[ReactNative] Use a single DisplayLink held by the bridge

React/Base/RCTBridge.h

@@ -10,6 +10,7 @@
 #import <UIKit/UIKit.h>
 
 #import "RCTBridgeModule.h"
+#import "RCTFrameUpdate.h"
 #import "RCTInvalidating.h"
 #import "RCTJavaScriptExecutor.h"
 
@@ -122,4 +123,14 @@ static const char *__rct_import_##module##_##method##__ = #module"."#method;
  */
 - (void)reload;
 
+/**
+ * Add a new observer that will be called on every screen refresh
+ */
+- (void)addFrameUpdateObserver:(id<RCTFrameUpdateObserver>)observer;
+
+/**
+ * Stop receiving screen refresh updates for the given observer
+ */
+- (void)removeFrameUpdateObserver:(id<RCTFrameUpdateObserver>)observer;
+
 @end

React/Base/RCTBridge.m

@@ -677,6 +677,73 @@ static NSDictionary *RCTLocalModulesConfig()
   return localModules;
 }
 
+@interface RCTDisplayLink : NSObject <RCTInvalidating>
+
+- (instancetype)initWithBridge:(RCTBridge *)bridge NS_DESIGNATED_INITIALIZER;
+
+@end
+
+@interface RCTBridge (RCTDisplayLink)
+
+- (void)_update:(CADisplayLink *)displayLink;
+
+@end
+
+@implementation RCTDisplayLink
+{
+  __weak RCTBridge *_bridge;
+  CADisplayLink *_displayLink;
+}
+
+- (instancetype)initWithBridge:(RCTBridge *)bridge
+{
+  if ((self = [super init])) {
+    _bridge = bridge;
+    _displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(_update:)];
+    [_displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
+  }
+  return self;
+}
+
+- (BOOL)isValid
+{
+  return _displayLink != nil;
+}
+
+- (void)invalidate
+{
+  if (self.isValid) {
+    [_displayLink invalidate];
+    _displayLink = nil;
+  }
+}
+
+- (void)_update:(CADisplayLink *)displayLink
+{
+  [_bridge _update:displayLink];
+}
+
+@end
+
+@interface RCTFrameUpdate (Private)
+
+- (instancetype)initWithDisplayLink:(CADisplayLink *)displayLink;
+
+@end
+
+@implementation RCTFrameUpdate
+
+- (instancetype)initWithDisplayLink:(CADisplayLink *)displayLink
+{
+  if ((self = [super init])) {
+    _timestamp = displayLink.timestamp;
+    _deltaTime = displayLink.duration;
+  }
+  return self;
+}
+
+@end
+
 @implementation RCTBridge
 {
   RCTSparseArray *_modulesByID;
@@ -685,6 +752,8 @@ static NSDictionary *RCTLocalModulesConfig()
   Class _executorClass;
   NSURL *_bundleURL;
   RCTBridgeModuleProviderBlock _moduleProvider;
+  RCTDisplayLink *_displayLink;
+  NSMutableSet *_frameUpdateObservers;
   BOOL _loading;
 }
 
@@ -711,6 +780,8 @@ static id<RCTJavaScriptExecutor> _latestJSExecutor;
   _latestJSExecutor = _javaScriptExecutor;
   _eventDispatcher = [[RCTEventDispatcher alloc] initWithBridge:self];
   _shadowQueue = dispatch_queue_create("com.facebook.React.ShadowQueue", DISPATCH_QUEUE_SERIAL);
+  _displayLink = [[RCTDisplayLink alloc] initWithBridge:self];
+  _frameUpdateObservers = [[NSMutableSet alloc] init];
 
   // Register passed-in module instances
   NSMutableDictionary *preregisteredModules = [[NSMutableDictionary alloc] init];
@@ -891,6 +962,9 @@ static id<RCTJavaScriptExecutor> _latestJSExecutor;
   [_javaScriptExecutor invalidate];
   _javaScriptExecutor = nil;
 
+  [_displayLink invalidate];
+  _frameUpdateObservers = nil;
+
   // Invalidate modules
   for (id target in _modulesByID.allObjects) {
     if ([target respondsToSelector:@selector(invalidate)]) {
@@ -1075,6 +1149,26 @@ static id<RCTJavaScriptExecutor> _latestJSExecutor;
   return YES;
 }
 
