[Bug 88584] [ilk] Font and screen corruption in GTK+ applications

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88584

--- Comment #17 from Tristan Miller <psychonaut at nothingisreal.com> ---
(In reply to Orion Poplawski from comment #16)
> Any progress here?  Anything that can be done to help?  This machine is
> becoming pretty unusable.

If you follow the link to the openSUSE bug from my original report, you'll find
that two workarounds have been suggested (one from Stefan Dirsch in Comment #5
and one from Egbert Eich in Comment #7).  The first one seems to have worked
for me; the second one I haven't tested.

I reproduce Egbert Eich's comment here, as it contains technical information
which may be of use to the Intel driver developers:

> I've chased this issue on Intel Ilk for weeks. This is the same gen
> as you have used for the log you posted on fd.o. I don't know which
> other GPUs you have used.
> 
> I've been able to trace this to the 2D textures COGL uses to store
> glyphs and icons in (as sub-textures) called 'atlases': when a new
> object needs to be cached, COGLS tries to find room in the current
> atlas. If there is no room it tries to resize the atlas. If the
> maximum size of the texture is reached it creates a new 'atlas'.
> 
> What I found was, that once the texture size exceeded 4kx4k (the
> i965_dri.so driver announces a max texture level of 14 - ie. a size
> of 8kx8k) the content got corrupted, ie some elemends got lost during
> copying. However, what I also found was that this depended on the
> blit mode used for atlases: the blit modes can be specified with the
> environment variable COGL_ATLAS_DEFAULT_BLIT_MODE - available
> settings are: 'texture-render'. 'framebuffer', 'copy-tex-sub-image',
> 'get-tex-data'. 'texture-render' is the default. Specifying any of
> the others made the issue go away for me.
> 
> I've never gotten around to dump the opengl state and shaders used in
> this mode to generate a simple test case which would have allowed to
> debug the intel driver.
> 
> The workaround I suggested to our customer was to set the environment
> variable:
> 
> COGL_ATLAS_DEFAULT_BLIT_MODE=framebuffer
> 
> in /etc/environment. This made things work for him
> 
> You may want to give this a try as well.
> 
> Please let me know if it does the job.

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