From d61d7758ed36a517daedbeeea7e170509936734c Mon Sep 17 00:00:00 2001
From: Todd Volkert <tvolkert@users.noreply.github.com>
Date: Thu, 24 Dec 2020 21:42:25 -0800
Subject: [PATCH] Add comment to RenderColoredBox.paint() (#72526)

---
 packages/flutter/lib/src/widgets/basic.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/flutter/lib/src/widgets/basic.dart b/packages/flutter/lib/src/widgets/basic.dart
index e37e7a21265..343b911e389 100644
--- a/packages/flutter/lib/src/widgets/basic.dart
+++ b/packages/flutter/lib/src/widgets/basic.dart
@@ -7683,6 +7683,10 @@ class _RenderColoredBox extends RenderProxyBoxWithHitTestBehavior {
 
   @override
   void paint(PaintingContext context, Offset offset) {
+    // It's tempting to want to optimize out this `drawRect()` call if the
+    // color is transparent (alpha==0), but doing so would be incorrect. See
+    // https://github.com/flutter/flutter/pull/72526#issuecomment-749185938 for
+    // a good description of why.
     if (size > Size.zero) {
       context.canvas.drawRect(offset & size, Paint()..color = color);
     }