[mutter] renderer-native: Advertise _FEATURE_SWAP_THROTTLE

[Jonas Ådahl <jadahl src gnome org>]

commit e8c27603dd69d94793aed5e0525562669e8c0bca
Author: Daniel van Vugt <daniel van vugt canonical com>
Date:   Tue Jul 10 17:46:02 2018 +0800

    renderer-native: Advertise _FEATURE_SWAP_THROTTLE
    
    Because it is implemented and always on. By advertising this fact
    the master clock is able to sync to the native refresh rate instead
    of always using the fallback of 60.00Hz.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=781296

 src/backends/native/meta-renderer-native.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)
---
diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index 768c70e1c..96afdc4d1 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -2082,6 +2082,13 @@ meta_renderer_native_init_egl_context (CoglContext *cogl_context,
                   COGL_WINSYS_FEATURE_MULTIPLE_ONSCREEN,
                   TRUE);
 
+  /* COGL_WINSYS_FEATURE_SWAP_THROTTLE is always true for this renderer
+   * because we have the call to wait_for_pending_flips on every frame.
+   */
+  COGL_FLAGS_SET (cogl_context->winsys_features,
+                  COGL_WINSYS_FEATURE_SWAP_THROTTLE,
+                  TRUE);
+
 #ifdef HAVE_EGL_DEVICE
   if (renderer_gpu_data->mode == META_RENDERER_NATIVE_MODE_EGL_DEVICE)
     COGL_FLAGS_SET (cogl_context->features,
@@ -2717,8 +2724,12 @@ meta_renderer_native_create_onscreen (MetaRendererNative   *renderer_native,
     }
 
   onscreen = cogl_onscreen_new (context, width, height);
-  cogl_onscreen_set_swap_throttled (onscreen,
-                                    _clutter_get_sync_to_vblank ());
+
+  /* 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))
     {