wayland: don't try to use seat devices that aren't (yet) present

Before commit ac448bd42b the pointer,
keyboard, and touch objects were initialized when the seat was created.
Now they're initialized later, when the clutter device manager finds and
loads them.

This commit makes sure we don't try to access those objects if they
aren't initialized.

https://bugzilla.gnome.org/show_bug.cgi?id=744640

src/wayland/meta-wayland-seat.c

@@ -44,6 +44,7 @@ seat_get_pointer (struct wl_client *client,
   MetaWaylandSeat *seat = wl_resource_get_user_data (resource);
   MetaWaylandPointer *pointer = &seat->pointer;
 
+  if ((seat->capabilities & WL_SEAT_CAPABILITY_POINTER) != 0)
     meta_wayland_pointer_create_new_resource (pointer, client, resource, id);
 }
 
@@ -55,6 +56,7 @@ seat_get_keyboard (struct wl_client *client,
   MetaWaylandSeat *seat = wl_resource_get_user_data (resource);
   MetaWaylandKeyboard *keyboard = &seat->keyboard;
 
+  if ((seat->capabilities & WL_SEAT_CAPABILITY_KEYBOARD) != 0)
     meta_wayland_keyboard_create_new_resource (keyboard, client, resource, id);
 }
 
@@ -66,6 +68,7 @@ seat_get_touch (struct wl_client *client,
   MetaWaylandSeat *seat = wl_resource_get_user_data (resource);
   MetaWaylandTouch *touch = &seat->touch;
 
+  if ((seat->capabilities & WL_SEAT_CAPABILITY_TOUCH) != 0)
     meta_wayland_touch_create_new_resource (touch, client, resource, id);
 }
 
@@ -350,6 +353,9 @@ meta_wayland_seat_handle_event (MetaWaylandSeat *seat,
 void
 meta_wayland_seat_repick (MetaWaylandSeat *seat)
 {
+  if ((seat->capabilities & WL_SEAT_CAPABILITY_POINTER) == 0)
+    return;
+
   meta_wayland_pointer_repick (&seat->pointer);
 }
 
@@ -357,6 +363,9 @@ void
 meta_wayland_seat_set_input_focus (MetaWaylandSeat    *seat,
                                    MetaWaylandSurface *surface)
 {
+  if ((seat->capabilities & WL_SEAT_CAPABILITY_KEYBOARD) == 0)
+    return;
+
   meta_wayland_keyboard_set_focus (&seat->keyboard, surface);
   meta_wayland_data_device_set_keyboard_focus (&seat->data_device);
 }
@@ -364,6 +373,9 @@ meta_wayland_seat_set_input_focus (MetaWaylandSeat    *seat,
 void
 meta_wayland_seat_update_cursor_surface (MetaWaylandSeat *seat)
 {
+  if ((seat->capabilities & WL_SEAT_CAPABILITY_POINTER) == 0)
+    return;
+
   meta_wayland_pointer_update_cursor_surface (&seat->pointer);
 }
 
@@ -374,21 +386,29 @@ meta_wayland_seat_get_grab_info (MetaWaylandSeat    *seat,
 				 gfloat             *x,
 				 gfloat             *y)
 {
-  ClutterEventSequence *sequence;
+  ClutterEventSequence *sequence = NULL;
+  gboolean can_grab_surface = FALSE;
 
+  if ((seat->capabilities & WL_SEAT_CAPABILITY_TOUCH) != 0)
     sequence = meta_wayland_touch_find_grab_sequence (&seat->touch, surface, serial);
 
   if (sequence)
+    {
       meta_wayland_touch_get_press_coords (&seat->touch, sequence, x, y);
-  else if (meta_wayland_pointer_can_grab_surface (&seat->pointer, surface, serial))
+    }
+  else
+    {
+      if ((seat->capabilities & WL_SEAT_CAPABILITY_POINTER) != 0)
+        can_grab_surface = meta_wayland_pointer_can_grab_surface (&seat->pointer, surface, serial);
+
+      if (can_grab_surface)
         {
           if (x)
             *x = seat->pointer.grab_x;
           if (y)
             *y = seat->pointer.grab_y;
         }
-  else
+    }
-    return FALSE;
 
-  return TRUE;
+  return sequence || can_grab_surface;
 }