Specifies the widget class pointer
for the created widget. ...Specifies the variable argument list to override
the resource defaults.
The XtCreateWidget function performs
much of the boilerplate operations of widget creation:
- Checks to see if
the class_initialize procedure has been called for this class and for all
superclasses and, if not, calls those necessary in a superclass-to-subclass
- Allocates memory for the widget instance.
- If the parent is a subclass
of constraintWidgetClass, it allocates memory for the parent's constraints
and stores the address of this memory into the constraints field.
the core nonresource data fields (for example, parent and visible).
the resource fields (for example, background_pixel) by using the resource
lists specified for this class and all superclasses.
- If the parent is a
subclass of constraintWidgetClass, it initializes the resource fields
of the constraints record by using the constraint resource list specified
for the parent's class and all superclasses up to constraintWidgetClass.
- Calls the initialize procedures for the widget by starting at the Core
initialize procedure on down to the widget's initialize procedure.
- If the
parent is a subclass of compositeWidgetClass, it puts the widget into
its parent's children list by calling its parent's insert_child procedure.
For further information, see Section 3.5.
- If the parent is a subclass of
constraintWidgetClass, it calls the constraint initialize procedures,
starting at constraintWidgetClass on down to the parent's constraint initialize
Note that you can determine the number of arguments in an argument
list by using the XtNumber macro. For further information, see Section
The XtCreateManagedWidget function is a convenience routine that
calls XtCreateWidget and XtManageChild.
The XtDestroyWidget function
provides the only method of destroying a widget, including widgets that
need to destroy themselves. It can be called at any time, including from
an application callback routine of the widget being destroyed. This requires
a two-phase destroy process in order to avoid dangling references to destroyed
In phase one, XtDestroyWidget performs the following:
- If the
being_destroyed field of the widget is True, it returns immediately.
- Recursively descends the widget tree and sets the being_destroyed field
to True for the widget and all children.
- Adds the widget to a list of
widgets (the destroy list) that should be destroyed when it is safe to
Entries on the destroy list satisfy the invariant that if w2 occurs
after w1 on the destroy list then w2 is not a descendent of w1. (A descendant
refers to both normal and pop-up children.)
Phase two occurs when all procedures
that should execute as a result of the current event have been called (including
all procedures registered with the event and translation managers), that
is, when the current invocation of XtDispatchEvent is about to return
or immediately if not in XtDispatchEvent.
In phase two, XtDestroyWidget
performs the following on each entry in the destroy list:
- Calls the destroy
callback procedures registered on the widget (and all descendants) in
post-order (it calls children callbacks before parent callbacks).
- If the
widget's parent is a subclass of compositeWidgetClass and if the parent
is not being destroyed, it calls XtUnmanageChild on the widget and
then calls the widget's parent's delete_child procedure (see Section 3.4).
- If the widget's parent is a subclass of constraintWidgetClass, it calls
the constraint destroy procedure for the parent, then the parent's superclass,
until finally it calls the constraint destroy procedure for constraintWidgetClass.
- Calls the destroy methods for the widget (and all descendants) in post-order.
For each such widget, it calls the destroy procedure declared in the widget
class, then the destroy procedure declared in its superclass, until finally
it calls the destroy procedure declared in the Core class record.
XDestroyWindow if the widget is realized (that is, has an X window). The
server recursively destroys all descendant windows.
- Recursively descends
the tree and deallocates all pop-up widgets, constraint records, callback
lists and, if the widget is a subclass of compositeWidgetClass, children.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface
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