backend: Freeze frame clock when headless

Don't schedule redraws when being headless; there is nothing to draw so
don't attempt to draw. This also makes a flaky test become non-flaky, as
it previously spuriously got warnings due to windows being "painted"
when headless but lacking frame timings, as nothing was actually
painted.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/170

1 files changed, 15 insertions, 0 deletions

diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c
index 375e9d298..709d4194c 100644
--- a/src/backends/meta-backend.c
+++ b/src/backends/meta-backend.c
@@ -123,6 +123,8 @@ struct _MetaBackendPrivate
   guint sleep_signal_id;
   GCancellable *cancellable;
   GDBusConnection *system_bus;
+
+  gboolean was_headless;
 };
 typedef struct _MetaBackendPrivate MetaBackendPrivate;
 
@@ -223,6 +225,19 @@ meta_backend_monitors_changed (MetaBackend *backend)
     }
 
   meta_cursor_renderer_force_update (priv->cursor_renderer);
+
+  if (meta_monitor_manager_is_headless (priv->monitor_manager) &&
+      !priv->was_headless)
+    {
+      clutter_stage_freeze_updates (CLUTTER_STAGE (priv->stage));
+      priv->was_headless = TRUE;
+    }
+  else if (!meta_monitor_manager_is_headless (priv->monitor_manager) &&
+           priv->was_headless)
+    {
+      clutter_stage_thaw_updates (CLUTTER_STAGE (priv->stage));
+      priv->was_headless = FALSE;
+    }
 }
 
 void