output: Tie the output to the monitor it's part of

Outputs correspond to active connectors, that we translate into
monitors. Make this association more real by adding a pointer back to
the monitor from the output.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>

src/backends/meta-monitor.c

@@ -675,6 +675,8 @@ meta_monitor_normal_new (MetaGpu            *gpu,
   monitor_priv->gpu = gpu;
 
   monitor_priv->outputs = g_list_append (NULL, g_object_ref (output));
+  meta_output_set_monitor (output, monitor);
+
   monitor_priv->winsys_id = meta_output_get_id (output);
   meta_monitor_generate_spec (monitor);
 
@@ -802,6 +804,8 @@ add_tiled_monitor_outputs (MetaGpu          *gpu,
 
       monitor_priv->outputs = g_list_append (monitor_priv->outputs,
                                              g_object_ref (output));
+
+      meta_output_set_monitor (output, META_MONITOR (monitor_tiled));
     }
 }
 

src/backends/meta-output.c

@@ -45,6 +45,8 @@ typedef struct _MetaOutputPrivate
 
   MetaOutputInfo *info;
 
+  MetaMonitor *monitor;
+
   /* The CRTC driving this output, NULL if the output is not enabled */
   MetaCrtc *crtc;
 
@@ -112,6 +114,27 @@ meta_output_get_gpu (MetaOutput *output)
   return priv->gpu;
 }
 
+MetaMonitor *
+meta_output_get_monitor (MetaOutput *output)
+{
+  MetaOutputPrivate *priv = meta_output_get_instance_private (output);
+
+  g_warn_if_fail (priv->monitor);
+
+  return priv->monitor;
+}
+
+void
+meta_output_set_monitor (MetaOutput  *output,
+                         MetaMonitor *monitor)
+{
+  MetaOutputPrivate *priv = meta_output_get_instance_private (output);
+
+  g_warn_if_fail (!priv->monitor);
+
+  priv->monitor = monitor;
+}
+
 const char *
 meta_output_get_name (MetaOutput *output)
 {

src/backends/meta-output.h

@@ -139,6 +139,12 @@ uint64_t meta_output_get_id (MetaOutput *output);
 META_EXPORT_TEST
 MetaGpu * meta_output_get_gpu (MetaOutput *output);
 
+META_EXPORT_TEST
+MetaMonitor * meta_output_get_monitor (MetaOutput *output);
+
+void meta_output_set_monitor (MetaOutput  *output,
+                              MetaMonitor *monitor);
+
 const char * meta_output_get_name (MetaOutput *output);
 
 META_EXPORT_TEST

src/tests/monitor-test-utils.c

@@ -289,6 +289,8 @@ check_logical_monitor (MetaMonitorManager             *monitor_manager,
           MetaOutput *output = l_output->data;
           MetaCrtc *crtc;
 
+          g_assert (meta_output_get_monitor (output) == monitor);
+
           if (meta_output_is_primary (output))
             {
               g_assert_null (primary_output);