Re: [Mesa3d-dev] read/write_rgba_span_rgba for OSMesa CHAN_BITS=16

[J.P. D. <jpd...@cs...>]

Brian Paul wrote:
> 
> "J.P. Delport" wrote:
>
> > I also did some GLchan fixes in read/write_rgba_span_rgba in osmesa.c
> >
> > The functions appear to work correctly for 16 bit/channel (and should
> > for 32 bit). They follow at the bottom. I don't know if the ASSERT in
> > the write function can be removed completely.
> 
> This is incorrect.  The write_rgba_span_rgba() function will only work
> correctly for 8-bit channels.  The reason is we're using a GLuint to
> store 4 8-bit channels at once as a dword.  By storing 4 bytes at once
> (without any swizzling) we can get slightly better performance.  But
> if we're storing > 4 bytes or need swizzling, we need to use the slower
> write_rgba_span() function.

Sorry, I missed the idea behind the use of the GLint. Still, the case
for CHAN_BITS=16 with no swizzling is also a special case and could be
made faster by using MEMCPY, escpecially when there is no mask.

Also: in the function write_rgb_span the alpha values passed to
PACK_RGBA are 255???

jp