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

[Brian P. <br...@va...>]

"J.P. Delport" wrote:
> 
> 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.

Yes, that could be done.  Feel free to submit a patch. :)


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

I'm replacing 255 with CHAN_MAX.  Thanks.

-Brian