core: Make meta_display_init_x11() an async function

This ATM completes the task right away, but we will want to do
further things here that are asynchronous in nature, so prepare
for this operation being async.

Since the X11 backend doesn't really need this, make it go on
the fast lane and open the MetaX11Display right away, the case
of mandatory Xwayland on a wayland session is now handled
separately.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/944

src/core/display-private.h

@@ -426,8 +426,14 @@ MetaWindow *meta_display_get_window_from_id (MetaDisplay *display,
                                              uint64_t     window_id);
 uint64_t    meta_display_generate_window_id (MetaDisplay *display);
 
-gboolean meta_display_init_x11     (MetaDisplay  *display,
+void meta_display_init_x11 (MetaDisplay         *display,
+                            GCancellable        *cancellable,
+                            GAsyncReadyCallback  callback,
+                            gpointer             user_data);
+gboolean meta_display_init_x11_finish (MetaDisplay   *display,
+                                       GAsyncResult  *result,
                                        GError       **error);
+
 void     meta_display_shutdown_x11 (MetaDisplay  *display);
 
 #endif

src/core/display.c

@@ -656,13 +656,45 @@ on_ui_scaling_factor_changed (MetaSettings *settings,
   meta_display_reload_cursor (display);
 }
 
-gboolean
-meta_display_init_x11 (MetaDisplay  *display,
+static gboolean
+meta_display_init_x11_display (MetaDisplay  *display,
                                GError      **error)
 {
   MetaX11Display *x11_display;
 
-  g_assert (display->x11_display == NULL);
+  x11_display = meta_x11_display_new (display, error);
+  if (!x11_display)
+    return FALSE;
+
+  display->x11_display = x11_display;
+  g_signal_emit (display, display_signals[X11_DISPLAY_SETUP], 0);
+
+  meta_x11_display_create_guard_window (x11_display);
+
+  if (!display->display_opening)
+    {
+      g_signal_emit (display, display_signals[X11_DISPLAY_OPENED], 0);
+      meta_display_manage_all_xwindows (display);
+      meta_compositor_redirect_x11_windows (display->compositor);
+    }
+
+  return TRUE;
+}
+
+#ifdef HAVE_WAYLAND
+gboolean
+meta_display_init_x11_finish (MetaDisplay   *display,
+                              GAsyncResult  *result,
+                              GError       **error)
+{
+  MetaX11Display *x11_display;
+
+  g_assert (g_task_get_source_tag (G_TASK (result)) == meta_display_init_x11);
+
+  if (!g_task_propagate_boolean (G_TASK (result), error))
+    return FALSE;
+  if (display->x11_display)
+    return TRUE;
 
   x11_display = meta_x11_display_new (display, error);
   if (!x11_display)
@@ -684,6 +716,31 @@ meta_display_init_x11 (MetaDisplay  *display,
   return TRUE;
 }
 
+void
+meta_display_init_x11 (MetaDisplay         *display,
+                       GCancellable        *cancellable,
+                       GAsyncReadyCallback  callback,
+                       gpointer             user_data)
+{
+  GTask *task;
+
+  task = g_task_new (display, cancellable, callback, user_data);
+  g_task_set_source_tag (task, meta_display_init_x11);
+
+  g_task_return_boolean (task, TRUE);
+  g_object_unref (task);
+}
+
+static void
+on_x11_initialized (MetaDisplay  *display,
+                    GAsyncResult *result,
+                    gpointer      user_data)
+{
+  if (!meta_display_init_x11_finish (display, result, NULL))
+    g_critical ("Failed to init X11 display");
+}
+#endif
+
 void
 meta_display_shutdown_x11 (MetaDisplay *display)
 {
@@ -791,16 +848,25 @@ meta_display_open (void)
   display->selection = meta_selection_new (display);
   meta_clipboard_manager_init (display);
 
+#ifdef HAVE_WAYLAND
+  if (meta_is_wayland_compositor ())
+    {
       if (meta_get_x11_display_policy () == META_DISPLAY_POLICY_MANDATORY)
         {
-      if (!meta_display_init_x11 (display, &error))
-        g_error ("Failed to start Xwayland: %s", error->message);
+          meta_display_init_x11 (display, NULL,
+                                 (GAsyncReadyCallback) on_x11_initialized,
+                                 NULL);
+        }
 
-      timestamp = display->x11_display->timestamp;
+      timestamp = meta_display_get_current_time_roundtrip (display);
     }
   else
+#endif
     {
-      timestamp = meta_display_get_current_time_roundtrip (display);
+      if (!meta_display_init_x11_display (display, &error))
+        g_error ("Failed to init X11 display: %s", error->message);
+
+      timestamp = display->x11_display->timestamp;
     }
 
   display->last_focus_time = timestamp;

src/wayland/meta-xwayland.c

@@ -545,6 +545,17 @@ xserver_finished_init (MetaXWaylandManager *manager)
   g_clear_pointer (&manager->init_loop, g_main_loop_unref);
 }
 
+static void
+on_init_x11_cb (MetaDisplay  *display,
+                GAsyncResult *result,
+                gpointer      user_data)
+{
+  g_autoptr (GError) error = NULL;
+
+  if (!meta_display_init_x11_finish (display, result, &error))
+    g_warning ("Failed to initialize X11 display: %s\n", error->message);
+}
+
 static gboolean
 on_displayfd_ready (int          fd,
                     GIOCondition condition,
@@ -560,7 +571,10 @@ on_displayfd_ready (int          fd,
   xserver_finished_init (manager);
 
   if (meta_get_x11_display_policy () == META_DISPLAY_POLICY_ON_DEMAND)
-    meta_display_init_x11 (display, NULL);
+    {
+      meta_display_init_x11 (display, NULL,
+                             (GAsyncReadyCallback) on_init_x11_cb, NULL);
+    }
 
   return G_SOURCE_REMOVE;
 }