="chapter" format="1. "/>
      <xsl:apply-templates/>
    </fo:simple-link>
    <xsl:text> </xsl:text>
    <fo:leader leader-length.minimum="12pt" leader-length.optimum="40pt"
               leader-length.maximum="100%" leader-pattern="dots"/>
    <xsl:text> </xsl:text>
    <fo:page-number-citation ref-id="{generate-id(.)}"/>
  </fo:block>
  <xsl:apply-templates select="../section/title" mode="toc"/>
</xsl:template>

<xsl:template match="section/title" mode="toc">
  <fo:block start-indent="10mm" text-align-last="justify">
    <fo:simple-link internal-destination="{generate-id(.)}">
      <xsl:number level="multiple" count="chapter|section" format="1.1 "/>
      <xsl:apply-templates/>
    </fo:simple-link>
    <xsl:text> </xsl:text>
    <fo:leader leader-length.minimum="12pt" leader-length.optimum="40pt"
               leader-length.maximum="100%" leader-pattern="dots"/>
    <xsl:text> </xsl:text>
    <fo:page-number-citation ref-id="{generate-id(.)}"/>
  </fo:block>
</xsl:template>

<xsl:template match="chapter/title">
  <fo:block id="{generate-id(.)}">
    <xsl:number level="multiple" count="chapter" format="1. "/>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="section/title">
  <fo:block id="{generate-id(.)}">
    <xsl:number level="multiple" count="chapter|section" format="1.1 "/>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="p">
  <fo:block>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

</xsl:stylesheet>

Result Instance: elements and attributes in the fo: namespace

<fo:block text-align-last="justify">
  <fo:simple-link internal-destination="N4">1. Chapter
  </fo:simple-link>
  <fo:leader leader-length.minimum="12pt" leader-length.optimum="40pt"
    leader-length.maximum="100%" leader-pattern="dots">
  </fo:leader>
  <fo:page-number-citation ref-id="N4">
  </fo:page-number-citation>
</fo:block>
<fo:block start-indent="10mm" text-align-last="justify">
  <fo:simple-link internal-destination="N11">1.1 Section
  </fo:simple-link>
  <fo:leader leader-length.minimum="12pt" leader-length.optimum="40pt"
    leader-length.maximum="100%" leader-pattern="dots">
  </fo:leader>
  <fo:page-number-citation ref-id="N11">
  </fo:page-number-citation>
</fo:block>
<fo:block start-indent="10mm" text-align-last="justify">
  <fo:simple-link internal-destination="N19">1.2 Section
  </fo:simple-link>
  <fo:leader leader-length.minimum="12pt" leader-length.optimum="40pt"
    leader-length.maximum="100%" leader-pattern="dots">
  </fo:leader>
  <fo:page-number-citation ref-id="N19">
  </fo:page-number-citation>
</fo:block>
<fo:block text-align-last="justify">
  <fo:simple-link internal-destination="N28">2. Chapter
  </fo:simple-link>
  <fo:leader leader-length.minimum="12pt" leader-length.optimum="40pt"
    leader-length.maximum="100%" leader-pattern="dots">
  </fo:leader>
  <fo:page-number-citation ref-id="N28">
  </fo:page-number-citation>
</fo:block>
<fo:block start-indent="10mm" text-align-last="justify">
  <fo:simple-link internal-destination="N35">2.1 Section
  </fo:simple-link>
  <fo:leader leader-length.minimum="12pt" leader-length.optimum="40pt"
    leader-length.maximum="100%" leader-pattern="dots">
  </fo:leader>
  <fo:page-number-citation ref-id="N35">
  </fo:page-number-citation>
</fo:block>
<fo:block start-indent="10mm" text-align-last="justify">
  <fo:simple-link internal-destination="N43">2.2 Section
  </fo:simple-link>
  <fo:leader leader-length.minimum="12pt" leader-length.optimum="40pt"
    leader-length.maximum="100%" leader-pattern="dots">
  </fo:leader>
  <fo:page-number-citation ref-id="N43">
  </fo:page-number-citation>
</fo:block>

<fo:block id="N4">1. Chapter
</fo:block>

<fo:block>Text
</fo:block>

<fo:block id="N11">1.1 Section
</fo:block>

<fo:block>Text
</fo:block>

<fo:block id="N19">1.2 Section
</fo:block>

<fo:block>Text
</fo:block>

<fo:block id="N28">2. Chapter
</fo:block>

<fo:block>Text
</fo:block>

<fo:block id="N35">2.1 Section
</fo:block>

<fo:block>Text
</fo:block>

<fo:block id="N43">2.2 Section
</fo:block>

<fo:block>Text
</fo:block>

6.6.2 fo:bidi-override

Common Usage:

The fo:bidi-override formatting object is used when the Unicode-bidi algorithm fails. It forces a string of text to be written in a specific direction.

Areas:

The fo:bidi-override formatting object generates one or more normal inline-areas. The fo:bidi-override returns these areas, any page-level-out-of-line areas, and any reference-level-out-of-line areas returned by the children of the fo:bidi-override.

Trait Derivation:

The direction traits are derived from the "writing-mode", "direction", and "unicode-bidi" properties as described in [5.5.3 Writing-mode and Direction Properties].

Constraints:

No area may have more than one normal child area returned by the same fo:bidi-override formatting object.

The children of each normal area returned by an fo:bidi-override must satisfy the constraints specified in [4.7.3 Inline-building].

Contents:

(#PCDATA|%inline;|%block;)*

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

An fo:bidi-override that is a descendant of an fo:leader or of an fo:inline child of an fo:footnote may not have block-level children, unless it has a nearer ancestor that is an fo:inline-container.

The following properties apply to this formatting object:

• [7.6 Common Aural Properties]
• [7.8 Common Font Properties]
• [7.12 Common Relative Position Properties]
• [7.17.1 "color"]
• [7.27.1 "direction"]
• [7.28.2 "id"]
• [7.16.2 "letter-spacing"]
• [7.15.4 "line-height"]
• [7.28.6 "score-spaces"]
• [7.27.6 "unicode-bidi"]
• [7.16.8 "word-spacing"]

6.6.3 fo:character

Common Usage:

The fo:character flow object represents a character that is mapped to a glyph for presentation. It is an atomic unit to the formatter.

When the result tree is interpreted as a tree of formatting objects, a character in the result tree is treated as if it were an empty element of type fo:character with a character attribute equal to the Unicode representation of the character. The semantics of an "auto" value for character properties, which is typically their initial value, are based on the Unicode code point. Overrides may be specified in an implementation-specific manner.

NOTE:

In a stylesheet the explicit creation of an fo:character may be used to explicitly override the default mapping.

Unicode Tag Characters need not be supported.

NOTE:

Unicode Version 3.1, in fact, states that they are not to be used "with any protocols that provide alternate means for language tagging, such as HTML or XML.". Unicode TR20 ([UNICODE TR20]) also declares very clearly that they are not suitable together with markup.

Areas:

The fo:character formatting object generates and returns one or more normal inline-area.

NOTE:

Cases where more than one inline-area is generated are encountered in scripts where a single character generates both a prefix and a suffix glyph to some other character.

Constraints:

The dimensions of the areas are determined by the font metrics for the glyph.

When formatting an fo:character with a "treat-as-word-space" value of "true", the User Agent may use a different method for determining the inline-progression-dimension of the area.

