[cogl-color] Adds a cogl_color_equal() function

CoglColors shouldn't be compared using memcmp since they may contain
uninitialized padding bytes.

The prototype is also suitable for passing to g_hash_table_new as the
key_equal_func.

_cogl_pango_display_list_add_texture now uses this instead of memcmp.

clutter/cogl/cogl-color.h

@@ -240,6 +240,22 @@ float     cogl_color_get_alpha       (const CoglColor *color);
  */
 void cogl_color_premultiply (CoglColor *color);
 
+/**
+ * cogl_color_equal:
+ * @v1: a #CoglColor
+ * @v2: a #CoglColor
+ *
+ * Compares two #CoglColor<!-- -->s and checks if they are the same.
+ *
+ * This function can be passed to g_hash_table_new() as the @key_equal_func
+ * parameter, when using #CoglColor<!-- -->s as keys in a #GHashTable.
+ *
+ * Return value: %TRUE if the two colors are the same.
+ *
+ * Since: 1.0
+ */
+gboolean  cogl_color_equal (gconstpointer v1, gconstpointer v2);
+
 G_END_DECLS
 
 #endif /* __COGL_COLOR_H__ */

clutter/cogl/common/cogl-color.c

@@ -25,6 +25,8 @@
 #include "config.h"
 #endif
 
+#include <string.h>
+
 #include "cogl.h"
 #include "cogl-color.h"
 #include "cogl-fixed.h"
@@ -184,3 +186,16 @@ cogl_set_source_color4f (float red,
   cogl_color_set_from_4f (&c, red, green, blue, alpha);
   cogl_set_source_color (&c);
 }
+
+gboolean
+cogl_color_equal (gconstpointer v1, gconstpointer v2)
+{
+  const guint32 *c1 = v1, *c2 = v2;
+
+  g_return_val_if_fail (v1 != NULL, FALSE);
+  g_return_val_if_fail (v2 != NULL, FALSE);
+
+  /* XXX: We don't compare the padding */
+  return *c1 == *c2 ? TRUE : FALSE;
+}
+

clutter/pango/cogl-pango-display-list.c

@@ -138,8 +138,7 @@ _cogl_pango_display_list_add_texture (CoglPangoDisplayList *dl,
       && (node = dl->last_node->data)->type == COGL_PANGO_DISPLAY_LIST_TEXTURE
       && node->d.texture.texture == texture
       && (dl->color_override
-          ? (node->color_override && !memcmp (&dl->color, &node->color,
-                                              sizeof (CoglColor)))
+          ? (node->color_override && cogl_color_equal (&dl->color, &node->color))
           : !node->color_override))
     {
       /* Get rid of the vertex buffer so that it will be recreated */