[gnome-shell] shell/tray-manager: Delay managing screen if necessary

[Florian Müllner <fmuellner src gnome org>]

commit 4ff94f80a00d0e1e0a9e48df5c390cdf98a476b3
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Mar 4 14:27:54 2020 +0100

    shell/tray-manager: Delay managing screen if necessary
    
    Now that Xwayland startup is asynchronous, the function may be called
    before X11 is available, resulting in a crash.
    
    Fix this by only managing the tray immediately if we already have an
    X11 display, and wait for it to be set up otherwise.
    
    Likewise, unmanage the screen when X11 becomes unavailable.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/issues/2308

 src/shell-tray-manager.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)
---
diff --git a/src/shell-tray-manager.c b/src/shell-tray-manager.c
index ea7066be67..e23179f4ed 100644
--- a/src/shell-tray-manager.c
+++ b/src/shell-tray-manager.c
@@ -218,6 +218,9 @@ shell_tray_manager_style_changed (StWidget *theme_widget,
   StThemeNode *theme_node;
   StIconColors *icon_colors;
 
+  if (manager->priv->na_manager == NULL)
+    return;
+
   theme_node = st_widget_get_theme_node (theme_widget);
   icon_colors = st_theme_node_get_icon_colors (theme_node);
   na_tray_manager_set_colors (manager->priv->na_manager,
@@ -225,15 +228,30 @@ shell_tray_manager_style_changed (StWidget *theme_widget,
                               &icon_colors->error, &icon_colors->success);
 }
 
+static void
+shell_tray_manager_manage_screen_internal (ShellTrayManager *manager)
+{
+  shell_tray_manager_ensure_resources (manager);
+  na_tray_manager_manage_screen (manager->priv->na_manager);
+}
+
 void
 shell_tray_manager_manage_screen (ShellTrayManager *manager,
                                   StWidget         *theme_widget)
 {
+  MetaDisplay *display = shell_global_get_display (shell_global_get ());
+
   g_set_weak_pointer (&manager->priv->theme_widget, theme_widget);
 
-  shell_tray_manager_ensure_resources (manager);
+  if (meta_display_get_x11_display (display) != NULL)
+    shell_tray_manager_manage_screen_internal (manager);
 
-  na_tray_manager_manage_screen (manager->priv->na_manager);
+  g_signal_connect_object (display, "x11-display-setup",
+                           G_CALLBACK (shell_tray_manager_manage_screen_internal),
+                           manager, G_CONNECT_SWAPPED);
+  g_signal_connect_object (display, "x11-display-closing",
+                           G_CALLBACK (shell_tray_manager_release_resources),
+                           manager, G_CONNECT_SWAPPED);
 
   g_signal_connect_object (theme_widget, "style-changed",
                            G_CALLBACK (shell_tray_manager_style_changed),
@@ -244,6 +262,10 @@ shell_tray_manager_manage_screen (ShellTrayManager *manager,
 void
 shell_tray_manager_unmanage_screen (ShellTrayManager *manager)
 {
+  MetaDisplay *display = shell_global_get_display (shell_global_get ());
+
+  g_signal_handlers_disconnect_by_data (display, manager);
+
   if (manager->priv->theme_widget != NULL)
     {
       g_signal_handlers_disconnect_by_func (manager->priv->theme_widget,