draw: add switch for drivers to force vertex data passthrough

src/gallium/auxiliary/draw/draw_context.c

@@ -272,6 +272,14 @@ draw_enable_point_sprites(struct draw_context *draw, boolean enable)
 }
 
 
+void
+draw_set_force_passthrough( struct draw_context *draw, boolean enable )
+{
+   draw_do_flush( draw, DRAW_FLUSH_STATE_CHANGE );
+   draw->force_passthrough = enable;
+}
+
+
 /**
  * Ask the draw module for the location/slot of the given vertex attribute in
  * a post-transformed vertex.

src/gallium/auxiliary/draw/draw_context.h

@@ -160,6 +160,9 @@ void draw_set_render( struct draw_context *draw,
 void draw_set_driver_clipping( struct draw_context *draw,
                                boolean bypass_clipping );
 
+void draw_set_force_passthrough( struct draw_context *draw, 
+                                 boolean enable );
+
 /*******************************************************************************
  * Draw pipeline 
  */

src/gallium/auxiliary/draw/draw_private.h

@@ -163,12 +163,15 @@ struct draw_context
 
    struct {
       boolean bypass_clipping;
+      boolean bypass_vs;
    } driver;
 
    boolean flushing;         /**< debugging/sanity */
    boolean suspend_flushing; /**< internally set */
    boolean bypass_clipping;  /**< set if either api or driver bypass_clipping true */
 
+   boolean force_passthrough; /**< never clip or shade */
+
    /* pipe state that we need: */
    const struct pipe_rasterizer_state *rasterizer;
    struct pipe_viewport_state viewport;

src/gallium/auxiliary/draw/draw_pt.c

@@ -69,26 +69,26 @@ draw_pt_arrays(struct draw_context *draw,
          return TRUE;
    }
 
+   if (!draw->force_passthrough) {
+      if (!draw->render) {
+         opt |= PT_PIPELINE;
+      }
+      
+      if (draw_need_pipeline(draw,
+                             draw->rasterizer,
+                             prim)) {
+         opt |= PT_PIPELINE;
+      }
 
-   if (!draw->render) {
-      opt |= PT_PIPELINE;
+      if (!draw->bypass_clipping && !draw->pt.test_fse) {
+         opt |= PT_CLIPTEST;
+      }
+      
+      if (!draw->rasterizer->bypass_vs) {
+         opt |= PT_SHADE;
+      }
    }
-
-   if (draw_need_pipeline(draw,
-                          draw->rasterizer,
-                          prim)) {
-      opt |= PT_PIPELINE;
-   }
-
-   if (!draw->bypass_clipping && !draw->pt.test_fse) {
-      opt |= PT_CLIPTEST;
-   }
-
-   if (!draw->rasterizer->bypass_vs) {
-      opt |= PT_SHADE;
-   }
-
-
+      
    if (opt == 0) 
       middle = draw->pt.middle.fetch_emit;
    else if (opt == PT_SHADE && !draw->pt.no_fse)