[mutter] screen-cast/monitor-stream: Don't fall apart when monitor changes

[Marge Bot <marge-bot src gnome org>]

commit e877b06fdde60a9fc391628c83258e4ee3b42297
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Jan 27 23:25:51 2021 +0100

    screen-cast/monitor-stream: Don't fall apart when monitor changes
    
    If the monitor configuration changed, even though the streamed monitor
    didn't change, we'd still fail to continue streaming, as we failed to
    update the stage watchers, meaning we wouldn't be notified about when
    the stage views were painted.
    
    Fix this by reattaching the stage watches, i.e. update the painted
    signalling listeners to listen to the right views, when monitor changes
    happens.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1691>

 src/backends/meta-screen-cast-monitor-stream-src.c | 63 +++++++++++++++++-----
 1 file changed, 50 insertions(+), 13 deletions(-)
---
diff --git a/src/backends/meta-screen-cast-monitor-stream-src.c 
b/src/backends/meta-screen-cast-monitor-stream-src.c
index e227182668..2fa7ebdef2 100644
--- a/src/backends/meta-screen-cast-monitor-stream-src.c
+++ b/src/backends/meta-screen-cast-monitor-stream-src.c
@@ -323,18 +323,59 @@ add_view_watches (MetaScreenCastMonitorStreamSrc *monitor_src,
     }
 }
 
+static void
+reattach_watches (MetaScreenCastMonitorStreamSrc *monitor_src)
+{
+  MetaScreenCastStreamSrc *src = META_SCREEN_CAST_STREAM_SRC (monitor_src);
+  MetaScreenCastStream *stream;
+  ClutterStage *stage;
+  GList *l;
+
+  stream = meta_screen_cast_stream_src_get_stream (src);
+  stage = get_stage (monitor_src);
+
+  for (l = monitor_src->watches; l; l = l->next)
+    meta_stage_remove_watch (META_STAGE (stage), l->data);
+  g_clear_pointer (&monitor_src->watches, g_list_free);
+
+  switch (meta_screen_cast_stream_get_cursor_mode (stream))
+    {
+    case META_SCREEN_CAST_CURSOR_MODE_METADATA:
+    case META_SCREEN_CAST_CURSOR_MODE_HIDDEN:
+      add_view_watches (monitor_src,
+                        META_STAGE_WATCH_BEFORE_PAINT,
+                        before_stage_painted);
+      add_view_watches (monitor_src,
+                        META_STAGE_WATCH_AFTER_ACTOR_PAINT,
+                        stage_painted);
+      break;
+    case META_SCREEN_CAST_CURSOR_MODE_EMBEDDED:
+      add_view_watches (monitor_src,
+                        META_STAGE_WATCH_AFTER_PAINT,
+                        stage_painted);
+      break;
+    }
+}
+
+static void
+on_monitors_changed (MetaMonitorManager             *monitor_manager,
+                     MetaScreenCastMonitorStreamSrc *monitor_src)
+{
+  reattach_watches (monitor_src);
+}
+
 static void
 meta_screen_cast_monitor_stream_src_enable (MetaScreenCastStreamSrc *src)
 {
   MetaScreenCastMonitorStreamSrc *monitor_src =
     META_SCREEN_CAST_MONITOR_STREAM_SRC (src);
   MetaBackend *backend = get_backend (monitor_src);
+  MetaMonitorManager *monitor_manager =
+    meta_backend_get_monitor_manager (backend);
   MetaCursorTracker *cursor_tracker = meta_backend_get_cursor_tracker (backend);
-  ClutterStage *stage;
   MetaScreenCastStream *stream;
 
   stream = meta_screen_cast_stream_src_get_stream (src);
-  stage = get_stage (monitor_src);
 
   switch (meta_screen_cast_stream_get_cursor_mode (stream))
     {
@@ -348,25 +389,21 @@ meta_screen_cast_monitor_stream_src_enable (MetaScreenCastStreamSrc *src)
                                 G_CALLBACK (cursor_changed),
                                 monitor_src);
       meta_cursor_tracker_track_position (cursor_tracker);
-      G_GNUC_FALLTHROUGH;
+      break;
     case META_SCREEN_CAST_CURSOR_MODE_HIDDEN:
-      add_view_watches (monitor_src,
-                        META_STAGE_WATCH_BEFORE_PAINT,
-                        before_stage_painted);
-      add_view_watches (monitor_src,
-                        META_STAGE_WATCH_AFTER_ACTOR_PAINT,
-                        stage_painted);
       break;
     case META_SCREEN_CAST_CURSOR_MODE_EMBEDDED:
       inhibit_hw_cursor (monitor_src);
       meta_cursor_tracker_track_position (cursor_tracker);
-      add_view_watches (monitor_src,
-                        META_STAGE_WATCH_AFTER_PAINT,
-                        stage_painted);
       break;
     }
 
-  clutter_actor_queue_redraw (CLUTTER_ACTOR (stage));
+  reattach_watches (monitor_src);
+  g_signal_connect_object (monitor_manager, "monitors-changed-internal",
+                           G_CALLBACK (on_monitors_changed),
+                           monitor_src, 0);
+
+  clutter_actor_queue_redraw (CLUTTER_ACTOR (get_stage (monitor_src)));
 }
 
 static void