[Mesa-dev] Adding support for sRGB framebuffers to EGL

[John Kåre Alsaker]

Hello,

I would like add support for sRGB framebuffers to EGL. Here are my
proposed changes to EGL:

A new EGL_SURFACE_TYPE bit:
EGL_GAMMA_SRGB_BIT - This format supports sRGB framebuffers. This also
means that ARB_framebuffer_sRGB is supported for this format.

New values:
EGL_GAMMA_LINEAR - The gamma is linear.
EGL_GAMMA_SRGB - The gamma is as defined by the sRGB standard.

New EGL surface attribute:
EGL_GAMMA - The gamma of the surface's framebuffer. The default value
is EGL_GAMMA_LINEAR.

When the surface's EGL_GAMMA attribute's value is EGL_GAMMA_SRGB and
this is supported by
the format, reads from this framebuffer will be converted from sRGB
gamma and writes will
be converted to sRGB gamma. This may not apply to all functions in the
client API.

There may be something related to the ARB_framebuffer_sRGB extension
in EGL already, in
which case someone should link me to it.

There's two assumptions behind this proposal. One is that you won't
support sRGB only
formats. The other is that linear gamma and sRGB gamma format support
is the same.
This means that window systems can't add a new linear gamma format
without adding an sRGB
format and the other way around.

I'd like some comments on this proposal and tips on how it could be
implemented in the
mess that is DRI.

Thanks,
John Kåre