draw: fix primitive restart bug by using the index buffer offset

The code which scans the index buffer for restart indexes wasn't adding
the index buffer offset so we were always starting at offset=0.  The
offset is usually zero so it wasn't noticed before.

Fixes a failure in the piglit primitive-restart test when testing
vertex data + index data in a single VBO.

NOTE: This is a candidate for the 8.0 branch.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/gallium/auxiliary/draw/draw_pt.c b/src/gallium/auxiliary/draw/draw_pt.c
index dbe5e9470b2..2c4edc0f946 100644
--- a/src/gallium/auxiliary/draw/draw_pt.c
+++ b/src/gallium/auxiliary/draw/draw_pt.c
@@ -368,25 +368,28 @@ draw_pt_arrays_restart(struct draw_context *draw,
 
    if (draw->pt.user.elts) {
       /* indexed prims (draw_elements) */
+      const char *elts =
+         (const char *) draw->pt.user.elts + draw->pt.index_buffer.offset;
+
       cur_start = start;
       cur_count = 0;
 
       switch (draw->pt.user.eltSize) {
       case 1:
          {
-            const ubyte *elt_ub = (const ubyte *) draw->pt.user.elts;
+            const ubyte *elt_ub = (const ubyte *) elts;
             PRIM_RESTART_LOOP(elt_ub);
          }
          break;
       case 2:
          {
-            const ushort *elt_us = (const ushort *) draw->pt.user.elts;
+            const ushort *elt_us = (const ushort *) elts;
             PRIM_RESTART_LOOP(elt_us);
          }
          break;
       case 4:
          {
-            const uint *elt_ui = (const uint *) draw->pt.user.elts;
+            const uint *elt_ui = (const uint *) elts;
             PRIM_RESTART_LOOP(elt_ui);
          }
          break;