From 12f8b2598fa46533ea59834a0225cc9e36b20111 Mon Sep 17 00:00:00 2001
From: Boyang Yu <boyangyu@fb.com>
Date: Fri, 1 May 2020 12:37:58 -0700
Subject: [PATCH] fix duration calculation for RCTUIImageViewAnimated

Summary:
## Changelog:
[iOS] [Fixed] - Fix duration calculation for RCTUIImageViewAnimated

Reviewed By: p-sun, shergin

Differential Revision: D21321089

fbshipit-source-id: 7464231bbc3b90e70d3ba95288fd90707d3d24af
---
 Libraries/Image/RCTUIImageViewAnimated.m | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/Libraries/Image/RCTUIImageViewAnimated.m b/Libraries/Image/RCTUIImageViewAnimated.m
index 979b9aff3a4336..8402d0e28bb958 100644
--- a/Libraries/Image/RCTUIImageViewAnimated.m
+++ b/Libraries/Image/RCTUIImageViewAnimated.m
@@ -183,7 +183,21 @@ - (void)displayDidRefresh:(CADisplayLink *)displayLink
   // TODO: `displayLink.frameInterval` is not available on UIKitForMac
   NSTimeInterval duration = displayLink.duration;
 #else
-  NSTimeInterval duration = displayLink.duration * displayLink.preferredFramesPerSecond;
+  NSTimeInterval duration = displayLink.duration;
+  if (@available(iOS 10.0, *)) {
+    // Per https://developer.apple.com/documentation/quartzcore/cadisplaylink
+    // displayLink.duration provides the amount of time between frames at the maximumFramesPerSecond
+    // Thus we need to calculate true duration based on preferredFramesPerSecond
+    if (displayLink.preferredFramesPerSecond != 0) {
+      double maxFrameRate = 60.0; // default to 60 fps
+      if (@available(iOS 10.3, tvOS 10.3, *)) {
+        maxFrameRate = self.window.screen.maximumFramesPerSecond;
+      }
+      duration = duration * displayLink.preferredFramesPerSecond / maxFrameRate;
+    } // else respect maximumFramesPerSecond
+  } else { // version < (ios 10)
+    duration = duration * displayLink.frameInterval;
+  }
 #endif
   NSUInteger totalFrameCount = self.totalFrameCount;
   NSUInteger currentFrameIndex = self.currentFrameIndex;