[mutter] compositor/plugin-manager: Split start() from new()

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

commit 5b720a157cfa71ae855d8206b4a6eeb3cdf18eec
Author: Florian Müllner <fmuellner gnome org>
Date:   Tue Jan 18 19:25:57 2022 +0100

    compositor/plugin-manager: Split start() from new()
    
    In order to support dynamic imports, gjs added an implicit mainloop
    that can drive the main context independently from other mainloops
    like the one from GApplication or MetaContext.
    
    That means that sources can now get dispatched to the main context
    from the moment the plugin is started, resulting in a crash as the
    association between compositor and plugin manager doesn't exist until
    meta_plugin_manager_new() returns.
    
    Make sure this doesn't happen by only starting the plugin after
    meta_plugin_manager_new() has returned.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2242>

 src/compositor/compositor.c          |  1 +
 src/compositor/meta-plugin-manager.c | 16 ++++++++++------
 src/compositor/meta-plugin-manager.h |  2 ++
 3 files changed, 13 insertions(+), 6 deletions(-)
---
diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index ee6be007b8..7d14068fdf 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -548,6 +548,7 @@ meta_compositor_do_manage (MetaCompositor  *compositor,
     return FALSE;
 
   priv->plugin_mgr = meta_plugin_manager_new (compositor);
+  meta_plugin_manager_start (priv->plugin_mgr);
 
   return TRUE;
 }
diff --git a/src/compositor/meta-plugin-manager.c b/src/compositor/meta-plugin-manager.c
index ab7fce663d..94d62c2126 100644
--- a/src/compositor/meta-plugin-manager.c
+++ b/src/compositor/meta-plugin-manager.c
@@ -97,7 +97,6 @@ MetaPluginManager *
 meta_plugin_manager_new (MetaCompositor *compositor)
 {
   MetaPluginManager *plugin_mgr;
-  MetaPluginClass *klass;
   MetaPlugin *plugin;
   MetaMonitorManager *monitors;
 
@@ -107,11 +106,6 @@ meta_plugin_manager_new (MetaCompositor *compositor)
 
   _meta_plugin_set_compositor (plugin, compositor);
 
-  klass = META_PLUGIN_GET_CLASS (plugin);
-
-  if (klass->start)
-    klass->start (plugin);
-
   monitors = meta_monitor_manager_get ();
   g_signal_connect (monitors, "confirm-display-change",
                     G_CALLBACK (on_confirm_display_change), plugin_mgr);
@@ -119,6 +113,16 @@ meta_plugin_manager_new (MetaCompositor *compositor)
   return plugin_mgr;
 }
 
+void
+meta_plugin_manager_start (MetaPluginManager *plugin_mgr)
+{
+  MetaPlugin *plugin = plugin_mgr->plugin;
+  MetaPluginClass *klass = META_PLUGIN_GET_CLASS (plugin);
+
+  if (klass->start)
+    klass->start (plugin);
+}
+
 static void
 meta_plugin_manager_kill_window_effects (MetaPluginManager *plugin_mgr,
                                          MetaWindowActor   *actor)
diff --git a/src/compositor/meta-plugin-manager.h b/src/compositor/meta-plugin-manager.h
index d1c007fa19..a5fe0315ab 100644
--- a/src/compositor/meta-plugin-manager.h
+++ b/src/compositor/meta-plugin-manager.h
@@ -45,6 +45,8 @@ typedef struct MetaPluginManager MetaPluginManager;
 
 MetaPluginManager * meta_plugin_manager_new (MetaCompositor *compositor);
 
+void meta_plugin_manager_start (MetaPluginManager *plugin_mgr);
+
 META_EXPORT_TEST
 void     meta_plugin_manager_load         (const gchar       *plugin_name);