NOTE:

Such methods typically make use of a word space value stored in the font, or a formatter defined word space value.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.8 Common Font Properties]
• [7.9 Common Hyphenation Properties]
• [7.11 Common Margin Properties-Inline]
• [7.12 Common Relative Position Properties]
• [7.13.1 "alignment-adjust"]
• [7.16.7 "treat-as-word-space"]
• [7.13.2 "alignment-baseline"]
• [7.13.3 "baseline-shift"]
• [7.16.1 "character"]
• [7.17.1 "color"]
• [7.13.5 "dominant-baseline"]
• [7.27.5 "text-depth"]
• [7.27.4 "text-altitude"]
• [7.27.2 "glyph-orientation-horizontal"]
• [7.27.3 "glyph-orientation-vertical"]
• [7.28.2 "id"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.16.2 "letter-spacing"]
• [7.15.4 "line-height"]
• [7.28.6 "score-spaces"]
• [7.16.3 "suppress-at-line-break"]
• [7.16.4 "text-decoration"]
• [7.16.5 "text-shadow"]
• [7.16.6 "text-transform"]
• [7.28.8 "visibility"]
• [7.16.8 "word-spacing"]

6.6.4 fo:initial-property-set

Common Usage:

The fo:initial-property-set auxiliary formatting object specifies formatting properties for the first line of an fo:block.

NOTE:

It is analogous to the CSS first-line pseudo-element.

In future versions of this Recommendation a property controlling the number of lines, or the "depth" that these initial properties apply to may be added.

Areas:

The fo:initial-property-set formatting object does not generate or return any areas. It simply holds a set of traits that are applicable to the first line-area of the area that has a value of "true" for the is-first trait and that was generated by the parent fo:block of the fo:initial-property-set.

Trait Derivation:

The traits on the fo:initial-property-set are taken into account as traits constraining the first line as if the child inline formatting objects of the fo:block, or parts of them in the case of a line-break, that were used in formatting the first line were enclosed by an fo:wrapper, as a direct child of the fo:block, with those traits.

Constraints:

None.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.8 Common Font Properties]
• [7.12 Common Relative Position Properties]
• [7.17.1 "color"]
• [7.28.2 "id"]
• [7.16.2 "letter-spacing"]
• [7.15.4 "line-height"]
• [7.28.6 "score-spaces"]
• [7.16.4 "text-decoration"]
• [7.16.5 "text-shadow"]
• [7.16.6 "text-transform"]
• [7.16.8 "word-spacing"]

6.6.5 fo:external-graphic

Common Usage:

The fo:external-graphic flow object is used for a graphic where the graphics data resides outside of the fo:element tree.

Areas:

The fo:external-graphic formatting object generates and returns one inline-level viewport-area and one reference-area containing the external graphic. The inline-level area uses the large-allocation-rectangle as defined in [4.2.3 Geometric Definitions].

NOTE:

An fo:external-graphic may be placed block-level by enclosing it in an fo:block.

A "line-stacking-strategy" of "max-height" or "line-height" is typicaly used for stacking one or more lines with fo:external-graphic content.

Constraints:

The viewport's size is determined by the block-progression-dimension and inline-progression-dimension traits. For values of "auto", the content size of the graphic is used.

The content size of a graphic is determined by taking the intrinsic size of the graphic and scaling as specified by the content-height, content-width, and scaling traits. If one of the content-height or content-width is not "auto", the same scale factor (as calculated from the specified non-auto value) is applied equally to both directions.

Once scaled, the reference-area is aligned with respect to the viewport-area using the text-align and display-align traits. If it is too large for the viewport-area, the graphic is aligned as if it would fit and the overflow trait controls the clipping, scroll bars, etc.

In the case when the graphics format does not specify an intrinsic size of the graphic the size is determined in an implementation-defined manner.

NOTE:

For example, a size of 1/96" as the size of one pixel for rasterized images may be used.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.11 Common Margin Properties-Inline]
• [7.12 Common Relative Position Properties]
• [7.13.1 "alignment-adjust"]
• [7.13.2 "alignment-baseline"]
• [7.13.3 "baseline-shift"]
• [7.14.1 "block-progression-dimension"]
• [7.14.2 "content-height"]
• [7.28.1 "content-type"]
• [7.14.3 "content-width"]
• [7.13.4 "display-align"]
• [7.13.5 "dominant-baseline"]
• [7.14.4 "height"]
• [7.28.2 "id"]
• [7.14.5 "inline-progression-dimension"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.15.4 "line-height"]
• [7.20.2 "overflow"]
• [7.14.10 "scaling"]
• [7.14.11 "scaling-method"]
• [7.28.7 "src"]
• [7.15.9 "text-align"]
• [7.14.12 "width"]

6.6.6 fo:instream-foreign-object

Common Usage:

The fo:instream-foreign-object flow object is used for an inline graphic or other "generic" object where the object data resides as descendants of the fo:instream-foreign-object, typically as an XML element subtree in a non-XSL namespace.

NOTE:

A common format is SVG.

Areas:

The fo:instream-foreign-object formatting object generates and returns one inline viewport-area and one reference-area containing the instream-foreign-object. The inline-level area uses the large-allocation-rectangle as defined in [4.2.3 Geometric Definitions].

Constraints:

The viewport's size is determined by the block-progression-dimension and inline-progression-dimension traits. For values of "auto", the content size of the instream foreign object is used.

The content size of an instream-foreign-object is determined by taking the intrinsic size of the object and scaling as specified by the content-height, content-width, and scaling traits. If one of the content-height or content-width is not "auto", the same scale factor (as calculated from the specified non-auto value) is applied equally to both directions.

Once scaled, the reference-area is aligned with respect to the viewport-area using the text-align and display-align traits. If it is too large for the viewport-area, the instream-foreign-object is aligned as if it would fit and the overflow trait controls the clipping, scroll bars, etc.

In the case when the instream-foreign-object does not specify an intrinsic size of the object, the size is determined in an implementation defined manner.

Contents:

The fo:instream-foreign-object flow object has a child from a non-XSL namespace. The permitted structure of this child is that defined for that namespace.

The fo:instream-foreign-object flow object may have additional attributes in the non-XSL namespace. These, as well as the xsl defined properties, are made available to the processor of the content of the flow object. Their semantics is defined by that namespace.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.11 Common Margin Properties-Inline]
• [7.12 Common Relative Position Properties]
• [7.13.1 "alignment-adjust"]
• [7.13.2 "alignment-baseline"]
• [7.13.3 "baseline-shift"]
• [7.14.1 "block-progression-dimension"]
• [7.14.2 "content-height"]
• [7.28.1 "content-type"]
• [7.14.3 "content-width"]
• [7.13.4 "display-align"]
• [7.13.5 "dominant-baseline"]
• [7.14.4 "height"]
• [7.28.2 "id"]
• [7.14.5 "inline-progression-dimension"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.15.4 "line-height"]
• [7.20.2 "overflow"]
• [7.14.10 "scaling"]
• [7.14.11 "scaling-method"]
• [7.15.9 "text-align"]
• [7.14.12 "width"]

6.6.7 fo:inline

Common Usage:

The fo:inline formatting object is commonly used for formatting a portion of text with a background or enclosing it in a border.

