input: Don't cache pointer grab interface between calls to focus and motion

The focus callback for the current grab can change the grab, so we have
to make sure we call the motion callback for the currently active grab.

https://bugs.freedesktop.org/show_bug.cgi?id=65961

src/input.c

@@ -46,13 +46,12 @@ static void unbind_resource(struct wl_resource *resource)
 void
 weston_seat_repick(struct weston_seat *seat)
 {
-	const struct weston_pointer_grab_interface *interface;
+	const struct weston_pointer *pointer = seat->pointer;
 
-	if (seat->pointer == NULL)
+	if (pointer == NULL)
 		return;
 
-	interface = seat->pointer->grab->interface;
-	interface->focus(seat->pointer->grab);
+	pointer->grab->interface->focus(seat->pointer->grab);
 }
 
 static void
@@ -531,22 +530,16 @@ WL_EXPORT void
 weston_pointer_start_grab(struct weston_pointer *pointer,
 			  struct weston_pointer_grab *grab)
 {
-	const struct weston_pointer_grab_interface *interface;
-
 	pointer->grab = grab;
-	interface = pointer->grab->interface;
 	grab->pointer = pointer;
-	interface->focus(pointer->grab);
+	pointer->grab->interface->focus(pointer->grab);
 }
 
 WL_EXPORT void
 weston_pointer_end_grab(struct weston_pointer *pointer)
 {
-	const struct weston_pointer_grab_interface *interface;
-
 	pointer->grab = &pointer->default_grab;
-	interface = pointer->grab->interface;
-	interface->focus(pointer->grab);
+	pointer->grab->interface->focus(pointer->grab);
 }
 
 WL_EXPORT void
@@ -637,7 +630,6 @@ WL_EXPORT void
 notify_motion(struct weston_seat *seat,
 	      uint32_t time, wl_fixed_t dx, wl_fixed_t dy)
 {
-	const struct weston_pointer_grab_interface *interface;
 	struct weston_compositor *ec = seat->compositor;
 	struct weston_pointer *pointer = seat->pointer;
 
@@ -645,16 +637,14 @@ notify_motion(struct weston_seat *seat,
 
 	move_pointer(seat, pointer->x + dx, pointer->y + dy);
 
-	interface = pointer->grab->interface;
-	interface->focus(pointer->grab);
-	interface->motion(pointer->grab, time);
+	pointer->grab->interface->focus(pointer->grab);
+	pointer->grab->interface->motion(pointer->grab, time);
 }
 
 WL_EXPORT void
 notify_motion_absolute(struct weston_seat *seat,
 		       uint32_t time, wl_fixed_t x, wl_fixed_t y)
 {
-	const struct weston_pointer_grab_interface *interface;
 	struct weston_compositor *ec = seat->compositor;
 	struct weston_pointer *pointer = seat->pointer;
 
@@ -662,9 +652,8 @@ notify_motion_absolute(struct weston_seat *seat,
 
 	move_pointer(seat, x, y);
 
-	interface = pointer->grab->interface;
-	interface->focus(pointer->grab);
-	interface->motion(pointer->grab, time);
+	pointer->grab->interface->focus(pointer->grab);
+	pointer->grab->interface->motion(pointer->grab, time);
 }
 
 WL_EXPORT void