desktop-shell: Fix opaque region co-ordinate confusion

Opaque regions are in surface co-ordinate space, not global co-ordinate
space, so the region should be anchored to (0,0).

Signed-off-by: Daniel Stone <daniels@collabora.com>

desktop-shell/shell.c

@@ -586,7 +586,7 @@ create_focus_surface(struct weston_compositor *ec,
 	weston_view_set_position(fsurf->view, output->x, output->y);
 	weston_surface_set_color(surface, 0.0, 0.0, 0.0, 1.0);
 	pixman_region32_fini(&surface->opaque);
-	pixman_region32_init_rect(&surface->opaque, output->x, output->y,
+	pixman_region32_init_rect(&surface->opaque, 0, 0,
 				  output->width, output->height);
 	pixman_region32_fini(&surface->input);
 	pixman_region32_init(&surface->input);