[mutter] monitor: Unset output monitor when disposing

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

commit 47a67252078ba5c78ec5e17dae5e32bf91c8da08
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Jan 27 23:16:05 2021 +0100

    monitor: Unset output monitor when disposing
    
    When rebuilding the monitors (e.g. during hotplug), make sure to detach
    the disposed monitors from any outputs before creating the new monitors.
    While this isn't currently needed, as outputs are too being recreated,
    with the to be introduced virtual outputs that are created for virtual
    monitors, this is not always the case anymore, as these virtual outputs
    are not regenerated each time anything changes.
    
    Prepare for this by making sure that cleaning up disposed monitors
    detach themself properly from the outputs, so new ones can attach
    themself to outputs without running into conflicts.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>

 src/backends/meta-monitor-manager.c |  9 ++++++++-
 src/backends/meta-monitor.c         |  1 +
 src/backends/meta-output.c          | 10 ++++++++++
 src/backends/meta-output.h          |  2 ++
 4 files changed, 21 insertions(+), 1 deletion(-)
---
diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index 620b60d0a6..8744d729e8 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -2843,6 +2843,13 @@ meta_monitor_manager_get_power_save_mode (MetaMonitorManager *manager)
   return priv->power_save_mode;
 }
 
+static void
+destroy_monitor (MetaMonitor *monitor)
+{
+  g_object_run_dispose (G_OBJECT (monitor));
+  g_object_unref (monitor);
+}
+
 static void
 rebuild_monitors (MetaMonitorManager *manager)
 {
@@ -2851,7 +2858,7 @@ rebuild_monitors (MetaMonitorManager *manager)
 
   if (manager->monitors)
     {
-      g_list_free_full (manager->monitors, g_object_unref);
+      g_list_free_full (manager->monitors, (GDestroyNotify) destroy_monitor);
       manager->monitors = NULL;
     }
 
diff --git a/src/backends/meta-monitor.c b/src/backends/meta-monitor.c
index 8f147b70c2..e02f8ed459 100644
--- a/src/backends/meta-monitor.c
+++ b/src/backends/meta-monitor.c
@@ -486,6 +486,7 @@ meta_monitor_dispose (GObject *object)
 
   if (priv->outputs)
     {
+      g_list_foreach (priv->outputs, (GFunc) meta_output_unset_monitor, NULL);
       g_list_free_full (priv->outputs, g_object_unref);
       priv->outputs = NULL;
     }
diff --git a/src/backends/meta-output.c b/src/backends/meta-output.c
index c903110a65..432697d6d9 100644
--- a/src/backends/meta-output.c
+++ b/src/backends/meta-output.c
@@ -135,6 +135,16 @@ meta_output_set_monitor (MetaOutput  *output,
   priv->monitor = monitor;
 }
 
+void
+meta_output_unset_monitor (MetaOutput *output)
+{
+  MetaOutputPrivate *priv = meta_output_get_instance_private (output);
+
+  g_warn_if_fail (priv->monitor);
+
+  priv->monitor = NULL;
+}
+
 const char *
 meta_output_get_name (MetaOutput *output)
 {
diff --git a/src/backends/meta-output.h b/src/backends/meta-output.h
index bed1996626..3c4431c4d9 100644
--- a/src/backends/meta-output.h
+++ b/src/backends/meta-output.h
@@ -145,6 +145,8 @@ MetaMonitor * meta_output_get_monitor (MetaOutput *output);
 void meta_output_set_monitor (MetaOutput  *output,
                               MetaMonitor *monitor);
 
+void meta_output_unset_monitor (MetaOutput *output);
+
 const char * meta_output_get_name (MetaOutput *output);
 
 META_EXPORT_TEST