[cogl] pipeline: Avoid reseting texture target for NULL textures

[Robert Bragg <rbragg src gnome org>]

commit 098a19380215104f4dcf3474b4155f2d1b04f03d
Author: Robert Bragg <robert linux intel com>
Date:   Mon Jun 27 21:09:27 2011 +0100

    pipeline: Avoid reseting texture target for NULL textures
    
    When setting a NULL texture on a CoglPipeline we would also reset the
    texture target to a dummy value of 0. Reseting the target also had the
    effect of making fragends discard any associated program. In cases where
    the NULL texture was only transient until a replacement texture could be
    set we were re-running lots of redundant codegen and shader
    compilations.
    
    Signed-off-by: Neil Roberts <neil linux intel com>

 cogl/cogl-pipeline.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)
---
diff --git a/cogl/cogl-pipeline.c b/cogl/cogl-pipeline.c
index 45fc077..aba4d22 100644
--- a/cogl/cogl-pipeline.c
+++ b/cogl/cogl-pipeline.c
@@ -2384,10 +2384,9 @@ get_texture_target (CoglHandle texture)
   GLuint ignore_handle;
   GLenum gl_target;
 
-  if (texture)
-    cogl_texture_get_gl_texture (texture, &ignore_handle, &gl_target);
-  else
-    return 0;/* XXX: An invalid GL target enum */
+  g_return_val_if_fail (texture, 0);
+
+  cogl_texture_get_gl_texture (texture, &ignore_handle, &gl_target);
 
   return gl_target;
 }
@@ -2410,9 +2409,14 @@ cogl_pipeline_set_layer_texture (CoglPipeline *pipeline,
    * do need to see if they use the same texture targets. Making this
    * distinction is much simpler if they are in different state
    * groups.
+   *
+   * Note: if a NULL texture is set then we leave the target unchanged
+   * so we can avoid needlessly invalidating any associated fragment
+   * program.
    */
-  _cogl_pipeline_set_layer_texture_target (pipeline, layer_index,
-                                           get_texture_target (texture));
+  if (texture)
+    _cogl_pipeline_set_layer_texture_target (pipeline, layer_index,
+                                             get_texture_target (texture));
   _cogl_pipeline_set_layer_texture_data (pipeline, layer_index, texture);
 }