[PATCH weston v2 00/16] Fix pixman-renderer cropping

[Bill Spitzak]

This all looks really good to me.

It is possible to avoid "GL coordinates" even in GL. Set the projection 
matrix to an ortho matrix:

   glMatrixMode(GL_PROJECTION);
   glLoadIdentity()
   glOrtho(0, width, height, 0, -1, 1);
   glTranslate(-width/2, -height/2, 0);
   glMatrixMode(GL_MODELVIEW);

I remember in our code we did this by directly with glLoadMatrix. This 
avoided any error with how the center was calculated, and made the Z 
output to be zero. However I am unsure if that is portable to all devices.

This would reduce the number of coordinate spaces you need to think about.