Move VSyncWaiter to engien to simplify locking

Author: knopp

shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -22,6 +22,7 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewController.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterVSyncWaiter.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewEngineProvider.h"
 
@@ -459,6 +460,10 @@ @implementation FlutterEngine {
 
   // Proxy to allow plugins, channels to hold a weak reference to the binary messenger (self).
   FlutterBinaryMessengerRelay* _binaryMessenger;
+
+  // Map from ViewId to vsync waiter. Note that this is modified on main thread
+  // but accessed on UI thread, so access must be @synchronized.
+  NSMapTable<NSNumber*, FlutterVSyncWaiter*>* _vsyncWaiters;
 }
 
 - (instancetype)initWithName:(NSString*)labelPrefix project:(FlutterDartProject*)project {
@@ -528,6 +533,8 @@ - (instancetype)initWithName:(NSString*)labelPrefix
     _terminationHandler = nil;
   }
 
+  _vsyncWaiters = [NSMapTable strongToStrongObjectsMapTable];
+
   return self;
 }
 
@@ -721,6 +728,22 @@ - (void)registerViewController:(FlutterViewController*)controller forId:(Flutter
   [controller setUpWithEngine:self viewId:viewId threadSynchronizer:_threadSynchronizer];
   NSAssert(controller.viewId == viewId, @"Failed to assign view ID.");
   [_viewControllers setObject:controller forKey:@(viewId)];
+
+  __weak FlutterEngine* weakSelf = self;
+  FlutterVSyncWaiter* waiter = [[FlutterVSyncWaiter alloc]
+      initWithView:controller.view
+             block:^(CFTimeInterval timestamp, CFTimeInterval targetTimestamp, uintptr_t baton) {
+               // CAMediaTime and flutter time are both mach_absolute_time.
+               uint64_t timeNanos = timestamp * 1000000000;
+               uint64_t targetTimeNanos = targetTimestamp * 1000000000;
+               FlutterEngine* engine = weakSelf;
+               if (engine) {
+                 engine->_embedderAPI.OnVsync(_engine, baton, timeNanos, targetTimeNanos);
+               }
+             }];
+  @synchronized(_vsyncWaiters) {
+    [_vsyncWaiters setObject:waiter forKey:@(viewId)];
+  }
 }
 
 - (void)deregisterViewControllerForId:(FlutterViewId)viewId {
@@ -729,6 +752,9 @@ - (void)deregisterViewControllerForId:(FlutterViewId)viewId {
     [oldController detachFromEngine];
     [_viewControllers removeObjectForKey:@(viewId)];
   }
+  @synchronized(_vsyncWaiters) {
+    [_vsyncWaiters removeObjectForKey:@(viewId)];
+  }
 }
 
 - (void)shutDownIfNeeded {
@@ -1048,21 +1074,14 @@ - (void)engineCallbackOnPreEngineRestart {
 }
 
 - (void)onVSync:(uintptr_t)baton {
-  FlutterViewController* controller = [self viewControllerForId:kFlutterImplicitViewId];
-  if (controller) {
-    [controller waitForVSync:baton];
+  @synchronized(_vsyncWaiters) {
+    FlutterVSyncWaiter* waiter = [_vsyncWaiters objectForKey:@(kFlutterImplicitViewId)];
+    if (waiter) {
+      [waiter waitForVSync:baton];
+    }
   }
 }
 
-- (void)onVSyncWithTimestamp:(CFTimeInterval)timestamp
-             targetTimestamp:(CFTimeInterval)targetTimestamp
-                       baton:(uintptr_t)baton {
-  // CAMediaTime and flutter time are both mach_absolute_time.
-  uint64_t timeNanos = timestamp * 1000000000;
-  uint64_t targetTimeNanos = targetTimestamp * 1000000000;
-  _embedderAPI.OnVsync(_engine, baton, timeNanos, targetTimeNanos);
-}
-
 /**
  * Note: Called from dealloc. Should not use accessors or other methods.
  */

shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h

@@ -212,10 +212,6 @@ typedef NS_ENUM(NSInteger, FlutterAppExitResponse) {
 - (void)announceAccessibilityMessage:(NSString*)message
                         withPriority:(NSAccessibilityPriorityLevel)priority;
 
-- (void)onVSyncWithTimestamp:(CFTimeInterval)timestamp
-             targetTimestamp:(CFTimeInterval)targetTimestamp
-                       baton:(uintptr_t)baton;
-
 @end
 
 @interface FlutterEngine (Tests)

shell/platform/darwin/macos/framework/Source/FlutterVSyncWaiter.mm

@@ -136,6 +136,9 @@ - (void)waitForVSync:(uintptr_t)baton {
 }
 
 - (void)dealloc {
+  if (_pending_baton.has_value()) {
+    FML_LOG(WARNING) << "Deallocating FlutterVSyncWaiter with a pending vsync";
+  }
   [_displayLink invalidate];
 }
 

shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h

@@ -67,8 +67,6 @@
  */
 - (void)updateSemantics:(nonnull const FlutterSemanticsUpdate2*)update;
 
-- (void)waitForVSync:(uintptr_t)baton;
-
 @end
 
 // Private methods made visible for testing