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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - [Regression, bisected] Screen is darker than expected in Supertuxkart"
href="https://bugs.freedesktop.org/show_bug.cgi?id=92759#c7">Comment # 7</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [Regression, bisected] Screen is darker than expected in Supertuxkart"
href="https://bugs.freedesktop.org/show_bug.cgi?id=92759">bug 92759</a>
from <span class="vcard"><a class="email" href="mailto:deveee@gmail.com" title="Deve <deveee@gmail.com>"> <span class="fn">Deve</span></a>
</span></b>
<pre>I was digging around this bug a bit. Thanks to Ilia Mirkin for the help. Here
is what I noticed:
1. This patch doesn't have a sense.
2. During looking at Supertuxkart code, I noticed that we need srgb-capable
visual for proper working.
3. The difference in intel code, which causes this issue is in intel_screen.c
in intelCreateBuffer() function:
if (mesaVis->redBits == 5)
rgbFormat = MESA_FORMAT_B5G6R5_UNORM;
else if (mesaVis->sRGBCapable)
rgbFormat = MESA_FORMAT_B8G8R8A8_SRGB;
else if (mesaVis->alphaBits == 0)
rgbFormat = MESA_FORMAT_B8G8R8X8_UNORM;
else {
rgbFormat = MESA_FORMAT_B8G8R8A8_SRGB;
fb->Visual.sRGBCapable = true;
}
Before commit 28090b30dd6b5977de085f48c620574214b6b4ba the format
MESA_FORMAT_B8G8R8X8_UNORM was not available, and thus it was using
MESA_FORMAT_B8G8R8A8_SRGB format (which is srgb-capable). Now it is using
MESA_FORMAT_B8G8R8X8_UNORM format, and thus function
glEnable(GL_FRAMEBUFFER_SRGB)
doesn't take effect anymore.
4. I tried to force to use srgb-capable visual by setting
GLX_FRAMEBUFFER_SRGB_CAPABLE_ARB in supertuxkart code with glxChooseFBConfig
function, but it doesn't take any effect.
5. The ugly workaround for this issue in supertuxkart code, is to request
GLX_ALPHA_SIZE > 0. It will fallback to last case in intel code, which I
mentioned upwards:
rgbFormat = MESA_FORMAT_B8G8R8A8_SRGB;
fb->Visual.sRGBCapable = true;
6. The <a class="bz_bug_link
bz_status_NEW "
title="NEW - SRGB dark rendering"
href="show_bug.cgi?id=91817">bug 91817</a> (<a class="bz_bug_link
bz_status_NEW "
title="NEW - SRGB dark rendering"
href="show_bug.cgi?id=91817">https://bugs.freedesktop.org/show_bug.cgi?id=91817</a>) seems to
be related to this bug.
Is there a proper way to force using srgb-capable visual?</pre>
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