Re: [Mesa3d-dev] GLchan and texture images

[Gareth H. <ga...@va...>]

Brian Paul wrote:
> 
> With 3.5 drivers can implement _any_ format or type of texture images they
> want.  They just have to provide the appropriate FetchTexel() functions
> so the software fallbacks can operate.  FetchTexel() should return GLchan
> values.
> 
> But yes, the s/w Mesa teximage routines should be written with the GLchan
> type so that 16-bit and float color components will be possible.

texImage->TexFormat can't be NULL, so there has to be texure formats for
the s/w texture images.  I'm trying to make this as clean as possible,
as the old "Mesa formats" were based on GLubyte per channel only.

> Originally, the "Mesa formats" and texutil.[ch] were just helper routines
> for drivers; core Mesa knew nothing about them.  It sounds like you're
> bringing that into core Mesa.  I'm not sure of all the ramifications of
> that.

Only the texture format stuff.  The texutil code is used by drivers to
convert into hardware-friendly texture formats, but the texstore
utilities need to have corresponding gl_texture_format structures for
tightly-packed GLchan images.

Now, the gl_texture_image structure has a pointer to a gl_texture_format
structure that defines the internal format of the image.  The
gl_texture_format has the component sizes, bytes per texel, and custom
FetchTexel routines that are plugged into the main gl_texture_image
structure.

> It was compiling about a month ago.  I started testing OSMesa with 16-bit
> color channels but didn't do any verification.   It's definitely not
> ready for prime time yet.

Okay, I was just wondering if it was possible to test it out.  Some of
the colormac.h macros look a little wrong, particularly this one at 16
bits:

#define UBYTE_TO_CHAN(b)  ((GLchan) (((b) << 8) | (b)))

-- Gareth