backend: Add API to get layout group

Add API to get the layout group (layout index) currently active. In the
native backend this is done by fetching the state directly from the
evdev backend; on X11 this works by listening for XkbStateNotify
events, caching the layout group value.

https://bugzilla.gnome.org/show_bug.cgi?id=786408

src/backends/meta-backend-private.h

@@ -83,6 +83,8 @@ struct _MetaBackendClass
 
   struct xkb_keymap * (* get_keymap) (MetaBackend *backend);
 
+  xkb_layout_index_t (* get_keymap_layout_group) (MetaBackend *backend);
+
   void (* lock_layout_group) (MetaBackend *backend,
                               guint        idx);
 
@@ -133,6 +135,8 @@ MetaLogicalMonitor * meta_backend_get_current_logical_monitor (MetaBackend *back
 
 struct xkb_keymap * meta_backend_get_keymap (MetaBackend *backend);
 
+xkb_layout_index_t meta_backend_get_keymap_layout_group (MetaBackend *backend);
+
 void meta_backend_update_last_device (MetaBackend *backend,
                                       int          device_id);
 

src/backends/meta-backend.c

@@ -699,6 +699,12 @@ meta_backend_get_keymap (MetaBackend *backend)
   return META_BACKEND_GET_CLASS (backend)->get_keymap (backend);
 }
 
+xkb_layout_index_t
+meta_backend_get_keymap_layout_group (MetaBackend *backend)
+{
+  return META_BACKEND_GET_CLASS (backend)->get_keymap_layout_group (backend);
+}
+
 void
 meta_backend_lock_layout_group (MetaBackend *backend,
                                 guint idx)

src/backends/native/meta-backend-native.c

@@ -507,6 +507,14 @@ meta_backend_native_get_keymap (MetaBackend *backend)
   return clutter_evdev_get_keyboard_map (manager);
 }
 
+static xkb_layout_index_t
+meta_backend_native_get_keymap_layout_group (MetaBackend *backend)
+{
+  ClutterDeviceManager *manager = clutter_device_manager_get_default ();
+
+  return clutter_evdev_get_keyboard_layout_index (manager);
+}
+
 static void
 meta_backend_native_lock_layout_group (MetaBackend *backend,
                                        guint        idx)
@@ -579,6 +587,7 @@ meta_backend_native_class_init (MetaBackendNativeClass *klass)
 
   backend_class->set_keymap = meta_backend_native_set_keymap;
   backend_class->get_keymap = meta_backend_native_get_keymap;
+  backend_class->get_keymap_layout_group = meta_backend_native_get_keymap_layout_group;
   backend_class->lock_layout_group = meta_backend_native_lock_layout_group;
   backend_class->get_relative_motion_deltas = meta_backend_native_get_relative_motion_deltas;
   backend_class->update_screen_size = meta_backend_native_update_screen_size;

src/backends/x11/meta-backend-x11.c

@@ -67,6 +67,7 @@ struct _MetaBackendX11Private
   uint8_t xkb_error_base;
 
   struct xkb_keymap *keymap;
+  xkb_layout_index_t keymap_layout_group;
 
   MetaLogicalMonitor *cached_current_logical_monitor;
 };
@@ -282,12 +283,18 @@ handle_host_xevent (MetaBackend *backend,
 
       if (xkb_ev->any.device == META_VIRTUAL_CORE_KEYBOARD_ID)
         {
+          int layout_group;
+
           switch (xkb_ev->any.xkb_type)
             {
             case XkbNewKeyboardNotify:
             case XkbMapNotify:
               keymap_changed (backend);
               break;
+            case XkbStateNotify:
+              layout_group = xkb_ev->state.locked_group;
+              priv->keymap_layout_group = layout_group;
+              break;
             default:
               break;
             }
@@ -424,7 +431,6 @@ meta_backend_x11_post_init (MetaBackend *backend)
   if (!has_xi)
     meta_fatal ("X server doesn't have the XInput extension, version 2.2 or newer\n");
 
-  priv->xcb = XGetXCBConnection (priv->xdisplay);
   if (!xkb_x11_setup_xkb_extension (priv->xcb,
                                     XKB_X11_MIN_MAJOR_XKB_VERSION,
                                     XKB_X11_MIN_MINOR_XKB_VERSION,
@@ -568,6 +574,15 @@ meta_backend_x11_get_keymap (MetaBackend *backend)
   return priv->keymap;
 }
 
+static xkb_layout_index_t
+meta_backend_x11_get_keymap_layout_group (MetaBackend *backend)
+{
+  MetaBackendX11 *x11 = META_BACKEND_X11 (backend);
+  MetaBackendX11Private *priv = meta_backend_x11_get_instance_private (x11);
+
+  return priv->keymap_layout_group;
+}
+
 static void
 meta_backend_x11_set_numlock (MetaBackend *backend,
                               gboolean     numlock_state)
@@ -592,6 +607,25 @@ meta_backend_x11_get_xkb_event_base (MetaBackendX11 *x11)
   return priv->xkb_event_base;
 }
 
+static void
+init_xkb_state (MetaBackendX11 *x11)
+{
+  MetaBackendX11Private *priv = meta_backend_x11_get_instance_private (x11);
+  struct xkb_keymap *keymap;
+  int32_t device_id;
+  struct xkb_state *state;
+
+  keymap = meta_backend_get_keymap (META_BACKEND (x11));
+
+  device_id = xkb_x11_get_core_keyboard_device_id (priv->xcb);
+  state = xkb_x11_state_new_from_device (keymap, priv->xcb, device_id);
+
+  priv->keymap_layout_group =
+    xkb_state_serialize_layout (state, XKB_STATE_LAYOUT_LOCKED);
+
+  xkb_state_unref (state);
+}
+
 static gboolean
 meta_backend_x11_initable_init (GInitable    *initable,
                                 GCancellable *cancellable,
@@ -619,8 +653,11 @@ meta_backend_x11_initable_init (GInitable    *initable,
     }
 
   priv->xdisplay = xdisplay;
+  priv->xcb = XGetXCBConnection (priv->xdisplay);
   clutter_x11_set_display (xdisplay);
 
+  init_xkb_state (x11);
+
   return initable_parent_iface->init (initable, cancellable, error);
 }
 
@@ -645,6 +682,7 @@ meta_backend_x11_class_init (MetaBackendX11Class *klass)
   backend_class->warp_pointer = meta_backend_x11_warp_pointer;
   backend_class->get_current_logical_monitor = meta_backend_x11_get_current_logical_monitor;
   backend_class->get_keymap = meta_backend_x11_get_keymap;
+  backend_class->get_keymap_layout_group = meta_backend_x11_get_keymap_layout_group;
   backend_class->set_numlock = meta_backend_x11_set_numlock;
 }