5.7 Subwindow Mode
The subwindow_mode member of
XGCValues controls whether subwindows obscure their
parent for purposes of drawing on the parent. This member is set with
XSetSubwindowMode().
The value ClipByChildren sets the default
condition, in which drawing into the area of a window obscured by its
visible children produces no effect.
If the subwindow_mode is set to
IncludeInferiors, drawing appears through visible
children even when they have opaque backgrounds. The use of
IncludeInferiors on a window of depth 1 with mapped
inferiors of differing depth is not illegal, but the results are not
defined in standard Xlib.
One familiar use of IncludeInferiors is the
window manager’s “rubber banding” of window outlines while they are
being moved or resized. The outline is drawn on the root window with the
GC set to IncludeInferiors.
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