[PATCH xserver 1/3] present: Only update screen pixmap from flip pixmap once per unflip

[Chris Wilson]

On Fri, Feb 19, 2016 at 11:39:10AM +0900, Michel Dänzer wrote:
> From: Michel Dänzer <michel.daenzer at amd.com>
> 
> present_unflip may be called several times from present_check_flip_window
> during the same unflip. We can only copy to the screen pixmap the first
> time, otherwise we may scribble over other windows. The flip pixmap
> contents don't get updated after the first time anyway.
> 
> Fixes at least the following problems, which were introduced by commit
> 806470b9 ("present: Copy unflip contents back to the Screen Pixmap"):
> 
> On xfwm4 without compositing, run glxgears and put its window into
> fullscreen mode to start flipping. While in fullscreen, open the xfwm4
> window menu by pressing Alt-Space. The window menu was invisible most
> of the time because it was getting scribbled over by a repeated unflip
> copy.
> 
> When switching a flipping window out of fullscreen, a repeated unflip
> copy could leave artifacts of the flip pixmap on the desktop.
> 
> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>

And the ordering is better: we should do the restoration of the contents
before we restore the window->pixmap linkage.

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre