XtCreateWidget(3Xt) X11R5 XtCreateWidget(3Xt)NAME
XtCreateWidget, XtCreateManagedWidget, XtDestroyWidget - create and
destroy widgets
SYNTAX
Widget XtCreateWidget(name, widget_class, parent, args, num_args)
String name;
WidgetClass widget_class;
Widget parent;
ArgList args;
Cardinal num_args;
Widget XtCreateManagedWidget(name, widget_class, parent, args,
num_args)
String name;
WidgetClass widget_class;
Widget parent;
ArgList args;
Cardinal num_args;
void XtDestroyWidget(w)
Widget w;
ARGUMENTS
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.
widget_class
Specifies the widget class pointer for the created widget.
DESCRIPTION
The function performs much of the boilerplate operations of widget cre‐
ation:
· 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 order.
· Allocates memory for the widget instance.
· If the parent is a subclass of it allocates memory for the par‐
ent's constraints and stores the address of this memory into the
constraints field.
· Initializes the core nonresource data fields (for example, parent
and visible).
· Initializes the resource fields (for example, background_pixel) by
using the resource lists specified for this class and all super‐
classes.
· 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
· Calls the initialize procedures for the widget by starting at the
initialize procedure on down to the widget's initialize procedure.
· If the parent is a subclass of it puts the widget into its par‐
ent's children list by calling its parent's insert_child proce‐
dure. For further information, see Section 3.5.
· If the parent is a subclass of it calls the constraint initialize
procedures, starting at on down to the parent's constraint ini‐
tialize procedure.
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:
· If the being_destroyed field of the widget is it returns immedi‐
ately.
· Recursively descends the widget tree and sets the being_destroyed
field to 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 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 registered
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:
· 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 and if the parent is not
being destroyed, it calls on the widget and then calls the wid‐
get's parent's delete_child procedure (see Section 3.4).
· 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
· 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.
· Calls 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 sub‐
class of children.
SEE ALSOXtAppCreateShell(3Xt), XtCreatePopupShell(3Xt)
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface
XtCreateWidget(3Xt)