xwayland: Use Xwayland auto-terminate feature

When using Xwayland-on-demand (default), if the (experimental) autoclose
features is enabled, we can rely on Xwayland's auto-terminate feature
instead of explicitly killing the Xwayland process.

With it, gone is the mechanism that was added to check the X11 clients
connected and their executable to check whether we can (safely) kill
Xwayland.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1794>

config.h.meson

@@ -89,8 +89,5 @@
 /* Whether the memfd_create function exists */
 #mesondefine HAVE_MEMFD_CREATE
 
-/* List of executable names to ignore when terminating Xwayland */
-#mesondefine XWAYLAND_IGNORE_EXECUTABLES
-
 /* Whether the Xwayland -terminate supports a delay */
 #mesondefine HAVE_XWAYLAND_TERMINATE_DELAY

data/org.gnome.mutter.gschema.xml.in

@@ -145,8 +145,8 @@
                                         everything else. Requires a restart.
 
         • “autoclose-xwayland”        — automatically terminates Xwayland if all
-                                        relevant X11 clients are gone. Does not
-                                        require a restart.
+                                        relevant X11 clients are gone.
+                                        Requires a restart.
 
       </description>
     </key>

meson.build

@@ -546,10 +546,6 @@ xwayland_grab_default_access_rules = get_option('xwayland_grab_default_access_ru
 cdata.set_quoted('XWAYLAND_GRAB_DEFAULT_ACCESS_RULES',
                  xwayland_grab_default_access_rules)
 
-xwayland_ignore_executables = get_option('xwayland_ignore_executables')
-cdata.set_quoted('XWAYLAND_IGNORE_EXECUTABLES',
-                 xwayland_ignore_executables)
-
 cdata.set_quoted('MUTTER_PLUGIN_DIR', join_paths(pkglibdir, 'plugins'))
 cdata.set_quoted('MUTTER_LOCALEDIR', localedir)
 cdata.set_quoted('MUTTER_LIBEXECDIR', libexecdir)

meson_options.txt

@@ -200,9 +200,3 @@ option('xwayland_initfd',
   value: 'auto',
   description: 'Whether -initfd argument is passed to Xwayland to guarantee services (e.g. gsd-xsettings) startup before applications'
 )
-
-option('xwayland_ignore_executables',
-  type: 'string',
-  value: 'gsd-xsettings,ibus-x11,pulseaudio,Xwayland',
-  description: 'Comma delimited list of executable names to ignore when terminating Xwayland'
-)

src/wayland/meta-xwayland.c

@@ -139,146 +139,6 @@ meta_xwayland_is_xwayland_surface (MetaWaylandSurface *surface)
   return wl_resource_get_client (surface->resource) == manager->client;
 }
 
