Merge pull request godotengine#8 from lawnjelly/duplicate_speedup

Cache packed scenes during duplication

scene/main/node.cpp

@@ -2215,14 +2215,40 @@ Node *Node::_duplicate(int p_flags, Map<const Node *, Node *> *r_duplimap) const
 
 	bool instanced = false;
 
+	// No need to load a packed scene more than once if features
+	// several times in the branch being duplicated.
+	struct LoadedPackedScene {
+		Ref<PackedScene> scene;
+		String filename;
+	};
+	LocalVector<LoadedPackedScene> loaded_scenes;
+
 	if (Object::cast_to<InstancePlaceholder>(this)) {
 		const InstancePlaceholder *ip = Object::cast_to<const InstancePlaceholder>(this);
 		InstancePlaceholder *nip = memnew(InstancePlaceholder);
 		nip->set_instance_path(ip->get_instance_path());
 		node = nip;
 
 	} else if ((p_flags & DUPLICATE_USE_INSTANCING) && get_filename() != String()) {
-		Ref<PackedScene> res = ResourceLoader::load(get_filename());
+		// already loaded?
+		int found = -1;
+		for (unsigned int n = 0; n < loaded_scenes.size(); n++) {
+			if (loaded_scenes[n].filename == get_filename()) {
+				found = n;
+				break;
+			}
+		}
+		Ref<PackedScene> res = Ref<PackedScene>();
+		if (found != -1) {
+			res = loaded_scenes[found].scene;
+		} else {
+			LoadedPackedScene ps;
+			ps.filename = get_filename();
+			ps.scene = ResourceLoader::load(get_filename());
+			res = ps.scene;
+			loaded_scenes.push_back(ps);
+		}
+
 		ERR_FAIL_COND_V(res.is_null(), nullptr);
 		PackedScene::GenEditState ges = PackedScene::GEN_EDIT_STATE_DISABLED;
 #ifdef TOOLS_ENABLED