Areas:

The fo:inline formatting object generates one or more normal inline-areas. The fo:inline returns these areas, any page-level-out-of-line areas, and any reference-level-out-of-line areas returned by the children of the fo:inline.

Constraints:

No area may have more than one normal child area returned by the same fo:inline formatting object.

The children of each normal area returned by an fo:inline must satisfy the constraints specified in [4.7.3 Inline-building].

In addition the constraints imposed by the traits derived from the properties applicable to this formatting object must be satisfied. The geometric constraints are rigorously defined in [4 Area Model].

Contents:

(#PCDATA|%inline;|%block;)*

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

An fo:inline that is a child of an fo:footnote may not have block-level children. An fo:inline that is a descendant of an fo:leader or of the fo:inline child of an fo:footnote may not have block-level children, unless it has a nearer ancestor that is an fo:inline-container.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.8 Common Font Properties]
• [7.11 Common Margin Properties-Inline]
• [7.12 Common Relative Position Properties]
• [7.13.1 "alignment-adjust"]
• [7.13.2 "alignment-baseline"]
• [7.13.3 "baseline-shift"]
• [7.14.1 "block-progression-dimension"]
• [7.17.1 "color"]
• [7.13.5 "dominant-baseline"]
• [7.14.4 "height"]
• [7.28.2 "id"]
• [7.14.5 "inline-progression-dimension"]
• [7.19.3 "keep-together"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.15.4 "line-height"]
• [7.16.4 "text-decoration"]
• [7.28.8 "visibility"]
• [7.14.12 "width"]
• [7.15.13 "wrap-option"]

6.6.8 fo:inline-container

Common Usage:

The fo:inline-container flow object is used to generate an inline reference-area, typically containing text blocks with a different writing-mode.

NOTE:

The use of this flow object is not required for bi-directional text; in this case the Unicode BIDI algorithm and the fo:bidi-override are sufficient.

Areas:

The fo:inline-container formatting object generates one or more viewport/reference pairs. The viewport-areas generated by the fo:inline-container are normal inline-level areas that use the large-allocation-rectangle as defined in [4.2.3 Geometric Definitions]. The fo:inline-container returns these areas and any page-level-out-of-line areas returned by the children of the fo:inline-container.

Trait Derivation:

The areas generated by the fo:inline-container formatting object have a value of "true" for the is-reference-area.

The size of the viewport-area and the reference-area has to be fixed in the inline-progression-direction. It must be specified unless the inline-progression-direction is parallel to the inline-progression-direction of the reference-area into which the areas generated by this flow object are placed.

The values in the baseline-table of this object are calculated as follows:

baseline

If the writing mode has a block-progression-direction that is parallel to the block-progression-direction of the parent: the alignment-point is at the position of the dominant-baseline of the first descendant line-area. If there is no such line-area the alignment-point is at the position of the after-edge of the allocation rectangle.

If the writing mode has a block-progression-direction that is not parallel to the block-progression-direction of the parent: the alignment-point is at the position that is half way between the before-edge and after-edge of the content rectangle.

before-edge

The alignment-point is at the position of the before-edge of the allocation rectangle.

text-before-edge

The alignment-point is at the position that is the closest to the before-edge of the allocation rectangle selected from the two candidate edges. If the writing mode has a block-progression-direction that is parallel to the block-progression-direction of the parent the candidate edges are the before-edge and the after-edge of the content rectangle; if it is not, the candidate edges are the start-edge and the end-edge of the content rectangle.

middle

The alignment-point is at the position that is half way between the before-edge and after-edge of the allocation rectangle.

after-edge

The alignment-point is at the position of the after-edge of the allocation rectangle.

text-after-edge

The alignment-point is at the position that is the closest to the after-edge of the allocation rectangle selected from the two candidate edges. If the writing mode has a block-progression-direction that is parallel to the block-progression-direction of the parent the candidate edges are the before-edge and the after-edge of the content rectangle; if it is not, the candidate edges are the start-edge and the end-edge of the content rectangle.

ideographic

The alignment-point is at the position that is 7/10 of the distance from the before-edge of the allocation rectangle to the after-edge of the allocation rectangle.

alphabetic

The alignment-point is at the position that is 6/10 of the distance from the before-edge of the allocation rectangle to the after-edge of the allocation rectangle.

hanging

The alignment-point is at the position that is 2/10 of the distance from the before-edge of the allocation rectangle to the after-edge of the allocation rectangle.

mathematical

The alignment-point is at the position that is 5/10 of the distance from the before-edge of the allocation rectangle to the after-edge of the allocation rectangle.

Constraints:

No area may have more than one normal child area returned by the same fo:inline-container formatting object.

The children of each reference-area generated by an fo:inline-container formatting object must be normal block-areas returned by the children of the fo:inline-container, must be properly stacked, and must be properly ordered.

Any reference-level-out-of-line areas returned by the children of the fo:inline-container are handled as described in [6.10.2 fo:float].

Contents:

(%block;)+

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.7 Common Border, Padding, and Background Properties]
• [7.11 Common Margin Properties-Inline]
• [7.12 Common Relative Position Properties]
• [7.13.1 "alignment-adjust"]
• [7.13.2 "alignment-baseline"]
• [7.13.3 "baseline-shift"]
• [7.14.1 "block-progression-dimension"]
• [7.20.1 "clip"]
• [7.13.4 "display-align"]
• [7.13.5 "dominant-baseline"]
• [7.14.4 "height"]
• [7.28.2 "id"]
• [7.14.5 "inline-progression-dimension"]
• [7.19.3 "keep-together"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.15.4 "line-height"]
• [7.20.2 "overflow"]
• [7.20.3 "reference-orientation"]
• [7.14.12 "width"]
• [7.27.7 "writing-mode"]

6.6.9 fo:leader

Common Usage:

The fo:leader formatting object is often used:

• in table-of-contents to generate sequences of "." glyphs that separate titles from page numbers

• to create entry fields in fill-in-the-blank forms

• to create horizontal rules for use as separators

Areas:

The fo:leader formatting object generates and returns a single normal inline-area.

Trait Derivation:

If the value of the leader-pattern is "use-content" the block-progression-dimension of the content-rectangle is determined in the same manner as for line-areas; otherwise it is determined by the rule-thickness trait.

Constraints:

If the leader's minimum length is too long to place in the line-area, the leader will begin a new line. If it is too long to be placed in a line by itself, it will overflow the line and potentially overflow the reference-area in accordance with that container's overflow trait.

The fo:leader formatting object can have any inline formatting objects and characters as its children, except that fo:leaders may not be nested. Its children are ignored unless the value of the leader-pattern trait is "use-content".

NOTE:

If the value of the leader-pattern trait is "use-content" and the fo:leader has no children, the leader shall be filled with blank space.

The inline-area generated by the fo:leader has a dimension in the inline-progression-direction which shall be at least the leader-length.minimum and at most the leader-length.maximum.

For lines-areas that have been specified to be justified, the justified line-area must honor the leader-alignment trait of any inline-areas generated by fo:leaders.

If the value of the leader-pattern trait is "dots" or "use-content", the following constraint applies:

The inline-area generated by the fo:leader has as its children the areas returned by children of the fo:leader, or obtained by formatting the pattern specified in the leader-pattern trait, repeated an integral number of times. If the width of even a single repetition is larger than the dimension of the inline-area in the inline-progression-direction, the inline-area shall be filled with blank space. The space-start and space-end of the child areas is set to account for the constraints specified in the leader-pattern-width and leader-alignment traits.

