From e2c1fa073202c4308bc8e66ec96d1b07678a3a75 Mon Sep 17 00:00:00 2001
From: luckysmg <2539699336@qq.com>
Date: Sat, 4 Feb 2023 08:49:03 +0800
Subject: [PATCH] [iOS] Ensure FlutterView's background color is not nil to
 avoid CAMetalLayer nextDrawable being time-consuming

---
 shell/platform/darwin/ios/framework/Source/FlutterView.mm   | 6 ++++++
 .../platform/darwin/ios/framework/Source/FlutterViewTest.mm | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/shell/platform/darwin/ios/framework/Source/FlutterView.mm b/shell/platform/darwin/ios/framework/Source/FlutterView.mm
index 7c188be87109d..dcab55d404c34 100644
--- a/shell/platform/darwin/ios/framework/Source/FlutterView.mm
+++ b/shell/platform/darwin/ios/framework/Source/FlutterView.mm
@@ -47,6 +47,12 @@ - (instancetype)initWithDelegate:(id<FlutterViewEngineDelegate>)delegate opaque:
   if (self) {
     _delegate = delegate;
     self.layer.opaque = opaque;
+
+    // This line is necessary. CoreAnimation(or UIKit) may take this to do
+    // something to compute the final frame presented on screen, if we don't set this,
+    // it will make it take long time for us to take next CAMetalDrawable and will
+    // cause constant junk during rendering.
+    self.backgroundColor = UIColor.clearColor;
   }
 
   return self;
diff --git a/shell/platform/darwin/ios/framework/Source/FlutterViewTest.mm b/shell/platform/darwin/ios/framework/Source/FlutterViewTest.mm
index c14bee16a6104..d264933b0bf43 100644
--- a/shell/platform/darwin/ios/framework/Source/FlutterViewTest.mm
+++ b/shell/platform/darwin/ios/framework/Source/FlutterViewTest.mm
@@ -49,4 +49,10 @@ - (void)testFlutterViewEnableSemanticsWhenIsAccessibilityElementIsCalled {
   XCTAssertTrue(delegate.callbackCalled);
 }
 
+- (void)testFlutterViewBackgroundColorIsNotNil {
+  FakeDelegate* delegate = [[FakeDelegate alloc] init];
+  FlutterView* view = [[FlutterView alloc] initWithDelegate:delegate opaque:NO];
+  XCTAssertNotNil(view.backgroundColor);
+}
+
 @end