Update zh_CN translation

The seat capability updating is synchronous, but input events are
asynchronous (first queued then emitted). This means we may end up in a
situation where we from libinput first may receive a key event,
immediately followed by a device-removed event. Clutter will first
queue the key event, then remove the device, immediately triggering the
seat capability removal.

Later, when the clutter stage processes the queued events, the
previously queued key event will be processed, eventually making it
into MetaWaylandSeat. Before this patch, MetaWaylandSeat would still
forward the key event to MetaWaylandKeyboard, even though it had
'released' it. Doing this would cause referencing potentially freed
memory, such as the xkb state that was unreferenced when the seat
removed the capability.

In order to avoid processing these lingering events, for now, just drop
them on the floor if the capability has been removed.

Eventually, the event queuing etc needs to be redesigned to work better
when used in a Wayland compositor, but for now at least don't access
freed memory.

https://bugzilla.gnome.org/show_bug.cgi?id=770727

src/wayland/meta-wayland-seat.c

@@ -300,18 +300,21 @@ meta_wayland_seat_update (MetaWaylandSeat    *seat,
     case CLUTTER_BUTTON_PRESS:
     case CLUTTER_BUTTON_RELEASE:
     case CLUTTER_SCROLL:
-      meta_wayland_pointer_update (&seat->pointer, event);
+      if (seat->capabilities & WL_SEAT_CAPABILITY_POINTER)
+        meta_wayland_pointer_update (&seat->pointer, event);
       break;
 
     case CLUTTER_KEY_PRESS:
     case CLUTTER_KEY_RELEASE:
-      meta_wayland_keyboard_update (&seat->keyboard, (const ClutterKeyEvent *) event);
+      if (seat->capabilities & WL_SEAT_CAPABILITY_KEYBOARD)
+        meta_wayland_keyboard_update (&seat->keyboard, (const ClutterKeyEvent *) event);
       break;
 
     case CLUTTER_TOUCH_BEGIN:
     case CLUTTER_TOUCH_UPDATE:
     case CLUTTER_TOUCH_END:
-      meta_wayland_touch_update (&seat->touch, event);
+      if (seat->capabilities & WL_SEAT_CAPABILITY_TOUCH)
+        meta_wayland_touch_update (&seat->touch, event);
       break;
 
     default:
@@ -334,16 +337,19 @@ meta_wayland_seat_handle_event (MetaWaylandSeat *seat,
     case CLUTTER_SCROLL:
     case CLUTTER_TOUCHPAD_SWIPE:
     case CLUTTER_TOUCHPAD_PINCH:
-      return meta_wayland_pointer_handle_event (&seat->pointer, event);
+      if (seat->capabilities & WL_SEAT_CAPABILITY_POINTER)
+        return meta_wayland_pointer_handle_event (&seat->pointer, event);
 
     case CLUTTER_KEY_PRESS:
     case CLUTTER_KEY_RELEASE:
-      return meta_wayland_keyboard_handle_event (&seat->keyboard,
-                                                 (const ClutterKeyEvent *) event);
+      if (seat->capabilities & WL_SEAT_CAPABILITY_KEYBOARD)
+        return meta_wayland_keyboard_handle_event (&seat->keyboard,
+                                                   (const ClutterKeyEvent *) event);
     case CLUTTER_TOUCH_BEGIN:
     case CLUTTER_TOUCH_UPDATE:
     case CLUTTER_TOUCH_END:
-      return meta_wayland_touch_handle_event (&seat->touch, event);
+      if (seat->capabilities & WL_SEAT_CAPABILITY_TOUCH)
+        return meta_wayland_touch_handle_event (&seat->touch, event);
 
     default:
       break;