+- (void)_update:(CADisplayLink *)displayLink
+{
+  RCTFrameUpdate *frameUpdate = [[RCTFrameUpdate alloc] initWithDisplayLink:displayLink];
+  for (id<RCTFrameUpdateObserver> observer in _frameUpdateObservers) {
+    if (![observer respondsToSelector:@selector(isPaused)] || ![observer isPaused]) {
+      [observer didUpdateFrame:frameUpdate];
+    }
+  }
+}
+
+- (void)addFrameUpdateObserver:(id<RCTFrameUpdateObserver>)observer
+{
+  [_frameUpdateObservers addObject:observer];
+}
+
+- (void)removeFrameUpdateObserver:(id<RCTFrameUpdateObserver>)observer
+{
+  [_frameUpdateObservers removeObject:observer];
+}
+
 - (void)reload
 {
   if (!_loading) {

React/Base/RCTFrameUpdate.h

@@ -0,0 +1,44 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+/**
+ * Interface containing the information about the last screen refresh.
+ */
+@interface RCTFrameUpdate : NSObject
+
+/**
+ * Timestamp for the actual screen refresh
+ */
+@property (nonatomic, readonly) NSTimeInterval timestamp;
+
+/**
+ * Time since the last frame update ( >= 16.6ms )
+ */
+@property (nonatomic, readonly) NSTimeInterval deltaTime;
+
+@end
+
+/**
+ * Protocol that must be implemented for subscribing to display refreshes (DisplayLink updates)
+ */
+@protocol RCTFrameUpdateObserver <NSObject>
+
+/**
+ * Method called on every screen refresh (if paused != YES)
+ */
+- (void)didUpdateFrame:(RCTFrameUpdate *)update;
+
+@optional
+
+/**
+ * Synthesize and set to true to pause the calls to -[didUpdateFrame:]
+ */
+@property (nonatomic, assign, getter=isPaused) BOOL paused;
+
+@end

React/Modules/RCTTiming.h

@@ -10,8 +10,9 @@
 #import <Foundation/Foundation.h>
 
 #import "RCTBridgeModule.h"
+#import "RCTFrameUpdate.h"
 #import "RCTInvalidating.h"
 
-@interface RCTTiming : NSObject <RCTBridgeModule, RCTInvalidating>
+@interface RCTTiming : NSObject <RCTBridgeModule, RCTInvalidating, RCTFrameUpdateObserver>
 
 @end

React/Modules/RCTTiming.m

@@ -58,7 +58,6 @@
 @implementation RCTTiming
 {
   RCTSparseArray *_timers;
-  id _updateTimer;
 }
 
 @synthesize bridge = _bridge;
@@ -113,32 +112,21 @@ RCT_IMPORT_METHOD(RCTJSTimers, callTimers)
 
 - (void)stopTimers
 {
-  [_updateTimer invalidate];
+  [_bridge removeFrameUpdateObserver:self];
-  _updateTimer = nil;
 }
 
 - (void)startTimers
 {
   RCTAssertMainThread();
 
-  if (![self isValid] || _updateTimer != nil || _timers.count == 0) {
+  if (![self isValid] || _timers.count == 0) {
     return;
   }
 
-  _updateTimer = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];
+  [_bridge addFrameUpdateObserver:self];
-  if (_updateTimer) {
-    [_updateTimer addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
-  } else {
-    RCTLogWarn(@"Failed to create a display link (probably on buildbot) - using an NSTimer for AppEngine instead.");
-    _updateTimer = [NSTimer scheduledTimerWithTimeInterval:(1.0 / 60)
-                                                    target:self
-                                                  selector:@selector(update)
-                                                  userInfo:nil
-                                                   repeats:YES];
-  }
 }
 
-- (void)update
+- (void)didUpdateFrame:(RCTFrameUpdate *)update
 {
   RCTAssertMainThread();
 

