attribute: Adds support for constant CoglAttributes

This makes it possible to create vertex attributes that efficiently
represent constant values without duplicating the constant for every
vertex. This adds the following new constructors for constant
attributes:

  cogl_attribute_new_const_1f
  cogl_attribute_new_const_2fv
  cogl_attribute_new_const_3fv
  cogl_attribute_new_const_4fv
  cogl_attribute_new_const_2f
  cogl_attribute_new_const_3f
  cogl_attribute_new_const_4f
  cogl_attribute_new_const_2x2fv
  cogl_attribute_new_const_3x3fv
  cogl_attribute_new_const_4x4fv

Reviewed-by: Neil Roberts <neil@linux.intel.com>

(cherry picked from commit 6507216f8030e84dcf2e63b8ecfe906ac47f2ca7)

1 files changed, 17 insertions, 5 deletions

diff --git a/cogl/cogl-attribute-private.h b/cogl/cogl-attribute-private.h
index beb5609b..d38f4e6c 100644
--- a/cogl/cogl-attribute-private.h
+++ b/cogl/cogl-attribute-private.h
@@ -32,6 +32,7 @@
 #include "cogl-attribute.h"
 #include "cogl-framebuffer.h"
 #include "cogl-pipeline-private.h"
+#include "cogl-boxed-value.h"
 
 typedef enum
 {
@@ -55,14 +56,25 @@ struct _CoglAttribute
 {
   CoglObject _parent;
 
-  CoglAttributeBuffer *attribute_buffer;
   const CoglAttributeNameState *name_state;
-  size_t stride;
-  size_t offset;
-  int n_components;
-  CoglAttributeType type;
   CoglBool normalized;
 
+  CoglBool is_buffered;
+
+  union {
+    struct {
+      CoglAttributeBuffer *attribute_buffer;
+      size_t stride;
+      size_t offset;
+      int n_components;
+      CoglAttributeType type;
+    } buffered;
+    struct {
+      CoglContext *context;
+      CoglBoxedValue boxed;
+    } constant;
+  } d;
+
   int immutable_ref;
 };