draw: fix broken polygon offset stage

There were several issues.  We weren't handling different front/back
polygon fill modes.  We weren't checking whether the offset applied to
fill mode vs. line mode vs. point mode.

Fixes problems found with the Visualization Toolkit (VTK) test suite.

Note: This is a candidate for the stable branches.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>

diff --git a/src/gallium/auxiliary/draw/draw_pipe_offset.c b/src/gallium/auxiliary/draw/draw_pipe_offset.c
index 3da52b10624ed7345ee9cfc16efb2df7892e1911..3578525051f463f74dd4e440d60b4de5628be0e8 100644 (file)
--- a/src/gallium/auxiliary/draw/draw_pipe_offset.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_offset.c
@@ -127,10 +127,44 @@ static void offset_first_tri( struct draw_stage *stage,
                              struct prim_header *header )
 {
    struct offset_stage *offset = offset_stage(stage);
+   const struct pipe_rasterizer_state *rast = stage->draw->rasterizer;
+   unsigned fill_mode = rast->fill_front;
+   boolean do_offset;
+
+   if (rast->fill_back != rast->fill_front) {
+      /* Need to check for back-facing triangle */
+      boolean ccw = header->det < 0.0f;
+      if (ccw != rast->front_ccw)
+         fill_mode = rast->fill_back;
+   }
+
+   /* Now determine if we need to do offsetting for the point/line/fill mode */
+   switch (fill_mode) {
+   case PIPE_POLYGON_MODE_FILL:
+      do_offset = rast->offset_tri;
+      break;
+   case PIPE_POLYGON_MODE_LINE:
+      do_offset = rast->offset_line;
+      break;
+   case PIPE_POLYGON_MODE_POINT:
+      do_offset = rast->offset_point;
+      break;
+   default:
+      assert(!"invalid fill_mode in offset_first_tri()");
+      do_offset = rast->offset_tri;
+   }
+
+   if (do_offset) {
+      offset->scale = rast->offset_scale;
+      offset->clamp = rast->offset_clamp;
+      offset->units = (float) (rast->offset_units * stage->draw->mrd);
+   }
+   else {
+      offset->scale = 0.0f;
+      offset->clamp = 0.0f;
+      offset->units = 0.0f;
+   }
 
-   offset->units = (float) (stage->draw->rasterizer->offset_units * stage->draw->mrd);
-   offset->scale = stage->draw->rasterizer->offset_scale;
-   offset->clamp = stage->draw->rasterizer->offset_clamp;
 
    stage->tri = offset_tri;
    stage->tri( stage, header );