-static char *
-meta_xwayland_get_exe_from_proc_entry (const char *proc_entry)
-{
-  g_autofree char *exepath = NULL;
-  char *executable;
-  char *p;
-
-  exepath = g_file_read_link (proc_entry, NULL);
-  if (!exepath)
-    return NULL;
-
-  p = strrchr (exepath, G_DIR_SEPARATOR);
-  if (p)
-    executable = g_strdup (++p);
-  else
-    executable = g_strdup (exepath);
-
-  return executable;
-}
-
-static char *
-meta_xwayland_get_exe_from_pid (uint32_t pid)
-{
-  g_autofree char *proc_entry = NULL;
-  char *executable;
-
-  proc_entry = g_strdup_printf ("/proc/%i/exe", pid);
-  executable = meta_xwayland_get_exe_from_proc_entry (proc_entry);
-
-  return executable;
-}
-
-static char *
-meta_xwayland_get_self_exe (void)
-{
-  g_autofree char *proc_entry = NULL;
-  char *executable;
-
-  proc_entry = g_strdup_printf ("/proc/self/exe");
-  executable = meta_xwayland_get_exe_from_proc_entry (proc_entry);
-
-  return executable;
-}
-
-static gboolean
-can_xwayland_ignore_exe (const char *executable,
-                         const char *self)
-{
-  char ** ignore_executables;
-  gboolean ret;
-
-  if (!g_strcmp0 (executable, self))
-    return TRUE;
-
-  ignore_executables = g_strsplit_set (XWAYLAND_IGNORE_EXECUTABLES, ",", -1);
-  ret = g_strv_contains ((const char * const *) ignore_executables, executable);
-  g_strfreev (ignore_executables);
-
-  return ret;
-}
-
-static uint32_t
-meta_xwayland_get_client_pid (xcb_connection_t *xcb,
-                              uint32_t          client)
-{
-  xcb_res_client_id_spec_t spec = { 0 };
-  xcb_res_query_client_ids_cookie_t cookie;
-  xcb_res_query_client_ids_reply_t *reply = NULL;
-  uint32_t pid = 0, *value;
-
-  spec.client = client;
-  spec.mask = XCB_RES_CLIENT_ID_MASK_LOCAL_CLIENT_PID;
-
-  cookie = xcb_res_query_client_ids (xcb, 1, &spec);
-  reply = xcb_res_query_client_ids_reply (xcb, cookie, NULL);
-
-  if (reply == NULL)
-    return 0;
-
-  xcb_res_client_id_value_iterator_t it;
-  for (it = xcb_res_query_client_ids_ids_iterator (reply);
-       it.rem;
-       xcb_res_client_id_value_next (&it))
-    {
-      spec = it.data->spec;
-      if (spec.mask & XCB_RES_CLIENT_ID_MASK_LOCAL_CLIENT_PID)
-        {
-          value = xcb_res_client_id_value_value (it.data);
-          pid = *value;
-          break;
-        }
-    }
-  free (reply);
-
-  return pid;
-}
-
-static gboolean
-can_terminate_xwayland (Display *xdisplay)
-{
-  xcb_connection_t *xcb = XGetXCBConnection (xdisplay);
-  xcb_res_query_clients_cookie_t cookie;
-  xcb_res_query_clients_reply_t *reply = NULL;
-  xcb_res_client_iterator_t it;
-  gboolean can_terminate;
-  char *self;
-
-  cookie = xcb_res_query_clients (xcb);
-  reply = xcb_res_query_clients_reply (xcb, cookie, NULL);
-
-  /* Could not get the list of X11 clients, better not terminate Xwayland */
-  if (reply == NULL)
-    return FALSE;
-
-  can_terminate = TRUE;
-  self = meta_xwayland_get_self_exe ();
-  for (it = xcb_res_query_clients_clients_iterator (reply);
-       it.rem && can_terminate;
-       xcb_res_client_next (&it))
-    {
-      uint32_t pid;
-      char *executable;
-
-      pid = meta_xwayland_get_client_pid (xcb, it.data->resource_base);
-      if (pid == 0)
-        {
-          /* Unknown PID, don't risk terminating it */
-          can_terminate = FALSE;
-          break;
-        }
-
-      executable = meta_xwayland_get_exe_from_pid (pid);
-      can_terminate = can_xwayland_ignore_exe (executable, self);
-      g_free (executable);
-    }
-  free (reply);
-
-  return can_terminate;
-}
-
 static gboolean
 try_display (int      display,
              char   **filename_out,
@@ -595,19 +455,6 @@ static gboolean
 shutdown_xwayland_cb (gpointer data)
 {
   MetaXWaylandManager *manager = data;
-  MetaDisplay *display = meta_get_display ();
-  MetaBackend *backend = meta_get_backend ();
-
-  if (!meta_settings_is_experimental_feature_enabled (meta_backend_get_settings (backend),
-                                                      META_EXPERIMENTAL_FEATURE_AUTOCLOSE_XWAYLAND))
-    {
-      manager->xserver_grace_period_id = 0;
-      return G_SOURCE_REMOVE;
-    }
-
-  if (display->x11_display &&
-      !can_terminate_xwayland (display->x11_display->xdisplay))
-    return G_SOURCE_CONTINUE;
 
   meta_verbose ("Shutting down Xwayland");
   manager->xserver_grace_period_id = 0;
@@ -952,6 +799,12 @@ meta_xwayland_start_xserver (MetaXWaylandManager *manager,
   const char *args[32];
   int xwayland_disable_extensions;
   int i, j;
+#ifdef HAVE_XWAYLAND_TERMINATE_DELAY
+  MetaWaylandCompositor *compositor =
+    meta_wayland_compositor_get_default ();
+  MetaX11DisplayPolicy x11_display_policy =
+    meta_context_get_x11_display_policy (compositor->context);
+#endif
 
   task = g_task_new (NULL, cancellable, callback, user_data);
   g_task_set_source_tag (task, meta_xwayland_start_xserver);
@@ -1030,6 +883,16 @@ meta_xwayland_start_xserver (MetaXWaylandManager *manager,
 #else
   args[i++] = XWAYLAND_LISTENFD;
   args[i++] = "7";
+#endif
+#ifdef HAVE_XWAYLAND_TERMINATE_DELAY
+  if (x11_display_policy == META_X11_DISPLAY_POLICY_ON_DEMAND &&
+      meta_settings_is_experimental_feature_enabled (settings,
+                                                     META_EXPERIMENTAL_FEATURE_AUTOCLOSE_XWAYLAND))
+    {
+      /* Terminate after a 10 seconds delay */
+      args[i++] = "-terminate";
+      args[i++] = "10";
+    }
 #endif
   for (j = 0; j <  G_N_ELEMENTS (x11_extension_names); j++)
     {