[Mesa-dev] [Bug 90264] [Regression, bisected] Tooltip corruption in Chrome

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Jul 21 23:02:01 PDT 2015


--- Comment #38 from Heiko <lil_tux at web.de> ---
(In reply to Antoine Labour from comment #37)
> Can you make glXWaitX "re-evaluate window sizes"? That's the reason we call
> it - we just resized the window, we want to make sure we're drawing to the
> right back buffer. This is a UI workload, we may draw only once and we don't
> want flashing (what a glXSwapBuffers would do), so we want to make sure
> we're drawing to a buffer of the right size - glXWaitX is meant to
> synchronize GL with changes in X.
> In this trace, you're only seeing parts of the calls - in particular there
> should be a glViewport and draws and a glXSwapBuffers after the resize.
> I don't think there's confusion from the app side. Parts of what you're
> seeing is chromium restoring state between its "virtual contexts" (we have
> different subsystems that all need to access GL, and are multiplexed,
> possibly on a single GL context, depending on the version), so it's not
> necessarily surprising to see scissor/viewport that doesn't match the window
> size - until we get to actually draw the picture on screen. In particular,
> the texture is correctly loaded with 370x72, so no confusion there.

Well, most of my findings were pretty vague, because I'm neither a GL expert
nor a mesa expert.

With your hint, I just noticed that dri2_wait_x()/dri2_wait_gl() don't do
anything, because of priv->have_fake_front being zero all the time. It would be
set to 1 for buffer attachments of __DRI_BUFFER_FAKE_FRONT_LEFT, but that's
nowhere set in mesa. Thus gcc just optimized it away completely along with

Seems to be related to [1]?

[1] http://lists.freedesktop.org/archives/mesa-dev/2011-June/008241.html

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