React/React.xcodeproj/project.pbxproj

@@ -154,6 +154,7 @@
 		13E067541A70F44B002CDEE1 /* UIView+React.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "UIView+React.m"; sourceTree = "<group>"; };
 		14200DA81AC179B3008EE6BA /* RCTJavaScriptLoader.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RCTJavaScriptLoader.h; sourceTree = "<group>"; };
 		14200DA91AC179B3008EE6BA /* RCTJavaScriptLoader.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RCTJavaScriptLoader.m; sourceTree = "<group>"; };
+		1436DD071ADE7AA000A5ED7D /* RCTFrameUpdate.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = RCTFrameUpdate.h; sourceTree = "<group>"; };
 		14435CE11AAC4AE100FC20F4 /* RCTMap.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RCTMap.h; sourceTree = "<group>"; };
 		14435CE21AAC4AE100FC20F4 /* RCTMap.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RCTMap.m; sourceTree = "<group>"; };
 		14435CE31AAC4AE100FC20F4 /* RCTMapManager.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RCTMapManager.h; sourceTree = "<group>"; };
@@ -391,6 +392,7 @@
 				83CBBA971A6020BB00E9B192 /* RCTTouchHandler.m */,
 				83CBBA4F1A601E3B00E9B192 /* RCTUtils.h */,
 				83CBBA501A601E3B00E9B192 /* RCTUtils.m */,
+				1436DD071ADE7AA000A5ED7D /* RCTFrameUpdate.h */,
 			);
 			path = Base;
 			sourceTree = "<group>";

React/Views/RCTNavigator.h

@@ -9,16 +9,17 @@
 
 #import <UIKit/UIKit.h>
 
+#import "RCTFrameUpdate.h"
 #import "RCTInvalidating.h"
 
-@class RCTEventDispatcher;
+@class RCTBridge;
 
-@interface RCTNavigator : UIView <RCTInvalidating>
+@interface RCTNavigator : UIView <RCTFrameUpdateObserver>
 
 @property (nonatomic, strong) UIView *reactNavSuperviewLink;
 @property (nonatomic, assign) NSInteger requestedTopOfStack;
 
-- (instancetype)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithBridge:(RCTBridge *)bridge NS_DESIGNATED_INITIALIZER;
 
 /**
  * Schedules a JavaScript navigation and prevents `UIKit` from navigating until

React/Views/RCTNavigator.m

@@ -10,6 +10,7 @@
 #import "RCTNavigator.h"
 
 #import "RCTAssert.h"
+#import "RCTBridge.h"
 #import "RCTConvert.h"
 #import "RCTEventDispatcher.h"
 #import "RCTLog.h"
@@ -190,10 +191,6 @@ NSInteger kNeverProgressed = -10000;
 @end
 
 @interface RCTNavigator() <RCTWrapperViewControllerNavigationListener, UINavigationControllerDelegate>
-{
-  RCTEventDispatcher *_eventDispatcher;
-  NSInteger _numberOfViewControllerMovesToIgnore;
-}
 
 @property (nonatomic, assign) NSInteger previousRequestedTopOfStack;
 
@@ -251,7 +248,6 @@ NSInteger kNeverProgressed = -10000;
  *
  */
 @property (nonatomic, readonly, assign) CGFloat mostRecentProgress;
-@property (nonatomic, readwrite, strong) CADisplayLink *displayLink;
 @property (nonatomic, readonly, strong) NSTimer *runTimer;
 @property (nonatomic, readonly, assign) NSInteger currentlyTransitioningFrom;
 @property (nonatomic, readonly, assign) NSInteger currentlyTransitioningTo;
@@ -263,22 +259,17 @@ NSInteger kNeverProgressed = -10000;
 @end
 
 @implementation RCTNavigator
+{
+  __weak RCTBridge *_bridge;
+  NSInteger _numberOfViewControllerMovesToIgnore;
+}
 
-- (id)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher
+- (id)initWithBridge:(RCTBridge *)bridge
 {
   if ((self = [super initWithFrame:CGRectZero])) {
-    _displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(reportNavigationProgress:)];
+    _bridge = bridge;
     _mostRecentProgress = kNeverProgressed;
     _dummyView = [[UIView alloc] initWithFrame:CGRectZero];
-    if (_displayLink) {
-      [_displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
-      _displayLink.paused = YES;
-    } else {
-      // It's okay to leak this on a build bot.
-      RCTLogWarn(@"Failed to create a display link (probably on automated build system) - using an NSTimer for AppEngine instead.");
-     _runTimer = [NSTimer scheduledTimerWithTimeInterval:(1.0 / 60.0) target:self selector:@selector(reportNavigationProgress:) userInfo:nil repeats:YES];
-    }
-    _eventDispatcher = eventDispatcher;
     _previousRequestedTopOfStack = kNeverRequested; // So that we initialize with a push.
     _previousViews = @[];
     _currentViews = [[NSMutableArray alloc] initWithCapacity:0];
@@ -295,7 +286,7 @@ NSInteger kNeverProgressed = -10000;
   return self;
 }
 