NOTE:

If it is desired that the leader should stretch to fill all available space on a line, the maximum length of the leader should be specified to be at least as large as the column width.

NOTE:

The alignment of the leader may be script specific and may require indicating what alignment point is required, because it is different from the default alignment for the script. For example, in some usage of Indic scripts the leader is aligned at the alphabetic baseline.

NOTE:

An fo:leader can be wrapped in an fo:block, yielding a block-area with a line-area containing the leader, to create a rule for separating or decorating block-areas.

Contents:

(#PCDATA|%inline;)*

The content must not contain an fo:leader, fo:inline-container, fo:block-container, fo:float, fo:footnote, or fo:marker either as a direct child or as a descendant.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.8 Common Font Properties]
• [7.11 Common Margin Properties-Inline]
• [7.12 Common Relative Position Properties]
• [7.13.1 "alignment-adjust"]
• [7.13.2 "alignment-baseline"]
• [7.13.3 "baseline-shift"]
• [7.17.1 "color"]
• [7.13.5 "dominant-baseline"]
• [7.27.5 "text-depth"]
• [7.27.4 "text-altitude"]
• [7.28.2 "id"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.21.1 "leader-alignment"]
• [7.21.4 "leader-length"]
• [7.21.2 "leader-pattern"]
• [7.21.3 "leader-pattern-width"]
• [7.21.5 "rule-style"]
• [7.21.6 "rule-thickness"]
• [7.16.2 "letter-spacing"]
• [7.15.4 "line-height"]
• [7.16.5 "text-shadow"]
• [7.28.8 "visibility"]
• [7.16.8 "word-spacing"]

6.6.10 fo:page-number

Common Usage:

The fo:page-number formatting object is used to obtain an inline-area whose content is the page-number for the page on which the inline-area is placed.

Areas:

The fo:page-number formatting object generates and returns a single normal inline-area.

Constraints:

The child areas of this inline-area are the same as the result of formatting a result-tree fragment consisting of fo:character flow objects; one for each character in the page-number string and with only the "character" property specified.

The page-number string is obtained by converting the page-number for the page on which the inline-area is placed in accordance with the number to string conversion properties of the ancestor fo:page-sequence.

NOTE:

The conversion properties are: [7.24.1 "format"], [7.24.2 "grouping-separator"], [7.24.3 "grouping-size"], [7.24.4 "letter-value"], [7.9.1 "country"], and [7.9.2 "language"].

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.8 Common Font Properties]
• [7.11 Common Margin Properties-Inline]
• [7.12 Common Relative Position Properties]
• [7.13.1 "alignment-adjust"]
• [7.13.2 "alignment-baseline"]
• [7.13.3 "baseline-shift"]
• [7.13.5 "dominant-baseline"]
• [7.28.2 "id"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.16.2 "letter-spacing"]
• [7.15.4 "line-height"]
• [7.28.6 "score-spaces"]
• [7.27.4 "text-altitude"]
• [7.16.4 "text-decoration"]
• [7.27.5 "text-depth"]
• [7.16.5 "text-shadow"]
• [7.16.6 "text-transform"]
• [7.28.8 "visibility"]
• [7.16.8 "word-spacing"]
• [7.15.13 "wrap-option"]

6.6.11 fo:page-number-citation

Common Usage:

The fo:page-number-citation is used to reference the page-number for the page containing the first normal area returned by the cited formatting object.

NOTE:

It may be used to provide the page-numbers in the table of contents, cross-references, and index entries.

Areas:

The fo:page-number-citation formatting object generates and returns a single normal inline-area.

Constraints:

The cited page-number is the number of the page containing, as a descendant, the first normal area returned by the formatting object with an id trait matching the ref-id trait of the fo:page-number-citation (the referenced formatting object).

The cited page-number string is obtained by converting the cited page-number in accordance with the number to string conversion properties of the ancestor fo:page-sequence of the referenced formatting object.

NOTE:

The conversion properties are: [7.24.1 "format"], [7.24.2 "grouping-separator"], [7.24.3 "grouping-size"], [7.24.4 "letter-value"], [7.9.1 "country"], and [7.9.2 "language"].

The child areas of the generated inline-area are the same as the result of formatting a result-tree fragment consisting of fo:character flow objects; one for each character in the cited page-number string and with only the "character" property specified.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.8 Common Font Properties]
• [7.11 Common Margin Properties-Inline]
• [7.12 Common Relative Position Properties]
• [7.13.1 "alignment-adjust"]
• [7.13.2 "alignment-baseline"]
• [7.13.3 "baseline-shift"]
• [7.13.5 "dominant-baseline"]
• [7.28.2 "id"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.16.2 "letter-spacing"]
• [7.15.4 "line-height"]
• [7.28.5 "ref-id"]
• [7.28.6 "score-spaces"]
• [7.27.4 "text-altitude"]
• [7.16.4 "text-decoration"]
• [7.27.5 "text-depth"]
• [7.16.5 "text-shadow"]
• [7.16.6 "text-transform"]
• [7.28.8 "visibility"]
• [7.16.8 "word-spacing"]
• [7.15.13 "wrap-option"]

6.7 Formatting Objects for Tables

6.7.1 Introduction

There are nine formatting objects used to construct tables: fo:table-and-caption, fo:table, fo:table-column, fo:table-caption, fo:table-header, fo:table-footer, fo:table-body, fo:table-row, and fo:table-cell. The result tree structure is shown below.

6.7.1.1 Examples

6.7.1.1.1 Simple Table, Centered and Indented

Input sample:

<doc>
<table>
<caption><p>Caption for this table</p></caption>
<tgroup cols="3" width="325pt">
<colspec colwidth="100pt"/>
<colspec colwidth="150pt"/>
<colspec colwidth="75pt"/>
<tbody>
<row>
<entry><p>Cell 1</p></entry>
<entry><p>Cell 2</p></entry>
<entry><p>Cell 3</p></entry>
</row>
</tbody>
</tgroup>
</table>
</doc>

The table and its caption is centered in the available space between the following indents: start-indent="100pt" and end-indent="0pt". The centering and indent is not desired for the content of the caption and the cells.

