From 1fa9cd33a2ac2830e358c1e403613c7f3503abaf Mon Sep 17 00:00:00 2001
From: Tommy Nguyen <tonguye@microsoft.com>
Date: Sun, 7 Jun 2020 22:07:53 +0200
Subject: [PATCH] Alleviate excessive layout jittering when resizing window

---
 React/Base/macOS/RCTUIKit.m | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/React/Base/macOS/RCTUIKit.m b/React/Base/macOS/RCTUIKit.m
index 395944a14df823..db0cc39f6f3b26 100644
--- a/React/Base/macOS/RCTUIKit.m
+++ b/React/Base/macOS/RCTUIKit.m
@@ -13,6 +13,8 @@
 
 #import <objc/runtime.h>
 
+#define RCT_LAYOUT_THROTTLE 0.25
+
 static char RCTGraphicsContextSizeKey;
 
 //
@@ -209,6 +211,9 @@ @implementation RCTUIView // TODO(macOS ISS#3536887)
   BOOL _clipsToBounds;
   BOOL _opaque;
   BOOL _userInteractionEnabled;
+
+  NSDate *_lastLayout;
+  BOOL _throttleLayout;
 }
 
 + (NSSet<NSString *> *)keyPathsForValuesAffectingValueForKey:(NSString *)key
@@ -236,7 +241,7 @@ @implementation RCTUIView // TODO(macOS ISS#3536887)
   if (self != nil) {
     self.wantsLayer = YES;
     self->_userInteractionEnabled = YES;
-
+    self->_lastLayout = [NSDate new];
   }
   return self;
 }
@@ -329,8 +334,22 @@ - (void)drawRect:(CGRect)rect
 
 - (void)layout
 {
-  if (self.window != nil) {
-    [self layoutSubviews];
+  if (self.window != nil && !_throttleLayout) {
+    NSTimeInterval interval = [[NSDate date] timeIntervalSinceDate:_lastLayout];
+    if (interval >= RCT_LAYOUT_THROTTLE) {
+      _lastLayout = [NSDate new];
+      [self layoutSubviews];
+    } else {
+      _throttleLayout = YES;
+      __weak typeof(self) weakSelf = self;
+      dispatch_after(dispatch_time(DISPATCH_TIME_NOW, RCT_LAYOUT_THROTTLE * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
+        typeof(self) strongSelf = weakSelf;
+        if (strongSelf != nil) {
+          strongSelf->_throttleLayout = NO;
+          [strongSelf setNeedsLayout];
+        }
+      });
+    }
   }
 }