[PATCH] glx: do not pick sRGB config for 32-bit RGBA visual

[Thomas Hellstrom]

On 12/11/2017 06:53 AM, Tapani Pälli wrote:
> Hi;
>
> Any comments? Without this change there will be issues with certain 
> Linux desktops when distributions start to use Mesa 17.4.
>

Tapani,
Did you actually try this with latest xserver master without this patch 
applied, or with 1.19 only?
With it you should have a number of 32 bit fbconfig both with and 
without sRGB and typically the non-sRGB fbconfigs would be first in the 
list so the built-in 32-bit visual would pick the non-sRGB visuals 
anyway. So with xserver master your patch wouldn't have any effect at 
all. At most it would reorder the 32-bit visuals?

There was a previous problem when we only had a single 32-bit visual and 
it got assigned an sRGB visual, because the mesa GLX layer doesn't allow 
sRGB fbconfigs in glxChooseFBConfig. I think there's where the real 
problem is (or one of them), since at least kwin uses glxChooseFBConfig 
to look up an fbconfig list to match the fbconfig of the 32-bit visual. 
When that problem was fixed in xserver commit f84e59a4 it seemed all 
drivers except Intel's worked fine again.

FWIW, Nvidia's proprietary driver only exposes sRGB fbconfigs so 
apparently the applications work fine with them.

Now with non-master X servers (1.19 and earlier) your patch, while 
fixing things on some drivers, might actually break others, because 
there are no other usable 32-bit fbconfigs left. It depends on the 
number of fbconfigs the driver is exposing.

So to summarize:

1) Your patch shouldn't really have any effect on Xorg master other than 
reordering the 32-bit visuals and if so only if sRGB fbconfigs are 
listed first by the driver.
2) The fix for non-master X servers  would probably be to allow sRGB 
fbconfigs in mesa's glxChooseFBConfigs so that apps can actually find 
the fbconfig associated with the single 32-bit visual.
3) If there are any remaining problems, they are probably driver related.

/Thomas





> On 11/28/2017 09:23 AM, Tapani Pälli wrote:
>> This fixes blending issues seen with kwin and gnome-shell when
>> 32bit visual has sRGB capability set.
>>
>> Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
>> Bugzilla: 
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D103699&d=DwIGaQ&c=uilaK90D4TOVoH58JNXRgQ&r=wnSlgOCqfpNS4d02vP68_E9q2BNMCwfD2OZ_6dCFVQQ&m=ui-fsRhvz5hb1wtFp3g-rGtMhklZIsnn4P3UZ3D6z0s&s=IS0-fxjcgga5I5ISJ_b9nJbZiRewgoSkKXIM40JUUDQ&e=
>> Bugzilla: 
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D103646&d=DwIGaQ&c=uilaK90D4TOVoH58JNXRgQ&r=wnSlgOCqfpNS4d02vP68_E9q2BNMCwfD2OZ_6dCFVQQ&m=ui-fsRhvz5hb1wtFp3g-rGtMhklZIsnn4P3UZ3D6z0s&s=Y_58iAZqhtAjhJ1sdV4G3nogUnJf1eI7dYmOScyKmh8&e=
>> Bugzilla: 
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D103655&d=DwIGaQ&c=uilaK90D4TOVoH58JNXRgQ&r=wnSlgOCqfpNS4d02vP68_E9q2BNMCwfD2OZ_6dCFVQQ&m=ui-fsRhvz5hb1wtFp3g-rGtMhklZIsnn4P3UZ3D6z0s&s=_qzmVp96ZC9XYBJXLUVI4_0prbenD-Wr7zgp8EpiSeo&e=
>> ---
>>   glx/glxscreens.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/glx/glxscreens.c b/glx/glxscreens.c
>> index 73444152a..596d972e0 100644
>> --- a/glx/glxscreens.c
>> +++ b/glx/glxscreens.c
>> @@ -271,6 +271,11 @@ pickFBConfig(__GLXscreen * pGlxScreen, VisualPtr 
>> visual)
>>           /* If it's the 32-bit RGBA visual, demand a 32-bit 
>> fbconfig. */
>>           if (visual->nplanes == 32 && config->rgbBits != 32)
>>               continue;
>> +        /* If it's the 32-bit RGBA visual, do not pick sRGB capable 
>> config.
>> +         * This can cause issues with compositors that are not sRGB 
>> aware.
>> +         */
>> +        if (visual->nplanes == 32 && config->sRGBCapable == GL_TRUE)
>> +            continue;
>>           /* Can't use the same FBconfig for multiple X visuals.  I 
>> think. */
>>           if (config->visualID != 0)
>>               continue;
>>
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