XSL Stylesheet:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fo="http://www.w3.org/1999/XSL/Format"
                version='1.0'>

<xsl:attribute-set name="inside-table">
  <xsl:attribute name="start-indent">0pt</xsl:attribute>
  <xsl:attribute name="text-align">start</xsl:attribute>
</xsl:attribute-set>

<xsl:template match="p">
  <fo:block>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="table">
  <fo:table-and-caption text-align="center" start-indent="100pt">
    <xsl:apply-templates/>
  </fo:table-and-caption>
</xsl:template>

<xsl:template match="caption">
  <fo:table-caption xsl:use-attribute-sets="inside-table">
    <xsl:apply-templates/>
  </fo:table-caption>
</xsl:template>

<xsl:template match="tgroup">
  <fo:table width="{@width}" table-layout="fixed">
    <xsl:apply-templates/>
  </fo:table>
</xsl:template>

<xsl:template match="colspec">
  <fo:table-column column-width="{@colwidth}">
    <xsl:attribute name="column-number">
      <xsl:number count="colspec"/>
    </xsl:attribute>
  </fo:table-column>
</xsl:template>

<xsl:template match="tbody">
  <fo:table-body xsl:use-attribute-sets="inside-table">
    <xsl:apply-templates/>
  </fo:table-body>
</xsl:template>

<xsl:template match="row">
  <fo:table-row>
    <xsl:apply-templates/>
  </fo:table-row>
</xsl:template>

<xsl:template match="entry">
  <fo:table-cell>
    <xsl:apply-templates/>
  </fo:table-cell>
</xsl:template>

</xsl:stylesheet>

Result Instance: elements and attributes in the fo: namespace

<fo:table-and-caption text-align="center" start-indent="100pt">

  <fo:table-caption start-indent="0pt" text-align="start">
    <fo:block>Caption for this table
    </fo:block>
  </fo:table-caption>

  <fo:table width="325pt" table-layout="fixed">

    <fo:table-column column-width="100pt" column-number="1">
    </fo:table-column>
    <fo:table-column column-width="150pt" column-number="2">
    </fo:table-column>
    <fo:table-column column-width="75pt" column-number="3">
    </fo:table-column>

    <fo:table-body start-indent="0pt" text-align="start">

    <fo:table-row>

    <fo:table-cell>
    <fo:block>Cell 1
    </fo:block>
    </fo:table-cell>
    <fo:table-cell>
    <fo:block>Cell 2
    </fo:block>
    </fo:table-cell>
    <fo:table-cell>
    <fo:block>Cell 3
    </fo:block>
    </fo:table-cell>

    </fo:table-row>

    </fo:table-body>

  </fo:table>

</fo:table-and-caption>

6.7.1.1.2 Simple Table with Relative Column-width Specifications

This example is using a simple, "Oasis-table-model-like", markup for the table elements. The column-widths are specified using full relative column-width specification.

Input sample:

<doc>
<table>
<tgroup cols="3">
<colspec colname="col1" colwidth="1*"/>
<colspec colname="col2" colwidth="2*+2pi"/>
<colspec colname="col3" colwidth="72"/>
<tbody>
<row>
<entry colnum="1" valign="top"><p>Cell 1</p></entry>
<entry colnum="2" valign="middle" align="center"><p>Cell 2</p></entry>
<entry colnum="3" align="center"><p>Cell 3</p></entry>
</row>
</tbody>
</tgroup>
</table>
</doc>

XSL Stylesheet:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fo="http://www.w3.org/1999/XSL/Format"
                version='1.0'>

<xsl:template match="p">
  <fo:block>
    <xsl:apply-templates/>
  </fo:block>
</xsl:template>

<xsl:template match="table">
  <fo:table width="12cm" table-layout="fixed">
    <xsl:apply-templates/>
  </fo:table>
</xsl:template>

<xsl:template match="colspec">
  <fo:table-column>
    <xsl:attribute name="column-number">
      <xsl:number count="colspec"/>
    </xsl:attribute>
    <xsl:attribute name="column-width">
      <xsl:call-template name="calc.column.width">
        <xsl:with-param name="colwidth">
          <xsl:value-of select="@colwidth"/>
        </xsl:with-param>
      </xsl:call-template>
    </xsl:attribute>
  </fo:table-column>
</xsl:template>

<xsl:template match="tbody">
  <fo:table-body>
    <xsl:apply-templates/>
  </fo:table-body>
</xsl:template>

<xsl:template match="row">
  <fo:table-row>
    <xsl:apply-templates/>
  </fo:table-row>
</xsl:template>

<xsl:template match="entry">
  <fo:table-cell column-number="{@colnum}">
    <xsl:if test="@valign">
      <xsl:choose>
        <xsl:when test="@valign='middle'">
          <xsl:attribute name="display-align">center</xsl:attribute>
        </xsl:when>
        <xsl:otherwise>
          <xsl:attribute name="display-align">
            <xsl:value-of select="@valign"/>
          </xsl:attribute>
        </xsl:otherwise>
      </xsl:choose>
    </xsl:if>
    <xsl:if test="@align">
      <xsl:attribute name="text-align">
        <xsl:value-of select="@align"/>
      </xsl:attribute>
    </xsl:if>
    <xsl:apply-templates/>
  </fo:table-cell>
</xsl:template>


<xsl:template name="calc.column.width">
<!-- **
     * <p>Calculate an XSL FO table column-width specification from a
     * full relative table column-width specification.</p>
     *
     * <p>Table column-widths are in the following basic
     * forms:</p>
     *
     * <ul>
     * <li><b>99.99units</b>, a fixed length-specifier.</li>
     * <li><b>99.99</b>, a fixed length-specifier without any units.</li>
     * <li><b>99.99*</b>, a relative length-specifier.</li>
     * <li><b>99.99*+99.99units</b>, a combination of both.</li>
     * </ul>
     *
     * <p>The units are points (pt), picas (pi), centimeters (cm),
     * millimeters (mm), and inches (in). These are the same units as XSL,
     * except that XSL abbreviates picas "pc" instead of "pi". If a length
     * specifier has no units, the default unit (pt) is assumed.</p>
     *
     * <p>Relative length-specifiers are represented in XSL with the
     * proportional-column-width() function.</p>
     *
     * <p>Here are some examples:</p>
     *
     * <ul>
     * <li>"36pt" becomes "36pt"</li>
     * <li>"3pi" becomes "3pc"</li>
     * <li>"36" becomes "36pt"</li>
     * <li>"3*" becomes "proportional-column-width(3)"</li>
     * <li>"3*+2pi" becomes "proportional-column-width(3)+2pc"</li>
     * <li>"1*+2" becomes "proportional-column-width(1)+2pt"</li>
     * </ul>
     *
     * @param colwidth The column width specification.
     *
     * @returns The XSL column width specification.
     * -->
  <xsl:param name="colwidth">1*</xsl:param>

  <!-- Ok, the colwidth could have any one of the following forms: -->
  <!--        1*       = proportional width -->
  <!--     1unit       = 1.0 units wide -->
  <!--         1       = 1pt wide -->
  <!--  1*+1unit       = proportional width + some fixed width -->
  <!--      1*+1       = proportional width + some fixed width -->

  <!-- If it has a proportional width, translate it to XSL -->
  <xsl:if test="contains($colwidth, '*')">
    <xsl:text>proportional-column-width(</xsl:text>
    <xsl:value-of select="substring-before($colwidth, '*')"/>
    <xsl:text>)</xsl:text>
  </xsl:if>

  <!-- Now get the non-proportional part of the specification -->
  <xsl:variable name="width-units">
    <xsl:choose>
      <xsl:when test="contains($colwidth, '*')">
        <xsl:value-of
             select="normalize-space(substring-after($colwidth, '*'))"/>
      </xsl:when>
      <xsl:otherwise>
        <xsl:value-of select="normalize-space($colwidth)"/>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:variable>

  <!-- Now the width-units could have any one of the following forms: -->
  <!--                 = <empty string> -->
  <!--     1unit       = 1.0 units wide -->
  <!--         1       = 1pt wide -->
  <!-- with an optional leading sign -->

