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Roland Scheidegger wrote:

> The plan is to implement a rgba signed 8-bit format (to keep the
> extension simple) and reuse the Nvidia enums (certainly the full set of
> rgb/rgba/luminance/etc. could be exposed, but there are no plans for
> that, it could be done in another extension - note though if you'd also
> wanted to expose red and reg_green formats you'd need new enums). There
> is in fact another extension which exposes signed formats but only
> compressed ones (ARB_texture_compression_rgtc, core 3.0), so some of the
> language between those extensions will be the same.

Given the way things are progressing with OpenGL, it is best to not
expose new luminance, alpha, intensity, etc. texture formats.  Exposing
the internal formats of:

 * SIGNED_R
 * SIGNED_R8
 * SIGNED_RG
 * SIGNED_RG8
 * SIGNED_RGB
 * SIGNED_RGB8
 * SIGNED_RGBA
 * SIGNED_RGBA8

The last half would use the Nvidia enums, and the first half would, as
you point out, need new enums.  It looks like Mesa has unused enums in
the range 0x8BB8 - 0x8BBF assigned to it.  That looks like it should be
just enough.

It seems like a new set of type enums is in order, but I'm not sure what
they should be.  The ATI extension doesn't provide any.  I'm assuming
they expect applications to always use GL_DUDV_ATI with GL_SIGNED_BYTE.
 The Nvidia extension provides GL_UNSIGNED_INT_S8_S8_8_8_NV and
GL_UNSIGNED_INT_8_8_S8_S8_REV_NV for use with the GL_DSDT_MAG_VIB_NV
format.  This format uses mixed signed and unsigned values.

It seems like either GL_SHORT_8_8 or GL_UNSIGNED_SHORT_S8_S8 for RG
would be correct.  As ugly as it is, I think the later is the right one.
 The packed type itself is unsigned short, but it contains signed 8-bit
values.  That would mean:

 * GL_UNSIGNED_SHORT_S8_S8
 * GL_UNSIGNED_SHORT_S8_S8_REV
 * GL_UNSIGNED_INT_S8_S8_S8_S8
 * GL_UNSIGNED_INT_S8_S8_S8_S8_REV

That's exactly 8 new enums. :)
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