From 040f241f392017e1a9767d728b9cd87f0f3f0860 Mon Sep 17 00:00:00 2001
From: aaronp64 <aaronp.code@gmail.com>
Date: Thu, 25 Jul 2024 13:57:32 -0400
Subject: Improve Tree performance

Added TreeItem::last_child to avoid needing to iterate through all children to get to the end.  This mainly helps in cases where one TreeItem has many children (1000s), and new children are added to the end, as each add had to iterate through all previously added children.
---
 scene/gui/tree.cpp | 63 +++++++++++++++++++++++++-----------------------------
 1 file changed, 29 insertions(+), 34 deletions(-)

(limited to 'scene/gui/tree.cpp')

diff --git a/scene/gui/tree.cpp b/scene/gui/tree.cpp
index 46fcdcf7f6..5830bea258 100644
--- a/scene/gui/tree.cpp
+++ b/scene/gui/tree.cpp
@@ -773,17 +773,21 @@ TreeItem *TreeItem::create_child(int p_index) {
 	TreeItem *item_prev = nullptr;
 	TreeItem *item_next = first_child;
 
-	int idx = 0;
-	while (item_next) {
-		if (idx == p_index) {
-			item_next->prev = ti;
-			ti->next = item_next;
-			break;
-		}
+	if (p_index < 0 && last_child) {
+		item_prev = last_child;
+	} else {
+		int idx = 0;
+		while (item_next) {
+			if (idx == p_index) {
+				item_next->prev = ti;
+				ti->next = item_next;
+				break;
+			}
 
-		item_prev = item_next;
-		item_next = item_next->next;
-		idx++;
+			item_prev = item_next;
+			item_next = item_next->next;
+			idx++;
+		}
 	}
 
 	if (item_prev) {
@@ -804,6 +808,10 @@ TreeItem *TreeItem::create_child(int p_index) {
 		}
 	}
 
+	if (item_prev == last_child) {
+		last_child = ti;
+	}
+
 	ti->parent = this;
 	ti->parent_visible_in_tree = is_visible_in_tree();
 
@@ -820,17 +828,13 @@ void TreeItem::add_child(TreeItem *p_item) {
 	p_item->parent_visible_in_tree = is_visible_in_tree();
 	p_item->_handle_visibility_changed(p_item->parent_visible_in_tree);
 
-	TreeItem *item_prev = first_child;
-	while (item_prev && item_prev->next) {
-		item_prev = item_prev->next;
-	}
-
-	if (item_prev) {
-		item_prev->next = p_item;
-		p_item->prev = item_prev;
+	if (last_child) {
+		last_child->next = p_item;
+		p_item->prev = last_child;
 	} else {
 		first_child = p_item;
 	}
+	last_child = p_item;
 
 	if (!children_cache.is_empty()) {
 		children_cache.append(p_item);
@@ -910,13 +914,8 @@ TreeItem *TreeItem::_get_prev_in_tree(bool p_wrap, bool p_include_invisible) {
 		}
 	} else {
 		current = prev_item;
-		while ((!current->collapsed || p_include_invisible) && current->first_child) {
-			//go to the very end
-
-			current = current->first_child;
-			while (current->next) {
-				current = current->next;
-			}
+		while ((!current->collapsed || p_include_invisible) && current->last_child) {
+			current = current->last_child;
 		}
 	}
 
@@ -1037,6 +1036,8 @@ void TreeItem::clear_children() {
 	}
 
 	first_child = nullptr;
+	last_child = nullptr;
+	children_cache.clear();
 };
 
 int TreeItem::get_index() {
@@ -1141,6 +1142,7 @@ void TreeItem::move_after(TreeItem *p_item) {
 	if (next) {
 		parent->children_cache.clear();
 	} else {
+		parent->last_child = this;
 		// If the cache is empty, it has not been built but there
 		// are items in the tree (note p_item != nullptr,) so we cannot update it.
 		if (!parent->children_cache.is_empty()) {
@@ -4468,15 +4470,8 @@ TreeItem *Tree::get_root() const {
 
 TreeItem *Tree::get_last_item() const {
 	TreeItem *last = root;
-
-	while (last) {
-		if (last->next) {
-			last = last->next;
-		} else if (last->first_child && !last->collapsed) {
-			last = last->first_child;
-		} else {
-			break;
-		}
+	while (last && last->last_child && !last->collapsed) {
+		last = last->last_child;
 	}
 
 	return last;
-- 
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