  <!-- Get the width part by blanking out the units part and discarding -->
  <!-- white space. -->
  <xsl:variable name="width"
       select="normalize-space(translate($width-units,
                                         '+-0123456789.abcdefghijklmnopqrstuvwxyz',
                                         '+-0123456789.'))"/>

  <!-- Get the units part by blanking out the width part and discarding -->
  <!-- white space. -->
  <xsl:variable name="units"
       select="normalize-space(translate($width-units,
                                         'abcdefghijklmnopqrstuvwxyz+-0123456789.',
                                         'abcdefghijklmnopqrstuvwxyz'))"/>

  <!-- Output the width -->
  <xsl:value-of select="$width"/>

  <!-- Output the units, translated appropriately -->
  <xsl:choose>
    <xsl:when test="$units = 'pi'">pc</xsl:when>
    <xsl:when test="$units = '' and $width != ''">pt</xsl:when>
    <xsl:otherwise><xsl:value-of select="$units"/></xsl:otherwise>
  </xsl:choose>
</xsl:template>

</xsl:stylesheet>

Result Instance: elements and attributes in the fo: namespace

<fo:table width="12cm" table-layout="fixed">
  <fo:table-column column-number="1" column-width="proportional-column-width(1)">
  </fo:table-column>
  <fo:table-column column-number="2" column-width="proportional-column-width(2)+2pc">
  </fo:table-column>
  <fo:table-column column-number="3" column-width="72pt">
  </fo:table-column>
  <fo:table-body>
    <fo:table-row>
      <fo:table-cell column-number="1" display-align="top">
        <fo:block>Cell 1
        </fo:block>
      </fo:table-cell>
      <fo:table-cell column-number="2" display-align="center" text-align="center">
        <fo:block>Cell 2
        </fo:block>
      </fo:table-cell>
      <fo:table-cell column-number="3" text-align="center">
        <fo:block>Cell 3
        </fo:block>
      </fo:table-cell>
    </fo:table-row>
  </fo:table-body>
</fo:table>

6.7.2 fo:table-and-caption

Common Usage:

The fo:table-and-caption flow object is used for formatting a table together with its caption.

NOTE:

A fo:table-and-caption may be placed inline by enclosing it in an fo:inline-container.

NOTE:

This formatting object corresponds to the CSS anonymous box that encloses the table caption and the table.

Areas:

The fo:table-and-caption formatting object generates one or more normal block-areas. The fo:table-and-caption returns these areas, any page-level-out-of-line areas, and any reference-level-out-of-line areas returned by the children of the fo:table-and-caption.

Constraints:

No area may have more than one normal child area returned by the same fo:table-and-caption formatting object.

The children of the areas generated by the fo:table-and-caption are one or two areas; one for the table caption and one for the table itself. These are positioned relative to each other as specified by the caption-side trait. They are placed relative to the content-rectangle of the generated area as specified by the text-align trait.

Contents:

(table-caption?,table)

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.10 Common Margin Properties-Block]
• [7.12 Common Relative Position Properties]
• [7.19.1 "break-after"]
• [7.19.2 "break-before"]
• [7.26.7 "caption-side"]
• [7.28.2 "id"]
• [7.18.3 "intrusion-displace"]
• [7.19.3 "keep-together"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.15.9 "text-align"]

6.7.3 fo:table

Common Usage:

The fo:table flow object is used for formatting the tabular material of a table.

The fo:table flow object and its child flow objects model the visual layout of a table in a "row primary" manner. A complete table may be seen as consisting of a grid of rows and columns where each cell occupies one or more grid units in the row-progression-direction and column-progression-direction.

The table content is divided into a header (optional), footer (optional), and one or more bodies. Properties specify if the headers and footers should be repeated at a break in the table. Each of these parts occupies one or more rows in the table grid.

Areas:

The fo:table formatting object generates and returns one or more normal block-areas. In addition the fo:table returns any page-level-out-of-line areas, and any reference-level-out-of-line areas returned by the children of the fo:table.

The areas generated and returned by the fo:table formatting object have as children:

• Areas, with only background, corresponding to the table-header, table-footer, table-body, spanned columns, columns, and rows.

  NOTE:

  The spanned columns (fo:table-column with a "number-columns-spanned" value greater than 1) are used in the same way as the "column groups" in CSS2 for determining the background.

• Areas returned by the fo:table-cell formatting objects.

These areas have a z-index controlling the rendering order determined in accordance with 17.5.1 of the CSS2 specification (http://www.w3.org/TR/REC-CSS2/tables.html#table-layers").

NOTE:

A cell that is spanned may have a different background in each of the grid units it occupies.

Trait Derivation:

The areas generated and returned by the fo:table formatting object have a value of "true" for the is-reference-area.

The column-progression-direction and row-progression-direction are determined by the writing-mode trait. Columns use the inline-progression-direction, and rows use the block-progression-direction.

The method for deriving the border traits for a table is specified by the "border-collapse" property.

If the value of the "border-collapse" property is "separate" the border is composed of two components. The first, which is placed with the inside edge coincident with the outermost table grid boundary line, has the width of half the value for the "border-separation" property. It is filled in accordance with the "background" property of the fo:table. Second, outside the outermost table grid boundary line is placed, for each side of the table, a border based on a border specified on the table.

If the value of the "border-collapse" property is "collapse" or "collapse-with-precedence" the border is determined, for each segment, at the cell level.

NOTE:

By specifying "collapse-with-precedence" and an appropriately high precedence on the border specification for the fo:table one may ensure that this specification is the one used on all border segments.

Constraints:

No area may have more than one normal child area returned by the same fo:table formatting object.

The inline-progression-dimension of the content-rectangle of the table is the sum of the inline-progression-dimensions of the columns in the table grid. The method used to determine these inline-progression-dimensions is governed by the values of the table-layout and the inline-progression-dimension traits in the following manner:

inline-progression-dimension="auto" table-layout="auto"

The automatic table layout shall be used.

inline-progression-dimension="auto" table-layout="fixed"

The automatic table layout shall be used.

inline-progression-dimension=<length> or <percentage> table-layout="auto"

The automatic table layout shall be used.

inline-progression-dimension=<length> or <percentage> table-layout="fixed"

The fixed table layout shall be used.

The automatic table layout and fixed table layout is defined in 17.5.2 of the CSS2 specification (http://www.w3.org/TR/REC-CSS2/tables.html#width-layout").

The method for determining the block-progression-dimension of the table is governed by the block-progression-dimension trait.

NOTE:

The CSS2 specification explicitly does not specify what the behavior should be if there is a mismatch between an explicitly specified table block-progression-dimension and the block-progression-dimensions of the content.

NOTE:

The use of the "proportional-column-width()" function is only permitted when the fixed table layout is used.

If the use of proportional column widths are desired on a table of an unknown explicit width, the inline-progression-dimension cannot be specified to be "auto". Instead, the width must be specified as a percentage. For example, setting table-layout="fixed" and inline-progression-dimension="100%" would allow proportional column widths while simultaneously creating a table as wide as possible in the current context.

NOTE:

The result of using a percentage for the width may be unpredictable, especially when using the automatic table layout.

It is an error if two table-cells overlap.

NOTE:

Such overlap could be due to the same column-number being assigned to two different cells in the same row, or due to column or row spanning causing an overlap.

