softpipe: support all TGSI fragment coord conventions (v4)

Changes in v4:
- Rebase and modify for changes in previous patches

Changes in v3:
- Use positive caps instead of negative caps

Changes in v2:
- Now takes the fragment convention directly from the fragment shader

Adds internal support for all fragment coord conventions to softpipe.

This patch is not required for use with the current state trackers, but it
allows softpipe to run any TGSI program and enhances performance.

1 files changed, 7 insertions, 4 deletions

diff --git a/src/gallium/drivers/softpipe/sp_setup.c b/src/gallium/drivers/softpipe/sp_setup.c
index ba1f0f0b2e..bb1bff581c 100644
--- a/src/gallium/drivers/softpipe/sp_setup.c
+++ b/src/gallium/drivers/softpipe/sp_setup.c
@@ -504,21 +504,24 @@ static void tri_persp_coeff( struct setup_context *setup,
 
 /**
  * Special coefficient setup for gl_FragCoord.
- * X and Y are trivial, though Y has to be inverted for OpenGL.
+ * X and Y are trivial, though Y may have to be inverted for OpenGL.
  * Z and W are copied from posCoef which should have already been computed.
  * We could do a bit less work if we'd examine gl_FragCoord's swizzle mask.
  */
 static void
 setup_fragcoord_coeff(struct setup_context *setup, uint slot)
 {
+   struct sp_fragment_shader* spfs = setup->softpipe->fs;
    /*X*/
-   setup->coef[slot].a0[0] = 0;
+   setup->coef[slot].a0[0] = spfs->pixel_center_integer ? 0.0 : 0.5;
    setup->coef[slot].dadx[0] = 1.0;
    setup->coef[slot].dady[0] = 0.0;
    /*Y*/
-   setup->coef[slot].a0[1] = 0.0;
+   setup->coef[slot].a0[1] =
+		   (spfs->origin_lower_left ? setup->softpipe->framebuffer.height : 0)
+		   + (spfs->pixel_center_integer ? 0.0 : 0.5);
    setup->coef[slot].dadx[1] = 0.0;
-   setup->coef[slot].dady[1] = 1.0;
+   setup->coef[slot].dady[1] = spfs->origin_lower_left ? -1.0 : 1.0;
    /*Z*/
    setup->coef[slot].a0[2] = setup->posCoef.a0[2];
    setup->coef[slot].dadx[2] = setup->posCoef.dadx[2];