From d7b87799c84099ccce60840a2271b882e05cac24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20=C3=85dahl?= <jadahl@gmail.com>
Date: Wed, 6 Jul 2016 15:27:45 +0800
Subject: [PATCH] backend: Ensure the backend gets notified of monitor state
 having changed

Being a listener to a signal, it is inconvenient to enforce order of
execution between different signal listeners. If there are things in
the backend that should be updated before various other signal
handlers, make sure so is done by emitting the signal after having
explicitly notified the backend.

https://bugzilla.gnome.org/show_bug.cgi?id=768976
---
 src/backends/meta-backend-private.h |  2 ++
 src/backends/meta-backend.c         | 13 ++++++-------
 src/backends/meta-monitor-manager.c |  8 ++++++++
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/backends/meta-backend-private.h b/src/backends/meta-backend-private.h
index 08b249924..5c65ff969 100644
--- a/src/backends/meta-backend-private.h
+++ b/src/backends/meta-backend-private.h
@@ -142,4 +142,6 @@ void meta_backend_set_client_pointer_constraint (MetaBackend *backend,
 
 ClutterBackend * meta_backend_get_clutter_backend (MetaBackend *backend);
 
+void meta_backend_monitors_changed (MetaBackend *backend);
+
 #endif /* META_BACKEND_PRIVATE_H */
diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c
index 2ad6b8445..1889fdb94 100644
--- a/src/backends/meta-backend.c
+++ b/src/backends/meta-backend.c
@@ -116,11 +116,11 @@ center_pointer (MetaBackend *backend)
                              primary->rect.y + primary->rect.height / 2);
 }
 
-static void
-on_monitors_changed (MetaMonitorManager *monitors,
-                     gpointer user_data)
+void
+meta_backend_monitors_changed (MetaBackend *backend)
 {
-  MetaBackend *backend = META_BACKEND (user_data);
+  MetaMonitorManager *monitor_manager =
+    meta_backend_get_monitor_manager (backend);
   ClutterDeviceManager *manager = clutter_device_manager_get_default ();
   ClutterInputDevice *device = clutter_device_manager_get_core_device (manager, CLUTTER_POINTER_DEVICE);
   ClutterPoint point;
@@ -130,7 +130,8 @@ on_monitors_changed (MetaMonitorManager *monitors,
   if (clutter_input_device_get_coords (device, NULL, &point))
     {
       /* If we're outside all monitors, warp the pointer back inside */
-      if (meta_monitor_manager_get_monitor_at_point (monitors, point.x, point.y) < 0)
+      if (meta_monitor_manager_get_monitor_at_point (monitor_manager,
+                                                     point.x, point.y) < 0)
         center_pointer (backend);
     }
 }
@@ -278,8 +279,6 @@ meta_backend_real_post_init (MetaBackend *backend)
 
   priv->monitor_manager = create_monitor_manager (backend);
 
-  g_signal_connect (priv->monitor_manager, "monitors-changed",
-                    G_CALLBACK (on_monitors_changed), backend);
   meta_backend_sync_screen_size (backend);
 
   priv->cursor_renderer = META_BACKEND_GET_CLASS (backend)->create_cursor_renderer (backend);
diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index e00d3cedd..8fb79fc61 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -1379,6 +1379,7 @@ meta_monitor_manager_read_current_config (MetaMonitorManager *manager)
 void
 meta_monitor_manager_rebuild_derived (MetaMonitorManager *manager)
 {
+  MetaBackend *backend = meta_get_backend ();
   MetaMonitorManagerClass *manager_class = META_MONITOR_MANAGER_GET_CLASS (manager);
   MetaMonitorInfo *old_monitor_infos;
   unsigned old_n_monitor_infos;
@@ -1408,6 +1409,13 @@ meta_monitor_manager_rebuild_derived (MetaMonitorManager *manager)
             manager_class->delete_monitor (manager, old_monitor_infos[i].monitor_winsys_xid);
         }
     }
+
+  /* Tell the backend about that the monitors changed before emitting the
+   * signal, so that the backend can prepare itself before all the signal
+   * consumers.
+   */
+  meta_backend_monitors_changed (backend);
+
   g_signal_emit_by_name (manager, "monitors-changed");
 
   g_free (old_monitor_infos);