XComposite Overlay Window usage

Jochen Keil j.keil at gmx.de
Mon Sep 23 04:23:08 PDT 2013


I'm trying to write an application with which I'd like to draw "over"
other windows. So far my attempts have been:

* Drawing right into other window's backing pixmap
(XCompositeNameWindowPixmap). This messes up some applications but can
be fixed by calling XClearArea. However, this produces a Damage Event
which is also not nice.

* Drawing to an transparent overlay window I create myself: Main problem
is to keep this window always on top of of all the other windows
(repeated calls to XRaiseWindow, possible flicker) + requires a
compositing manager.

* Drawing to the XComposite overlay window (XCompositeGetOverlayWindow),
respectively a child window of it. Only works if the overlay window is
mapped, but then everything appears to "frozen". I realize that I can
handle this by using XFixes + shapes for input and drawing all windows
to the overlay window, but then I am doing what a compositor is meant for.

So my question is: Can I somehow draw on a transparent surface/window
above all other windows without semi-implementing a compositing manager?

Thanks and best wishes,


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