Contents:

(table-column*,table-header?,table-footer?,table-body+)

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.10 Common Margin Properties-Block]
• [7.12 Common Relative Position Properties]
• [7.14.1 "block-progression-dimension"]
• [7.26.1 "border-after-precedence"]
• [7.26.2 "border-before-precedence"]
• [7.26.3 "border-collapse"]
• [7.26.4 "border-end-precedence"]
• [7.26.5 "border-separation"]
• [7.26.6 "border-start-precedence"]
• [7.19.1 "break-after"]
• [7.19.2 "break-before"]
• [7.28.2 "id"]
• [7.14.5 "inline-progression-dimension"]
• [7.18.3 "intrusion-displace"]
• [7.14.4 "height"]
• [7.19.3 "keep-together"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]
• [7.26.16 "table-layout"]
• [7.26.17 "table-omit-footer-at-break"]
• [7.26.18 "table-omit-header-at-break"]
• [7.14.12 "width"]
• [7.27.7 "writing-mode"]

6.7.4 fo:table-column

Common Usage:

The fo:table-column auxiliary formatting object specifies characteristics applicable to table cells that have the same column and span. The most important property is the "column-width" property.

Areas:

The fo:table-column formatting object does not generate or return any areas. It holds a set of traits that provide constraints on the column widths and a specification of some presentation characteristics, such as background which affects the areas generated by the fo:table (see [6.7.3 fo:table]). Inheritable properties may also be specified on the fo:table-column. These can be referenced by the from-table-column() function in an expression.

Constraints:

None.

Contents:

EMPTY

The following properties apply to this formatting object:

• [7.7 Common Border, Padding, and Background Properties]

  NOTE:

  Only the background properties from this set apply. If the value of border-collapse is "collapse" or "collapse-with-precedence" for the table the border properties also apply.

• [7.26.8 "column-number"]
• [7.26.9 "column-width"]
• [7.26.12 "number-columns-repeated"]
• [7.26.13 "number-columns-spanned"]
• [7.28.8 "visibility"]

6.7.5 fo:table-caption

Common Usage:

The fo:table-caption formatting object is used to contain block-level formatting objects containing the caption for the table only when using the fo:table-and-caption.

Areas:

The fo:table-caption formatting object generates one or more normal reference-areas. The fo:table-caption returns these reference-areas and any page-level-out-of-line areas returned by the children of the fo:table-caption.

Trait Derivation:

The areas generated by the fo:table-caption formatting object have a value of "true" for the is-reference-area.

Constraints:

For the case when the value of the caption-side trait is "before" or "after" the inline-progression-dimension of the content-rectangle of the generated reference-area is equal to the inline-progression-dimension of the content-rectangle of the reference-area that encloses it.

When the value is "start" or "end" the inline-progression-dimension of the generated reference-area is constrained by the value of the inline-progression-dimension trait.

When the value is "top", "bottom", "left", or "right" the value is mapped in the same way as for corresponding properties (see [5.3 Computing the Values of Corresponding Properties]) and the property is then treated as if the corresponding value had been specified.

If the caption is to be positioned before the table, the areas generated by the fo:table-caption shall be placed in the area tree as though the fo:table-caption had a "keep-with-next" property with value "always".

If the caption is to be positioned after the table, the areas generated by the fo:table-caption shall be placed in the area tree as though the fo:table-caption had a "keep-with-previous" property with value "always".

No area may have more than one normal child area returned by the same fo:table-caption formatting object.

The children of each normal area returned by an fo:table-caption formatting object must be normal block-areas returned by the children of the fo:table-caption, must be properly stacked, and must be properly ordered.

Any reference-level-out-of-line areas returned by the children of the fo:table-caption are handled as described in [6.10.2 fo:float].

Contents:

(%block;)+

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.12 Common Relative Position Properties]
• [7.14.1 "block-progression-dimension"]
• [7.14.4 "height"]
• [7.28.2 "id"]
• [7.14.5 "inline-progression-dimension"]
• [7.18.3 "intrusion-displace"]
• [7.19.3 "keep-together"]
• [7.14.12 "width"]

6.7.6 fo:table-header

Common Usage:

The fo:table-header formatting object is used to contain the content of the table header.

Areas:

The fo:table-header formatting object does not generate any areas. The fo:table-header formatting object returns the sequence of areas created by concatenating the sequences of areas returned by each of the children of the fo:table-header.

Constraints:

The order of concatenation of the sequences of areas returned by the children of the fo:table-header is the same order as the children are ordered under the fo:table-header.

Contents:

(table-row+|table-cell+)

The fo:table-header has fo:table-row (one or more) as its children, or alternatively fo:table-cell (one or more). In the latter case cells are grouped into rows using the starts-row and ends-row properties.

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]

  NOTE:

  Only the background properties from this set apply. If the value of border-collapse is "collapse" or "collapse-with-precedence" for the table the border properties also apply.

• [7.12 Common Relative Position Properties]
• [7.26.1 "border-after-precedence"]
• [7.26.2 "border-before-precedence"]
• [7.26.4 "border-end-precedence"]
• [7.26.6 "border-start-precedence"]
• [7.28.2 "id"]

6.7.7 fo:table-footer

Common Usage:

The fo:table-footer formatting object is used to contain the content of the table footer.

Areas:

The fo:table-footer formatting object does not generate any areas. The fo:table-footer formatting object returns the sequence of areas created by concatenating the sequences of areas returned by each of the children of the fo:table-footer.

Constraints:

The order of concatenation of the sequences of areas returned by the children of the fo:table-footer is the same order as the children are ordered under the fo:table-footer.

Contents:

(table-row+|table-cell+)

The fo:table-footer has fo:table-row (one or more) as its children, or alternatively fo:table-cell (one or more). In the latter case cells are grouped into rows using the starts-row and ends-row properties.

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]

  NOTE:

  Only the background properties from this set apply. If the value of border-collapse is "collapse" or "collapse-with-precedence" for the table the border properties also apply.

• [7.12 Common Relative Position Properties]
• [7.26.1 "border-after-precedence"]
• [7.26.2 "border-before-precedence"]
• [7.26.4 "border-end-precedence"]
• [7.26.6 "border-start-precedence"]
• [7.28.2 "id"]

6.7.8 fo:table-body

Common Usage:

The fo:table-body formatting object is used to contain the content of the table body.

Areas:

The fo:table-body formatting object does not generate any areas. The fo:table-body formatting object returns the sequence of areas created by concatenating the sequences of areas returned by each of the children of the fo:table-body.

Constraints:

The order of concatenation of the sequences of areas returned by the children of the fo:table-body is the same order as the children are ordered under the fo:table-body.

Contents:

(table-row+|table-cell+)

The fo:table-body has fo:table-row (one or more) as its children, or alternatively fo:table-cell (one or more). In the latter case cells are grouped into rows using the starts-row and ends-row properties.

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]

  NOTE:

  Only the background properties from this set apply. If the value of border-collapse is "collapse" or "collapse-with-precedence" for the table the border properties also apply.

• [7.12 Common Relative Position Properties]
• [7.26.1 "border-after-precedence"]
• [7.26.2 "border-before-precedence"]
• [7.26.4 "border-end-precedence"]
• [7.26.6 "border-start-precedence"]
• [7.28.2 "id"]

6.7.9 fo:table-row

Common Usage:

The fo:table-row formatting object is used to group table-cells into rows; all table-cells in a table-row start in the same geometric row on the table grid.

