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 XtCreateWidget 3Xt "Release 3" "X Version 11" "XT FUNCTIONS"
 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 1i
Specifies the argument list \*(Al.
 name 1i
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 1i
Specifies the number of arguments in the argument list.
 parent 1i
Specifies the parent widget.
 w 1i
Specifies the widget.
 widget_class 1i
Specifies the widget class\*(Wc.
 DESCRIPTION
The
.ZN XtCreateWidget
function performs much of the boilerplate operations of widget creation:
 \(bu 5
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.
 \(bu 5
Allocates memory for the widget instance.
 \(bu 5
If the parent is a subclass of
.ZN constraintWidgetClass ,
it allocates memory for the parent's constraints
and stores the address of this memory into the constraints field.
 \(bu 5
Initializes the core nonresource data fields
(for example, parent and visible).
 \(bu 5
Initializes the resource fields (for example, background_pixel)
by using the resource lists specified for this class and all superclasses.
 \(bu 5
If the parent is a subclass of
.ZN 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
.ZN constraintWidgetClass .
 \(bu 5
Calls the initialize procedures for the widget by starting at the 
.ZN Core
initialize procedure on down to the widget's initialize procedure.
 \(bu 5
If the parent is a subclass of
.ZN 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.
 \(bu 5
If the parent is a subclass of
.ZN constraintWidgetClass ,
it calls the constraint initialize procedures,
starting at
.ZN constraintWidgetClass
on down to the parent's constraint initialize procedure.

Note that you can determine the number of arguments in an argument list 
by using the
.ZN XtNumber
macro.
For further information, see Section 11.1.

The
.ZN XtCreateManagedWidget
function is a convenience routine that calls
.ZN XtCreateWidget
and
.ZN XtManageChild .

The
.ZN 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 widgets.

In phase one,
.ZN XtDestroyWidget
performs the following:
 \(bu 5
If the being_destroyed field of the widget is 
.ZN True ,
it returns immediately.
 \(bu 5
Recursively descends the widget tree and
sets the being_destroyed field to 
.ZN True 
for the widget and all children.
 \(bu 5
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
.ZN XtDispatchEvent
is about to return or immediately if not in
.ZN XtDispatchEvent .

In phase two,
.ZN XtDestroyWidget
performs the following on each entry in the destroy list:
 \(bu 5
Calls the destroy callback procedures registered on the widget 
(and all descendants) in post-order (it calls children callbacks 
before parent callbacks).
 \(bu 5
If the widget's parent is a subclass of 
.ZN compositeWidgetClass 
and if the parent is not being destroyed, 
it calls 
.ZN XtUnmanageChild 
on the widget and then calls the widget's parent's delete_child procedure
(see Section 3.4).
 \(bu 5
If the widget's parent is a subclass of
.ZN constraintWidgetClass ,
it calls the constraint destroy procedure for the parent,
then the parent's superclass,
until finally it calls the constraint destroy procedure for
.ZN constraintWidgetClass .
 \(bu 5
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.
 \(bu 5
Calls
.ZN XDestroyWindow
if the widget is realized (that is, has an X window).
The server recursively destroys all descendant windows.
 \(bu 5
Recursively descends the tree and deallocates all pop-up widgets, constraint
records, callback lists and, if the widget is a subclass of 
.ZN compositeWidgetClass , 
children.
 "SEE ALSO"
XtAppCreateShell(3Xt),
XtCreatePopupShell(3Xt)

\*(xT

\*(xL