If we invert Y, need to subtract one from the surface height.
Fixes https://bugs.freedesktop.org/show_bug.cgi?id=26795
for softpipe.
NOTE: This is a candidate for the 7.9 and 7.10 branches.
setup->coef[slot].dady[0] = 0.0;
/*Y*/
setup->coef[slot].a0[1] =
- (spfs->origin_lower_left ? setup->softpipe->framebuffer.height : 0)
+ (spfs->origin_lower_left ? setup->softpipe->framebuffer.height-1 : 0)
+ (spfs->pixel_center_integer ? 0.0 : 0.5);
setup->coef[slot].dadx[1] = 0.0;
setup->coef[slot].dady[1] = spfs->origin_lower_left ? -1.0 : 1.0;