XPresentPixmap() fails on some driver, not sure why.

Olivier Fourdan fourdan at gmail.com
Fri Jun 9 12:07:23 UTC 2017


Non-work related question... xfwm4 (xfce window manager, from git), have
two different implementations to reduce tearing, GL and Present.

As it now defaults to present, I am receiving more reports of "frozen

I traced it back to XPresentPixmap() failing with BadWindow (the window
being either the COW or the root window, same error)

The funny thing is when catching the XError, the resource id is 0, so if
this is correct, no wonder this would cause a BadWindow - But why would it
use 0 instead of the given COW or root window id?

Now, for that particular bug, the issue is said to have been solved with an
update of presentproto headers version 1.1, pointing commit 8405ee (
https://cgit.freedesktop.org/xorg/proto/presentproto/commit/?id=8405ee) as
the fix.

I cannot tell whether or not this is the fix nor what else could be the
problem because I cannot reproduce this issue locally using intel, nouveau
or modesettings drivers. Meanwhile I am getting more of those and I have no
idea how to debug that further, so I'm open to suggestions...

(For reference, xfce bug is https://bugzilla.xfce.org/show_bug.cgi?id=13257)

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