Created attachment 128933 [details]
Screenshot of the issue

Description:

While investigating rendering bugs on Xwayland with nouveau specifically ([1]
and [2]) I realized that some gtk2 output (this Xwayland) is completely
garbled.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1411447
[2] https://bugzilla.gnome.org/show_bug.cgi?id=776255

How reproducible:

Always

Steps to reproduce:

1. Log in a Wayland session (either Weston or GNOME shell) on a Dell M1710 with
a GeForce Go 7950 GTX 
2. Run gtk-demo (the one from gtk2, i.e. not Wayland native but relying on
Xwayland)
3. Start the "Assistant" demo (second starting from the top)

Actual result:

The window is black with random content

Expected result:

The rendering is correct

Additional data:

This issue does not occur when using "shm" and CPU rendering instead of glamor
in Xwayland.

I am not aware of any other hardware where glamor produces such garbled output,
so I suspect an issue with nouveau, but if you reckon it's an issue with glamor
instead, please flip this bug back to xserver/glamor

I have seen other issue with black icons being reported with glamor and nouveau
as well and these do not occur when using the CPU render in weston for example
(https://bugzilla.redhat.com/show_bug.cgi?id=1411447#c12)

In my case, hardware is VGA compatible controller: NVIDIA Corporation G71M
[GeForce Go 7950 GTX] (rev a1) (prog-if 00 [VGA controller])

01:00.0 0300: 10de:0297 (rev a1) (prog-if 00 [VGA controller])
        Subsystem: 1028:019b