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

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

Hello,

I've found that these faster MEMCPY functions were not selected for 16
(or 32-bit for that matter) bit/channel OSMesa.

I enabled them by taking out the check for CHAN_BITS==8 in osmesa.c in
the function osmesa_update_state under where it says /* 4 bytes / pixel
in frame buffer */ ... This could be renamed 4 GLchan / pixel or
someting.

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.

I was also playing around with compiling the osmesa lib with
CHAN_BITS=32 and it broke quite a lot of functions mainly at bit shifts.
How can I compile the lib with some functions modified (the ones that
are going to be called by my 32bit/chan program for checking) and some
others unchanged? Can I safely #if functions out that would not compile
with CHAN_BITS=32, but that are not going to be called? I'm interested
in getting 32bit/chan smoothed triangles rendered.

cheers
jp

read/write functions:

/* Write RGBA pixels to an RGBA buffer.  This is the fastest
span-writer. */
static void
write_rgba_span_rgba( const GLcontext *ctx, GLuint n, GLint x, GLint y,
                      CONST GLchan rgba[][4], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLchan *ptr4 = PIXELADDR4(x, y);
   GLuint i;
   /*ASSERT(CHAN_TYPE == GL_UNSIGNED_BYTE);*/
   if (mask) {
     for (i = 0; i < n; i++, ptr4 += 4) {
         if (mask[i]) {
            PACK_RGBA(ptr4, rgba[i][RCOMP], rgba[i][GCOMP],
                         rgba[i][BCOMP], rgba[i][ACOMP]);
         }
      } 
   }
   else {
      MEMCPY( ptr4, rgba, n * 4 * sizeof(GLchan));
   }
}

/* Read RGBA pixels from an RGBA buffer */
static void
read_rgba_span_rgba( const GLcontext *ctx, GLuint n, GLint x, GLint y,
                     GLchan rgba[][4] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLchan *ptr4 = PIXELADDR4(x, y);
   MEMCPY( rgba, ptr4, n * 4 * sizeof(GLchan) );
}