XtCreateWidget, XtVaCreateWidget, XtCreateManagedWidget,
XtVaCreateManagedWidget, XtDestroyWidget - create and destroy widgets
#include <X11/Intrinsic.h>
Widget XtCreateWidget(const char *name, WidgetClass
widget_class, Widget parent, ArgList args, Cardinal
num_args);
Widget XtVaCreateWidget(const char *name, WidgetClass
widget_class, Widget parent, ...);
Widget XtCreateManagedWidget(const char *name,
WidgetClass widget_class, Widget parent, ArgList args,
Cardinal num_args);
Widget XtVaCreateManagedWidget(const char *name,
WidgetClass widget_class, Widget parent, ...);
void XtDestroyWidget(Widget w);
- 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.
- ...
- 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 order.
- 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.
- 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 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 procedure.
Note that you can determine the number of arguments in an argument
list by using the XtNumber macro. For further information, see
Section 11.1.
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 widgets.
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 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 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.
- Calls 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.