st/mesa: use _mesa_RasterPos() when possible

The st_RasterPos() function goes to great pains to implement the
rasterpos transformation.  It basically uses gallium's draw module to
execute the vertex shader to draw a point, then capture that point's
attributes.

But glRasterPos isn't typically used with a vertex shader so we can
usually use the old/fixed-function implementation which is a lot simpler
and faster.

This can add up for legacy apps that make a lot of calls to glRasterPos.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>

diff --git a/src/mesa/state_tracker/st_cb_rasterpos.c b/src/mesa/state_tracker/st_cb_rasterpos.c
index b9997da..747b414 100644 (file)
--- a/src/mesa/state_tracker/st_cb_rasterpos.c
+++ b/src/mesa/state_tracker/st_cb_rasterpos.c
@@ -39,6 +39,7 @@
 #include "main/imports.h"
 #include "main/macros.h"
 #include "main/feedback.h"
+#include "main/rastpos.h"
 
 #include "st_context.h"
 #include "st_atom.h"
@@ -224,6 +225,15 @@ st_RasterPos(struct gl_context *ctx, const GLfloat v[4])
    struct rastpos_stage *rs;
    const struct gl_client_array **saved_arrays = ctx->Array._DrawArrays;
 
+   if (ctx->VertexProgram._Current == NULL ||
+       ctx->VertexProgram._Current == ctx->VertexProgram._TnlProgram) {
+      /* No vertex shader/program is enabled, used the simple/fast fixed-
+       * function implementation of RasterPos.
+       */
+      _mesa_RasterPos(ctx, v);
+      return;
+   }
+
    if (st->rastpos_stage) {
       /* get rastpos stage info */
       rs = rastpos_stage(st->rastpos_stage);