File 'gui/watchaman.cls' (part of 'Pool_GuiBase')


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Written by
Andreas Kupries
Description
management for option -variable of a widget displaying an array. Actually a stripped down version of valueManager.
Keywords
value management, -value, widgets

Class 'watchAManager'

Description
Defines and manages the option '-variable'. Derived classes must provide the methods 'initDisplay', 'updateDisplay' and 'clearDisplay'. They have to refresh the shown information according to the changed value.
Superclasses
widget
Options
variable
Membervariables
item, operation
Methods
InitializeManager, TrackVarContents, TrackVariable, initDisplay, updateDisplay, watchAManager, ~watchAManager

-variable
Name of the (global) variable associated to the widget. Any changes to its contents are propagated into the widget and vice versa.

item
The key used by the last operation on the array we are connected to, as given by the trace callback (TrackVarContents).
operation
The last operation on the array we are connected to, as given by the trace callback (TrackVarContents).

InitializeManager ()

Special method, is called after the completion of the construction of widget and its components. Initializes the value of the widget according to the contents of the associated variable, if defined.

TrackVarContents (var idx op)

Internal trace callback to monitor the value of the array variable associated to the widget.
Argument: varStandard trace argument, base name of traced variable
Argument: idxStandard trace argument, name of array item.
Argument: opStandard trace argument, operation invoking the trace.

TrackVariable (o oldValue)

Configure procedure. Used to track changes to the value of -variable. Removes the traces set upon the old associated variable, then links in the new variable and its contents.
Argument: oThe name of the changed option.
Argument: oldValueThe value of the option before the change.

initDisplay ()

Dummy method, must be overridden by derived classes. This one will only throw an error.

updateDisplay ()

Dummy method, must be overridden by derived classes. This one will only throw an error.

watchAManager ()

Special constructor. Schedules the execution of the real initialization to happen after the standard initialization and the creation of all component widgets of the derived class.

~watchAManager ()

Special destructor. Removes the association between the widget and the variable specified in '-variable', if the latter is not empty. This is accomplished through the deletion of the variable trace set earlier by this widget.


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