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XtCreateWidget(3Xt)
X11R6
NAME
  XtCreateWidget, XtVaCreateWidget, XtCreateManagedWidget,
  XtVaCreateManagedWidget, XtDestroyWidget - create and destroy widgets

SYNOPSIS
  Widget XtCreateWidget(name, widget_class, parent, args, num_args)
	  String name;
	  WidgetClass widget_class;
	  Widget parent;
	  ArgList args;
	  Cardinal num_args;

  Widget XtVaCreateWidget(name, widget_class, parent, ...)
	  String name;
	  WidgetClass widget_class;
	  Widget parent;

  Widget XtCreateManagedWidget(name, widget_class, parent, args, num_args)
	  String name;
	  WidgetClass widget_class;
	  Widget parent;
	  ArgList args;
	  Cardinal num_args;

  Widget XtVaCreateManagedWidget(name, widget_class, parent, ...)
	  String name;
	  WidgetClass widget_class;
	  Widget parent;

  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.

  ... Specifies the variable argument list to override the resource defaults.

DESCRIPTION
  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.

SEE ALSO
  XtAppCreateShell(3Xt), XtCreatePopupShell(3Xt)

  X Toolkit Intrinsics -- C Language Interface

  Xlib -- C Language X Interface

Index for Section 3Xt

Alphabetical listing for X

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