XtCreateWidget(3Xt) MIT X11R4 XtCreateWidget(3Xt)
XtCreateWidget, XtCreateManagedWidget, XtDestroyWidget - create and destroy widgets
Widget XtCreateWidget(name, widget_class, parent, args, num_args)
Widget XtCreateManagedWidget(name, widget_class, parent, args, num_args)
args Specifies the argument list to override the resource defaults.
name Specifies the resource name for the created widget, which is used for retrieving resources and, for that reason, should not be
the same as any other widget that is a child of same parent.
num_args Specifies the number of arguments in the argument list.
parent Specifies the parent widget.
w Specifies the widget.
Specifies the widget class pointer for the created widget.
The function performs much of the boilerplate operations of widget creation:
o Checks to see if the class_initialize procedure has been called for this class and for all superclasses and, if not, calls those nec-
essary in a superclass-to-subclass order.
o Allocates memory for the widget instance.
o If the parent is a subclass of it allocates memory for the parent's constraints and stores the address of this memory into the con-
o Initializes the core nonresource data fields (for example, parent and visible).
o Initializes the resource fields (for example, background_pixel) by using the resource lists specified for this class and all super-
o If the parent is a subclass of 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
o Calls the initialize procedures for the widget by starting at the initialize procedure on down to the widget's initialize procedure.
o If the parent is a subclass of 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.
o If the parent is a subclass of it calls the constraint initialize procedures, starting at on down to the parent's constraint initial-
Note that you can determine the number of arguments in an argument list by using the macro. For further information, see Section 11.1.
The function is a convenience routine that calls and
The 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 widgets.
In phase one, performs the following:
o If the being_destroyed field of the widget is it returns immediately.
o Recursively descends the widget tree and sets the being_destroyed field to for the widget and all children.
o Adds the widget to a list of widgets (the destroy list) that should be destroyed when it is safe to do so.
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 regis-
tered with the event and translation managers), that is, when the current invocation of is about to return or immediately if not in
In phase two, performs the following on each entry in the destroy list:
o Calls the destroy callback procedures registered on the widget (and all descendants) in post-order (it calls children callbacks before
o If the widget's parent is a subclass of and if the parent is not being destroyed, it calls on the widget and then calls the widget's
parent's delete_child procedure (see Section 3.4).
o If the widget's parent is a subclass of it calls the constraint destroy procedure for the parent, then the parent's superclass, until
finally it calls the constraint destroy procedure for
o 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.
o Calls if the widget is realized (that is, has an X window). The server recursively destroys all descendant windows.
o Recursively descends the tree and deallocates all pop-up widgets, constraint records, callback lists and, if the widget is a subclass
X Window System Toolkit: The Complete Programmer's Guide and Specification, Paul J. Asente and Ralph Swick
X Window System: The Complete Reference, Second Edition, Robert W. Scheifler and James Gettys