Areas:

The fo:table-row formatting object does not generate any areas. The fo:table-row formatting object returns the sequence of areas created by concatenating the sequences of areas returned by each of the children of the fo:table-row. The fo:table-row holds a specification of some presentation characteristics, such as background which affects the areas generated by the fo:table (see [6.7.3 fo:table]).

Constraints:

The order of concatenation of the sequences of areas returned by the children of the fo:table-row is the same order as the children are ordered under the fo:table-row.

The method for determining the height of the row in the grid is governed by the row-height trait.

Contents:

(table-cell+)

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.14.1 "block-progression-dimension"]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]

  NOTE:

  Only the background properties from this set apply. If the value of border-collapse is "collapse" or "collapse-with-precedence" for the table the border properties also apply.

• [7.12 Common Relative Position Properties]
• [7.26.1 "border-after-precedence"]
• [7.26.2 "border-before-precedence"]
• [7.26.4 "border-end-precedence"]
• [7.26.6 "border-start-precedence"]
• [7.19.1 "break-after"]
• [7.19.2 "break-before"]
• [7.28.2 "id"]
• [7.14.4 "height"]
• [7.19.3 "keep-together"]
• [7.19.4 "keep-with-next"]
• [7.19.5 "keep-with-previous"]

6.7.10 fo:table-cell

Common Usage:

The fo:table-cell formatting object is used to group content to be placed in a table cell.

The "starts-row" and "ends-row" properties can be used when the input data does not have elements containing the cells in each row, but instead, for example, each row starts at elements of a particular type.

Areas:

The fo:table-cell formatting object generates one or more normal reference-areas. The fo:table-cell returns these reference-areas and any page-level-out-of-line areas returned by the children of the fo:table-cell.

Trait Derivation:

The areas generated by the fo:table-cell formatting object have a value of "true" for the is-reference-area.

The method for deriving the border for a cell is specified by the border-collapse trait.

If the value of the border-collapse trait is "separate" the border is composed of two components. The first, which is placed with the outside edge coincident with the table grid boundary line, has the width of half the value for the border-separation trait. It is filled in accordance with the background trait of the fo:table. Inside this border is placed, for each side of the cell, a border based on a border specified on the cell or inherited.

If the value of the border-collapse trait is "collapse-with-precedence" the border for each side of the cell is determined by, for each segment of a border, selecting, from all border specifications for that segment, the border that has the highest precedence. It is an error if there are two such borders that have the same precedence but are not identical. Each border segment is placed centered on the table grid boundary line. On devices that do not support sub-pixel rendering, if an effective border width is determined to be an odd number of pixels it is implementation defined on which side of the grid boundry line the odd pixel is placed.

If the value of the border-collapse trait is "collapse", the border for each side of the cell is determined by, for each segment of a border, selecting, from all border specifications for that segment, the border that has the most "eye catching" border style, see below for the details. Each border segment is placed centered on the table grid boundary line. On devices that do not support sub-pixel rendering, if an effective border width is determined to be an odd number of pixels it is implementation defined on which side of the grid boundary line the odd pixel is placed. Where there is a conflict between the styles of border segments that collapse, the following rules determine which border style "wins":

1. Borders with the 'border-style' of 'hidden' take precedence over all other conflicting borders. Any border with this value suppresses all borders at this location.

2. Borders with a style of 'none' have the lowest priority. Only if the border properties of all the elements meeting at this edge are 'none' will the border be omitted (but note that 'none' is the default value for the border style.)

3. If none of the styles is 'hidden' and at least one of them is not 'none', then narrow borders are discarded in favor of wider ones.

4. If the remaining border styles have the same 'border-width' than styles are preferred in this order: 'double', 'solid', 'dashed', 'dotted', 'ridge', 'outset', 'groove', and the lowest: 'inset'.

5. If border styles differ only in color, then a style set on a cell wins over one on a row, which wins over a row group, column, column group and, lastly, table.

Constraints:

A table-cell occupies one or more grid units in the row-progression-direction and column-progression-direction. The content-rectangle of the cell is the size of the portion of the grid the cell occupies minus, for each of the four sides:

• If the value of the border-collapse trait is "separate": half the value of the border-separation trait; otherwise 0.

• If the value of the border-collapse trait is "separate": the thickness of the cell-border; otherwise half the thickness of the effective border.

• The cell padding.

The method for determining the block-progression-dimension of the cell in the grid is governed by the row-height trait.

No area may have more than one normal child area returned by the same fo:table-cell formatting object.

The children of each normal area returned by an fo:table-cell formatting object must be normal block-areas returned by the children of the fo:table-cell, must be properly stacked, and must be properly ordered.

Any reference-level-out-of-line areas returned by the children of the fo:table-cell are handled as described in [6.10.2 fo:float].

Contents:

(%block;)+

In addition this formatting object may have a sequence of zero or more fo:markers as its initial children.

The following properties apply to this formatting object:

• [7.4 Common Accessibility Properties]
• [7.6 Common Aural Properties]
• [7.7 Common Border, Padding, and Background Properties]
• [7.12 Common Relative Position Properties]
• [7.26.1 "border-after-precedence"]
• [7.26.2 "border-before-precedence"]
• [7.26.4 "border-end-precedence"]
• [7.26.6 "border-start-precedence"]
• [7.14.1 "block-progression-dimension"]
• [7.26.8 "column-number"]
• [7.13.4 "display-align"]
• [7.13.6 "relative-align"]
• [7.26.10 "empty-cells"]
• [7.26.11 "ends-row"]
• [7.14.4 "height"]
• [7.28.2 "id"]
• [7.26.13 "number-columns-spanned"]
• [7.26.14 "number-rows-spanned"]
• [7.26.15 "starts-row"]
• [7.14.12 "width"]

6.8 Formatting Objects for Lists

6.8.1 Introduction

There are four formatting objects used to construct lists: fo:list-block, fo:list-item, fo:list-item-label, and fo:list-item-body.

The fo:list-block has the role of containing the complete list and of specifying values used for the list geometry in the inline-progression-direction (see details below).

The children of the fo:list-block are one or more fo:list-item, each containing a pair of fo:list-item-label and fo:list-item-body.

The fo:list-item has the role of containing each item in a list.

The fo:list-item-label has the role of containing the content, block-level formatting objects, of the label for the list-item; typically an fo:block containing a number, a dingbat character, or a term.

The fo:list-item-body has the role of containing the content, block-level formatting objects, of the body of the list-item; typically one or more fo:block.

The placement, in the block-progression-direction, of the label with respect to the body is made in accordance with the "vertical-align" property of the fo:list-item.

The specification of the list geometry in the inline-progression-direction is achieved by:

• Specifying appropriate values of the "provisional-distance-between-starts" and "provisional-label-separation" properties. The "provisional-distance-between-starts" specifies the desired distance between the start-indents of the label and the body of the list-item. The "provisional-label-separation" specifies the desired separation between the end-indent of the label and the start-indent of the body of the list-item.

• Specifying end-indent="label-end()" on the fo:list-item-label.

  Specifying start-indent="body-start()" on the fo:list-item-body.

  NOTE:

  These list specific functions are defined in [7.28.3 "provisional-label-separation"] and [7.28.4 "provisional-distance-between-starts"].