-- (void)reportNavigationProgress:(CADisplayLink *)sender
+- (void)didUpdateFrame:(RCTFrameUpdate *)update
 {
   if (_currentlyTransitioningFrom != _currentlyTransitioningTo) {
     UIView *topView = _dummyView;
@@ -307,7 +298,7 @@ NSInteger kNeverProgressed = -10000;
       return;
     }
     _mostRecentProgress = nextProgress;
-    [_eventDispatcher sendInputEventWithName:@"topNavigationProgress" body:@{
+    [_bridge.eventDispatcher sendInputEventWithName:@"topNavigationProgress" body:@{
       @"fromIndex": @(_currentlyTransitioningFrom),
       @"toIndex": @(_currentlyTransitioningTo),
       @"progress": @(nextProgress),
@@ -350,16 +341,14 @@ NSInteger kNeverProgressed = -10000;
     _dummyView.frame = (CGRect){{destination}};
     _currentlyTransitioningFrom = indexOfFrom;
     _currentlyTransitioningTo = indexOfTo;
-    if (indexOfFrom != indexOfTo) {
+    [_bridge addFrameUpdateObserver:self];
-      _displayLink.paused = NO;
-    }
   }
   completion:^(id<UIViewControllerTransitionCoordinatorContext> context) {
     [weakSelf freeLock];
     _currentlyTransitioningFrom = 0;
     _currentlyTransitioningTo = 0;
     _dummyView.frame = CGRectZero;
-    _displayLink.paused = YES;
+    [_bridge removeFrameUpdateObserver:self];
     // Reset the parallel position tracker
   }];
 }
@@ -400,19 +389,6 @@ NSInteger kNeverProgressed = -10000;
   return _currentViews;
 }
 
-- (BOOL)isValid
-{
-  return _displayLink != nil;
-}
-
-- (void)invalidate
-{
-  // Prevent displayLink from retaining the navigator indefinitely
-  [_displayLink invalidate];
-  _displayLink = nil;
-  _runTimer = nil;
-}
-
 - (void)layoutSubviews
 {
   [super layoutSubviews];
@@ -430,7 +406,7 @@ NSInteger kNeverProgressed = -10000;
 
 - (void)handleTopOfStackChanged
 {
-  [_eventDispatcher sendInputEventWithName:@"topNavigateBack" body:@{
+  [_bridge.eventDispatcher sendInputEventWithName:@"topNavigateBack" body:@{
     @"target":self.reactTag,
     @"stackLength":@(_navigationController.viewControllers.count)
   }];
@@ -438,7 +414,7 @@ NSInteger kNeverProgressed = -10000;
 
 - (void)dispatchFakeScrollEvent
 {
-  [_eventDispatcher sendScrollEventWithType:RCTScrollEventTypeMove
+  [_bridge.eventDispatcher sendScrollEventWithType:RCTScrollEventTypeMove
                                    reactTag:self.reactTag
                                  scrollView:nil
                                    userData:nil];
@@ -511,7 +487,7 @@ NSInteger kNeverProgressed = -10000;
   if (jsGettingAhead) {
     if (reactPushOne) {
       UIView *lastView = [_currentViews lastObject];
-      RCTWrapperViewController *vc = [[RCTWrapperViewController alloc] initWithNavItem:(RCTNavItem *)lastView eventDispatcher:_eventDispatcher];
+      RCTWrapperViewController *vc = [[RCTWrapperViewController alloc] initWithNavItem:(RCTNavItem *)lastView eventDispatcher:_bridge.eventDispatcher];
       vc.navigationListener = self;
       _numberOfViewControllerMovesToIgnore = 1;
       [_navigationController pushViewController:vc animated:(currentReactCount > 1)];

React/Views/RCTNavigatorManager.m

@@ -21,7 +21,7 @@ RCT_EXPORT_MODULE()
 
 - (UIView *)view
 {
-  return [[RCTNavigator alloc] initWithEventDispatcher:self.bridge.eventDispatcher];
+  return [[RCTNavigator alloc] initWithBridge:self.bridge];
 }
 
 RCT_EXPORT_VIEW_PROPERTY(requestedTopOfStack, NSInteger)