scene: constify subsurface_tree_set_clip()

include/wlr/types/wlr_scene.h

@@ -556,7 +556,7 @@ struct wlr_scene_tree *wlr_scene_subsurface_tree_create(
  * A NULL or empty clip will disable clipping
  */
 void wlr_scene_subsurface_tree_set_clip(struct wlr_scene_node *node,
-	struct wlr_box *clip);
+	const struct wlr_box *clip);
 
 /**
  * Add a node displaying an xdg_surface and all of its sub-surfaces to the

types/scene/subsurface_tree.c

@@ -326,7 +326,7 @@ static struct wlr_scene_subsurface_tree *get_subsurface_tree_from_node(
 }
 
 static bool subsurface_tree_set_clip(struct wlr_scene_node *node,
-		struct wlr_box *clip) {
+		const struct wlr_box *clip) {
 	if (node->type != WLR_SCENE_NODE_TREE) {
 		return false;
 	}
@@ -360,7 +360,7 @@ static bool subsurface_tree_set_clip(struct wlr_scene_node *node,
 }
 
 void wlr_scene_subsurface_tree_set_clip(struct wlr_scene_node *node,
-		struct wlr_box *clip) {
+		const struct wlr_box *clip) {
 #ifndef NDEBUG
 	bool found =
 #endif