clutter: Add color state pipeline capability enum

So far 'color-state' is added, intended to tag pipelines with color
state transformation capabilities. Color state transformation snippets
are tagged with it. Eventually handlers of pipelines will use this
information to on-demand decorate pipelines with color transformation
snippets.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3433>

clutter/clutter/clutter-color-state.c

@@ -835,6 +835,9 @@ clutter_color_state_get_transform_snippet (ClutterColorState *color_state,
   snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_FRAGMENT,
                               globals_source->str,
                               snippet_source->str);
+  cogl_snippet_set_capability (snippet,
+                               CLUTTER_PIPELINE_CAPABILITY,
+                               CLUTTER_PIPELINE_CAPABILITY_COLOR_STATE);
   g_hash_table_insert (snippet_cache,
                        g_memdup2 (&cache_key, sizeof (cache_key)),
                        g_object_ref (snippet));

clutter/clutter/clutter-main.c

@@ -53,6 +53,8 @@ typedef struct
   GDestroyNotify notify;
 } ClutterThreadsDispatch;
 
+G_DEFINE_QUARK (clutter_pipeline_capability, clutter_pipeline_capability)
+
 /* main context */
 static ClutterContext *ClutterCntx       = NULL;
 

clutter/clutter/clutter-main.h

@@ -90,6 +90,15 @@ typedef enum
  */
 #define CLUTTER_PRIORITY_REDRAW         (G_PRIORITY_HIGH_IDLE + 50)
 
+typedef enum _ClutterPipelineCapability
+{
+  CLUTTER_PIPELINE_CAPABILITY_COLOR_STATE,
+} ClutterPipelineCapability;
+
+#define CLUTTER_PIPELINE_CAPABILITY (clutter_pipeline_capability_quark ())
+CLUTTER_EXPORT
+GQuark clutter_pipeline_capability_quark (void);
+
 CLUTTER_EXPORT
 void                    clutter_stage_handle_event              (ClutterStage *stage,
                                                                  ClutterEvent *event);