Re: [Mesa3d-dev] Bitmap and Pixmap Positioning

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

Brian Paul wrote:
> 
> Allen Barnett wrote:
> >
> > Hi,
> >
> > In the routine _mesa_DrawPixels in the file src/drawpix.c, the current
> > raster position is converted to integer coordinates through the IROUND
> > function (round to nearest, I think?). However, in the routine
> > _mesa_Bitmap, the raster position is just cast to a GLint. At least on
> > my system (RedHat 7.1/i386, gcc 2.96), these occasionally give different
> > values, which I can see as inconsistencies in the positioning of bitmaps
> > and pixmaps. I was wondering what the reason was for treating these
> > conversions differently? (_mesa_CopyPixels gets the IROUND, too.)
> 
> Sounds like a bug.  glBitmap should use rounding as well.

Hmmm, I'm not so sure now.  If I change glBitmap to round off the
coordinates then the conformance test fails.  Similarly, if I change
glDraw/CopyPixels to truncate the coordinates then conformance fails
too.

When I have more time I'll look closer at this.  I'll leave things
as-are for now (conformant).

-Brian