Remove dependency on TGSI_ATTRIB_x tokens in draw_twoside.c

Added a new draw_set_twoside_attributes() function for specifying which
vertex attributes are to be copied/replaced when a polygon is back-facing.

4 files changed, 60 insertions, 14 deletions

diff --git a/src/mesa/pipe/draw/draw_context.c b/src/mesa/pipe/draw/draw_context.c
index b14de341410..c15f7652a6f 100644
--- a/src/mesa/pipe/draw/draw_context.c
+++ b/src/mesa/pipe/draw/draw_context.c
@@ -67,6 +67,11 @@ struct draw_context *draw_create( void )
 	 draw->vcache.vertex[i] = (struct vertex_header *)(tmp + i * MAX_VERTEX_SIZE);
    }
 
+   draw->attrib_front0 = -1;
+   draw->attrib_back0 = -1;
+   draw->attrib_front1 = -1;
+   draw->attrib_back1 = -1;
+
    return draw;
 }
 
@@ -210,3 +215,39 @@ draw_set_vertex_shader(struct draw_context *draw,
 {
    draw->vertex_shader = *shader;
 }
+
+
+/**
+ * This function is used to tell the draw module about attributes
+ * (like colors) that need to be selected based on front/back face
+ * orientation.
+ *
+ * The logic is:
+ *    if (polygon is back-facing) {
+ *       vertex->attrib[front0] = vertex->attrib[back0];
+ *       vertex->attrib[front1] = vertex->attrib[back1];
+ *    }
+ *
+ * \param front0  first attrib to replace if the polygon is back-facing
+ * \param back0  first attrib to copy if the polygon is back-facing
+ * \param front1  second attrib to replace if the polygon is back-facing
+ * \param back1  second attrib to copy if the polygon is back-facing
+ *
+ * Pass -1 to disable two-sided attributes.
+ */
+void
+draw_set_twoside_attributes(struct draw_context *draw,
+                            uint front0, uint back0,
+                            uint front1, uint back1)
+{
+   /* XXX we could alternately pass an array of front/back attribs if there's
+    * ever need for more than two.  One could imagine a shader extension
+    * that allows arbitrary attributes to be selected based on polygon
+    * orientation...
+    */
+   draw->attrib_front0 = front0;
+   draw->attrib_back0 = back0;
+   draw->attrib_front1 = front1;
+   draw->attrib_back1 = back1;
+}
+
diff --git a/src/mesa/pipe/draw/draw_context.h b/src/mesa/pipe/draw/draw_context.h
index 4c9e64a12d2..21ee18e7cf6 100644
--- a/src/mesa/pipe/draw/draw_context.h
+++ b/src/mesa/pipe/draw/draw_context.h
@@ -92,6 +92,10 @@ void draw_set_vertex_attributes( struct draw_context *draw,
 				 const uint *attrs, const uint *interp_mode,
 				 unsigned nr_attrs );
 
+void draw_set_twoside_attributes(struct draw_context *draw,
+                                 uint front0, uint back0,
+                                 uint front1, uint back1);
+
 unsigned draw_prim_info( unsigned prim, unsigned *first, unsigned *incr );
 
 unsigned draw_trim( unsigned count, unsigned first, unsigned incr );
diff --git a/src/mesa/pipe/draw/draw_private.h b/src/mesa/pipe/draw/draw_private.h
index e61f228d12c..80c97ada329 100644
--- a/src/mesa/pipe/draw/draw_private.h
+++ b/src/mesa/pipe/draw/draw_private.h
@@ -158,6 +158,9 @@ struct draw_context
 
    /** Describes the layout of post-transformation vertices */
    struct vertex_info vertex_info;
+   /** Two-sided attributes: */
+   uint attrib_front0, attrib_back0;
+   uint attrib_front1, attrib_back1;
 
    unsigned nr_vertices;
 
diff --git a/src/mesa/pipe/draw/draw_twoside.c b/src/mesa/pipe/draw/draw_twoside.c
index a05eea41fc2..98eb088035a 100644
--- a/src/mesa/pipe/draw/draw_twoside.c
+++ b/src/mesa/pipe/draw/draw_twoside.c
@@ -61,15 +61,11 @@ static void twoside_begin( struct draw_stage *stage )
 }
 
 
-static INLINE void copy_color( unsigned attr_dst,
+static INLINE void copy_attrib( unsigned attr_dst,
 			       unsigned attr_src,
 			       struct vertex_header *v )
 {
-   if (attr_dst && attr_src) {
-      memcpy( v->data[attr_dst],
-	      v->data[attr_src],
-	      sizeof(v->data[0]) );
-   }
+   COPY_4FV(v->data[attr_dst], v->data[attr_src]);
 }
 
 
@@ -78,14 +74,16 @@ static struct vertex_header *copy_bfc( struct twoside_stage *twoside,
 				       unsigned idx )
 {   
    struct vertex_header *tmp = dup_vert( &twoside->stage, v, idx );
+   const struct draw_context *draw = twoside->stage.draw;
    
-   copy_color( twoside->lookup[TGSI_ATTRIB_COLOR0], 
-	       twoside->lookup[TGSI_ATTRIB_BFC0],
-	       tmp );
-
-   copy_color( twoside->lookup[TGSI_ATTRIB_COLOR1], 
-	       twoside->lookup[TGSI_ATTRIB_BFC1],
-	       tmp );
+   if (draw->attrib_front0) {
+      assert(draw->attrib_back0);
+      copy_attrib(draw->attrib_front0, draw->attrib_back0, tmp);
+   }
+   if (draw->attrib_front1) {
+      assert(draw->attrib_back1);
+      copy_attrib(draw->attrib_front1, draw->attrib_back1, tmp);
+   }
 
    return tmp;
 }
@@ -104,7 +102,7 @@ static void twoside_tri( struct draw_stage *stage,
 
       tmp.det = header->det;
       tmp.edgeflags = header->edgeflags;
-      /* copy back colors to front color slots */
+      /* copy back attribs to front attribs */
       tmp.v[0] = copy_bfc(twoside, header->v[0], 0);
       tmp.v[1] = copy_bfc(twoside, header->v[1], 1);
       tmp.v[2] = copy_bfc(twoside, header->v[2], 2);