XtRealizeWidget, XtIsRealized, XtUnrealizeWidget - realize and unrealize widgets
#include <X11/Intrinsic.h>
void XtRealizeWidget(Widget w);
Boolean XtIsRealized(Widget w);
void XtUnrealizeWidget(Widget w);
If the widget is already realized, XtRealizeWidget simply returns.
  Otherwise, it performs the following:
  - Binds all action names in the widget's translation table to procedures
      (see Section 10.1.2).
- Makes a post-order traversal of the widget tree rooted at the specified
      widget and calls the change_managed procedure of each composite widget
      that has one or more managed children.
- Constructs an XSetWindowAttributes structure filled in with
      information derived from the Core widget fields and calls the
      realize procedure for the widget, which adds any widget-specific
      attributes and creates the X window.
- If the widget is not a subclass of compositeWidgetClass,
      XtRealizeWidget returns; otherwise, it continues and performs the
      following:
  - Descends recursively to each of the widget's managed children and calls
      the realize procedures. Primitive widgets that instantiate children are
      responsible for realizing those children themselves.
- Maps all of the managed children windows that have mapped_when_managed
      True. (If a widget is managed but mapped_when_managed is
      False, the widget is allocated visual space but is not displayed.
      Some people seem to like this to indicate certain states.)
 
If the widget is a top-level shell widget (that is, it has no
    parent), and mapped_when_managed is True, XtRealizeWidget maps
    the widget window.
The XtIsRealized function returns True if the widget
    has been realized, that is, if the widget has a nonzero X window ID.
Some widget procedures (for example, set_values) might wish to
    operate differently after the widget has been realized.
The XtUnrealizeWidget function destroys the windows of an
    existing widget and all of its children (recursively down the widget tree).
    To recreate the windows at a later time, call XtRealizeWidget again.
    If the widget was managed, it will be unmanaged automatically before its
    window is freed.
XtManageChildren(3)
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface