[mutter/wip/carlosg/xwayland-startup-side-channel: 1/3] xwayland: Allow setting up maintenance processes

[Carlos Garnacho <carlosg src gnome org>]

commit aba7f0d9dbf18b71c9471f1d96cbd9713c862cd6
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Jul 20 00:22:13 2019 +0200

    xwayland: Allow setting up maintenance processes
    
    This is made a signal, so the upper layers (read: gnome-shell) may
    decide what services to spawn. The signal argument contains a task
    that will resume X11 startup after it is returned upon.

 src/core/display.c          |  9 +++++++++
 src/wayland/meta-xwayland.c | 29 +++++++++++++++++++++++++++--
 2 files changed, 36 insertions(+), 2 deletions(-)
---
diff --git a/src/core/display.c b/src/core/display.c
index b18f5a558..fb797ab05 100644
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -157,6 +157,7 @@ enum
   RESTACKED,
   WORKAREAS_CHANGED,
   CLOSING,
+  INIT_XSERVER,
   LAST_SIGNAL
 };
 
@@ -501,6 +502,14 @@ meta_display_class_init (MetaDisplayClass *klass)
                   0, NULL, NULL, NULL,
                   G_TYPE_NONE, 0);
 
+  display_signals[INIT_XSERVER] =
+    g_signal_new ("init-xserver",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  0, g_signal_accumulator_first_wins,
+                  NULL, NULL,
+                  G_TYPE_BOOLEAN, 1, G_TYPE_TASK);
+
   g_object_class_install_property (object_class,
                                    PROP_FOCUS_WINDOW,
                                    g_param_spec_object ("focus-window",
diff --git a/src/wayland/meta-xwayland.c b/src/wayland/meta-xwayland.c
index ed11e37b0..85fa18a19 100644
--- a/src/wayland/meta-xwayland.c
+++ b/src/wayland/meta-xwayland.c
@@ -608,6 +608,19 @@ xserver_finished_init (MetaXWaylandManager *manager)
   g_clear_pointer (&manager->init_loop, g_main_loop_unref);
 }
 
+static void
+init_xserver_cb (MetaDisplay  *display,
+                 GTask        *task,
+                 gpointer      user_data)
+{
+  if (!g_task_propagate_boolean (task, NULL))
+    g_warning ("Could not initialize Xwayland services");
+
+  /* Create the X11 display despite the Xwayland services' state */
+  if (meta_get_x11_display_policy () == META_DISPLAY_POLICY_ON_DEMAND)
+    meta_display_init_x11 (display, NULL);
+}
+
 static gboolean
 on_displayfd_ready (int          fd,
                     GIOCondition condition,
@@ -615,6 +628,8 @@ on_displayfd_ready (int          fd,
 {
   MetaXWaylandManager *manager = user_data;
   MetaDisplay *display = meta_get_display ();
+  GTask *task;
+  gboolean retval;
 
   /* The server writes its display name to the displayfd
    * socket when it's ready. We don't care about the data
@@ -622,8 +637,18 @@ on_displayfd_ready (int          fd,
    * that means it's ready. */
   xserver_finished_init (manager);
 
-  if (meta_get_x11_display_policy () == META_DISPLAY_POLICY_ON_DEMAND)
-    meta_display_init_x11 (display, NULL);
+  task = g_task_new (display, NULL,
+                     (GAsyncReadyCallback) init_xserver_cb,
+                     display);
+  g_signal_emit_by_name (display, "init-xserver", task, &retval);
+
+  if (!retval)
+    {
+      /* No handlers for this signal, proceed right away */
+      g_task_return_boolean (task, TRUE);
+    }
+
+  g_object_unref (task);
 
   return G_SOURCE_REMOVE;
 }