Mesa (master): i915: Handle provoking vertex in intelFastRenderClippedPoly ()

[Ian Romanick]

Module: Mesa
Branch: master
Commit: 303895655c6ed837e3d867a450f4322404e86a88
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=303895655c6ed837e3d867a450f4322404e86a88

Author: Ville Syrjälä <ville.syrjala at linux.intel.com>
Date:   Mon Mar 23 14:47:25 2015 +0200

i915: Handle provoking vertex in intelFastRenderClippedPoly()

intelFastRenderClippedPoly() renders the polygon using triangles. For
polygons the provoking vertex is always the first one, and currently
this function assumes that the provoking vertex for triangles is the
last one. In case the user changed the provoking vertex convention,
the hardware may be configured to treat the first vertex of triangles
as the provoking vertex. So check the convention and emit the triangles
in the appropriate order to avoid having to change the hardware
provoking vertex convention for rendering polygons.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

---

 src/mesa/drivers/dri/i915/intel_tris.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i915/intel_tris.c b/src/mesa/drivers/dri/i915/intel_tris.c
index 1554613..6133c23 100644
--- a/src/mesa/drivers/dri/i915/intel_tris.c
+++ b/src/mesa/drivers/dri/i915/intel_tris.c
@@ -928,10 +928,18 @@ intelFastRenderClippedPoly(struct gl_context * ctx, const GLuint * elts, GLuint
    const GLuint *start = (const GLuint *) V(elts[0]);
    int i, j;
 
-   for (i = 2; i < n; i++) {
-      COPY_DWORDS(j, vb, vertsize, V(elts[i - 1]));
-      COPY_DWORDS(j, vb, vertsize, V(elts[i]));
-      COPY_DWORDS(j, vb, vertsize, start);
+   if (ctx->Light.ProvokingVertex == GL_LAST_VERTEX_CONVENTION) {
+      for (i = 2; i < n; i++) {
+         COPY_DWORDS(j, vb, vertsize, V(elts[i - 1]));
+         COPY_DWORDS(j, vb, vertsize, V(elts[i]));
+         COPY_DWORDS(j, vb, vertsize, start);
+      }
+   } else {
+      for (i = 2; i < n; i++) {
+         COPY_DWORDS(j, vb, vertsize, start);
+         COPY_DWORDS(j, vb, vertsize, V(elts[i - 1]));
+         COPY_DWORDS(j, vb, vertsize, V(elts[i]));
+      }
    }
 }