clutter: Remove ability to externally set sync-to-vblank

Externally setting the sync-to-vblank setting was a feature
added as a workaround to old Intel and ATI graphic cards, and
is not needed anymore. Furthermore, it doesn't make sense to
change it on a compositor whatsoever.

This commit removes all the ways to externally change this
setting, as well as the now unused API.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/191

clutter/clutter/clutter-main.c

@@ -255,16 +255,6 @@ clutter_config_read_from_key_file (GKeyFile *keyfile)
   else
     clutter_enable_accessibility = bool_value;
 
-  bool_value =
-    g_key_file_get_boolean (keyfile, ENVIRONMENT_GROUP,
-                            "SyncToVblank",
-                            &key_error);
-
-  if (key_error != NULL)
-    g_clear_error (&key_error);
-  else
-    clutter_sync_to_vblank = bool_value;
-
   int_value =
     g_key_file_get_integer (keyfile, ENVIRONMENT_GROUP,
                             "DefaultFps",
@@ -1491,10 +1481,6 @@ pre_parse_hook (GOptionContext  *context,
   if (env_string)
     clutter_use_fuzzy_picking = TRUE;
 
-  env_string = g_getenv ("CLUTTER_VBLANK");
-  if (g_strcmp0 (env_string, "none") == 0)
-    clutter_sync_to_vblank = FALSE;
-
   return _clutter_backend_pre_parse (backend, error);
 }
 
@@ -3635,12 +3621,6 @@ _clutter_set_sync_to_vblank (gboolean sync_to_vblank)
   clutter_sync_to_vblank = !!sync_to_vblank;
 }
 
-gboolean
-_clutter_get_sync_to_vblank (void)
-{
-  return clutter_sync_to_vblank;
-}
-
 void
 _clutter_debug_messagev (const char *format,
                          va_list     var_args)

clutter/clutter/clutter-mutter.h

@@ -34,9 +34,6 @@
 CLUTTER_EXPORT
 void clutter_set_custom_backend_func (ClutterBackend *(* func) (void));
 
-CLUTTER_EXPORT
-gboolean        _clutter_get_sync_to_vblank     (void);
-
 CLUTTER_EXPORT
 int64_t clutter_stage_get_frame_counter (ClutterStage *stage);
 

clutter/clutter/x11/clutter-stage-x11.c

@@ -631,8 +631,7 @@ clutter_stage_x11_realize (ClutterStageWindow *stage_window)
 
   stage_x11->onscreen = cogl_onscreen_new (backend->cogl_context, width, height);
 
-  cogl_onscreen_set_swap_throttled (stage_x11->onscreen,
-                                    _clutter_get_sync_to_vblank ());
+  cogl_onscreen_set_swap_throttled (stage_x11->onscreen, TRUE);
   stage_x11->frame_closure =
     cogl_onscreen_add_frame_callback (stage_x11->onscreen,
                                       frame_cb,

src/backends/native/meta-renderer-native.c

@@ -2729,9 +2729,6 @@ meta_renderer_native_create_onscreen (MetaRendererNative   *renderer_native,
 
   /* We have wait_for_pending_flips hardcoded, so throttling always. */
   cogl_onscreen_set_swap_throttled (onscreen, TRUE);
-  if (!_clutter_get_sync_to_vblank ())
-    g_warning ("Request to disable sync-to-vblank is being ignored. "
-               "MetaRendererNative does not support disabling it.");
 
   if (!cogl_framebuffer_allocate (COGL_FRAMEBUFFER (onscreen), error))
     {