Added origin_lower_left field to pipe_rasterizer_state

This controls whether the window origin is considered to be the lower-left
or upper-left corner.
This effects computation of gl_FragCoord and the application of polygon stipple.

3 files changed, 24 insertions, 7 deletions

diff --git a/src/mesa/pipe/p_state.h b/src/mesa/pipe/p_state.h
index 43b710ff3b6..af65d365bf0 100644
--- a/src/mesa/pipe/p_state.h
+++ b/src/mesa/pipe/p_state.h
@@ -94,6 +94,7 @@ struct pipe_rasterizer_state
    unsigned line_stipple_factor:8;  /**< [1..256] actually */
    unsigned line_stipple_pattern:16;
    unsigned bypass_clipping:1;
+   unsigned origin_lower_left:1;  /**< Is (0,0) the lower-left corner? */
 
    float line_width;
    float point_size;           /**< used when no per-vertex size */
diff --git a/src/mesa/pipe/softpipe/sp_prim_setup.c b/src/mesa/pipe/softpipe/sp_prim_setup.c
index 8d8dceadc5c..2ccf5e2624a 100644
--- a/src/mesa/pipe/softpipe/sp_prim_setup.c
+++ b/src/mesa/pipe/softpipe/sp_prim_setup.c
@@ -480,15 +480,23 @@ static void tri_persp_coeff( struct setup_stage *setup,
 static void
 setup_fragcoord_coeff(struct setup_stage *setup)
 {
-   const int winHeight = setup->softpipe->framebuffer.cbufs[0]->height;
    /*X*/
    setup->coef[0].a0[0] = 0;
    setup->coef[0].dadx[0] = 1.0;
    setup->coef[0].dady[0] = 0.0;
    /*Y*/
-   setup->coef[0].a0[1] = winHeight - 1;
+   if (setup->softpipe->rasterizer->origin_lower_left) {
+      /* y=0=bottom */
+      const int winHeight = setup->softpipe->framebuffer.cbufs[0]->height;
+      setup->coef[0].a0[1] = winHeight - 1;
+      setup->coef[0].dady[1] = -1.0;
+   }
+   else {
+      /* y=0=top */
+      setup->coef[0].a0[1] = 0.0;
+      setup->coef[0].dady[1] = 1.0;
+   }
    setup->coef[0].dadx[1] = 0.0;
-   setup->coef[0].dady[1] = -1.0;
    /*Z*/
    setup->coef[0].a0[2] = setup->posCoef.a0[2];
    setup->coef[0].dadx[2] = setup->posCoef.dadx[2];
diff --git a/src/mesa/pipe/softpipe/sp_quad_stipple.c b/src/mesa/pipe/softpipe/sp_quad_stipple.c
index 04d95989c40..0c42963dfe3 100644
--- a/src/mesa/pipe/softpipe/sp_quad_stipple.c
+++ b/src/mesa/pipe/softpipe/sp_quad_stipple.c
@@ -22,10 +22,18 @@ stipple_quad(struct quad_stage *qs, struct quad_header *quad)
    if (quad->prim == PRIM_TRI) {
       struct softpipe_context *softpipe = qs->softpipe;
       /* need to invert Y to index into OpenGL's stipple pattern */
-      const int y0 = softpipe->framebuffer.cbufs[0]->height - 1 - quad->y0;
-      const int y1 = y0 - 1;
-      const unsigned stipple0 = softpipe->poly_stipple.stipple[y0 % 32];
-      const unsigned stipple1 = softpipe->poly_stipple.stipple[y1 % 32];
+      int y0, y1;
+      uint stipple0, stipple1;
+      if (softpipe->rasterizer->origin_lower_left) {
+         y0 = softpipe->framebuffer.cbufs[0]->height - 1 - quad->y0;
+         y1 = y0 - 1;
+      }
+      else {
+         y0 = quad->y0;
+         y1 = y0 + 1;
+      }
+      stipple0 = softpipe->poly_stipple.stipple[y0 % 32];
+      stipple1 = softpipe->poly_stipple.stipple[y1 % 32];
 
 #if 1
       const int col0 = quad->x0 % 32;