Refine children cache invalidation to skip more special cases.

Author: WhalesState

scene/main/node.cpp

@@ -1643,22 +1643,29 @@ void Node::_add_child_nocheck(Node *p_child, const StringName &p_name, InternalM
 	data.children.insert(p_name, p_child);
 
 	p_child->data.internal_mode = p_internal_mode;
+
+	bool can_push_back = false;
 	switch (p_internal_mode) {
 		case INTERNAL_MODE_FRONT: {
 			p_child->data.index = data.internal_children_front_count_cache++;
+			// Safe to push back when ordinary and back children are empty.
+			can_push_back = (data.external_children_count_cache + data.internal_children_back_count_cache) == 0;
 		} break;
 		case INTERNAL_MODE_BACK: {
 			p_child->data.index = data.internal_children_back_count_cache++;
+			// Safe to push back when cache is valid.
+			can_push_back = true;
 		} break;
 		case INTERNAL_MODE_DISABLED: {
 			p_child->data.index = data.external_children_count_cache++;
+			// Safe to push back when back children are empty.
+			can_push_back = data.internal_children_back_count_cache == 0;
 		} break;
 	}
 
 	p_child->data.parent = this;
 
-	if (!data.children_cache_dirty && p_internal_mode == INTERNAL_MODE_DISABLED && data.internal_children_back_count_cache == 0) {
-		// Special case, also add to the cached children array since its cheap.
+	if (!data.children_cache_dirty && can_push_back) {
 		data.children_cache.push_back(p_child);
 	} else {
 		data.children_cache_dirty = true;

scene/main/node.h

@@ -167,7 +167,7 @@ class Node : public Object {
 		Node *parent = nullptr;
 		Node *owner = nullptr;
 		HashMap<StringName, Node *> children;
-		mutable bool children_cache_dirty = true;
+		mutable bool children_cache_dirty = false;
 		mutable LocalVector<Node *> children_cache;
 		HashMap<StringName, Node *> owned_unique_nodes;
 		bool unique_name_in_owner = false;