mesa: Handle updating texture state for buffer textures.

We have to skip some work that wants to look at texture images, since
buffer textures don't have any of that complexity.

Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/main/texobj.c

@@ -449,6 +449,14 @@ _mesa_test_texobj_completeness( const struct gl_context *ctx,
    t->_BaseComplete = GL_TRUE;
    t->_MipmapComplete = GL_TRUE;
 
+   if (t->Target == GL_TEXTURE_BUFFER) {
+      /* Buffer textures are always considered complete.  The obvious case where
+       * they would be incomplete (no BO attached) is actually specced to be
+       * undefined rendering results.
+       */
+      return;
+   }
+
    /* Detect cases where the application set the base level to an invalid
     * value.
     */

src/mesa/main/texstate.c

@@ -390,6 +390,10 @@ update_tex_combine(struct gl_context *ctx, struct gl_texture_unit *texUnit)
 {
    struct gl_tex_env_combine_state *combine;
 
+   /* No combiners will apply to this. */
+   if (texUnit->_Current->Target == GL_TEXTURE_BUFFER)
+      return;
+
    /* Set the texUnit->_CurrentCombine field to point to the user's combiner
     * state, or the combiner state which is derived from traditional texenv
     * mode.