From 8d7071ea463a1304ffbf5f795a8214efa2a2e72a Mon Sep 17 00:00:00 2001
From: Ferhat <ferhat@gmail.com>
Date: Tue, 21 Apr 2020 23:00:02 -0700
Subject: [PATCH] Prevent unnecessary DOM append call when canvas is reused
 (#17864)

---
 lib/web_ui/lib/src/engine/canvas_pool.dart | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/web_ui/lib/src/engine/canvas_pool.dart b/lib/web_ui/lib/src/engine/canvas_pool.dart
index 56d80200233..85a50d758e6 100644
--- a/lib/web_ui/lib/src/engine/canvas_pool.dart
+++ b/lib/web_ui/lib/src/engine/canvas_pool.dart
@@ -130,7 +130,12 @@ class _CanvasPool extends _SaveStackTracking {
     if (isFirstChildElement) {
       _canvas.style.zIndex = '-1';
     }
-    _rootElement.append(_canvas);
+    // Before appending canvas, check if canvas is already on rootElement. This
+    // optimization prevents DOM .append call when a PersistentSurface is
+    // reused. Reading lastChild is faster than append call.
+    if (_rootElement.lastChild != _canvas) {
+      _rootElement.append(_canvas);
+    }
     _context = _canvas.context2D;
     _contextHandle = ContextStateHandle(_context);
     _initializeViewport(requiresClearRect);