XtSetWMColormapWindows
returns immediately if widget is not realized or if count
is zero. Otherwise,
XtSetWMColormapWindows
constructs an ordered list of windows by examining each widget in
list in turn and ignoring the widget if it is not realized,
or adding the widgets window to the window list if the widget is
realized and its colormap resource is different from the colormap
resources of all widgets whose windows are already on the window
list.
Finally,
XtSetWMColormapWindows
stores the resulting window list in the WM_COLORMAP_WINDOWS property
on the specified widgets window.