[ios] Added "pending" completion blocks - to ensure that (for example) annotation views are in the position they are expected to be at the end of an animation.

Author: Julian Rex

platform/ios/src/MGLMapView.mm

@@ -247,6 +247,7 @@ @interface MGLMapView () <UIGestureRecognizerDelegate,
 @property (nonatomic) NSMutableDictionary<NSString *, NSMutableArray<MGLAnnotationView *> *> *annotationViewReuseQueueByIdentifier;
 @property (nonatomic, readonly) BOOL enablePresentsWithTransaction;
 @property (nonatomic) UIImage *lastSnapshotImage;
+@property (nonatomic) NSMutableArray *pendingCompletionBlocks;
 
 /// Experimental rendering performance measurement.
 @property (nonatomic) BOOL experimental_enableFrameRateMeasurement;
@@ -612,6 +613,11 @@ - (void)commonInit
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didEnterBackground:) name:UIApplicationDidEnterBackgroundNotification object:nil];
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(willEnterForeground:) name:UIApplicationWillEnterForegroundNotification object:nil];
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didBecomeActive:) name:UIApplicationDidBecomeActiveNotification object:nil];
+
+    // Pending completion blocks are called *after* annotation views have been updated
+    // in updateFromDisplayLink.
+    _pendingCompletionBlocks = [NSMutableArray array];
+    
 
     // As of 3.7.5, we intentionally do not listen for `UIApplicationWillResignActiveNotification` or call `pauseRendering:` in response to it, as doing
     // so causes a loop when asking for location permission. See: https://github.com/mapbox/mapbox-gl-native/issues/11225
@@ -1033,6 +1039,33 @@ - (CGPoint)contentCenter
     return CGPointMake(CGRectGetMidX(contentFrame), CGRectGetMidY(contentFrame));
 }
 
+#pragma mark - Pending completion blocks
+
+- (void)processPendingBlocks
+{
+    NSArray *blocks = self.pendingCompletionBlocks;
+    self.pendingCompletionBlocks = [NSMutableArray array];
+
+    for (dispatch_block_t block in blocks)
+    {
+        block();
+    }
+}
+
+- (BOOL)addPendingBlock:(dispatch_block_t)block
+{
+    // Only add a block if the display link (that calls processPendingBlocks) is
+    // running, otherwise fall back to calling immediately.
+    BOOL addBlock = (_displayLink && !_displayLink.isPaused);
+    
+    if (addBlock)
+    {
+        [self.pendingCompletionBlocks addObject:block];
+    }
+
+    return addBlock;
+}
+
 #pragma mark - Life Cycle -
 
 - (void)updateFromDisplayLink:(CADisplayLink *)displayLink
@@ -1057,7 +1090,7 @@ - (void)updateFromDisplayLink:(CADisplayLink *)displayLink
         return;
     }
 
-    if (_needsDisplayRefresh)
+    if (_needsDisplayRefresh || (self.pendingCompletionBlocks.count > 0))
     {
         _needsDisplayRefresh = NO;
 
@@ -1066,6 +1099,13 @@ - (void)updateFromDisplayLink:(CADisplayLink *)displayLink
         [self updateAnnotationViews];
         [self updateCalloutView];
 
+        // Call any pending completion blocks. This is primarily to ensure
+        // that annotations are in the expected position after core rendering
+        // and map update.
+        //
+        // TODO: Consider using this same mechanism for delegate callbacks.
+        [self processPendingBlocks];
+        
         _mbglView->display();
     }
 
@@ -1132,6 +1172,7 @@ - (void)validateDisplayLink
     {
         [_displayLink invalidate];
         _displayLink = nil;
+        [self processPendingBlocks];
     }
 }
 
@@ -1415,6 +1456,7 @@ - (void)pauseRendering:(__unused NSNotification *)notification
         [MGLMapboxEvents flush];
 
         _displayLink.paused = YES;
+        [self processPendingBlocks];
 
         if ( ! self.glSnapshotView)
         {
@@ -1467,6 +1509,11 @@ - (void)setHidden:(BOOL)hidden
 {
     super.hidden = hidden;
     _displayLink.paused = hidden;
+    
+    if (hidden)
+    {
+        [self processPendingBlocks];
+    }
 }
 
 - (void)tintColorDidChange
@@ -3188,26 +3235,35 @@ - (void)_setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate edgePaddin
         animationOptions.duration.emplace(MGLDurationFromTimeInterval(duration));
         animationOptions.easing.emplace(MGLUnitBezierForMediaTimingFunction(function));
     }
+    
+    dispatch_block_t pendingCompletion;
+    
     if (completion)
     {
-        animationOptions.transitionFinishFn = [completion]() {
+        __weak __typeof__(self) weakSelf = self;
+        
+        pendingCompletion = ^{
+            if (![weakSelf addPendingBlock:completion])
+            {
+                completion();
+            }
+        };
+        
+        animationOptions.transitionFinishFn = [pendingCompletion]() {
             // Must run asynchronously after the transition is completely over.
             // Otherwise, a call to -setCenterCoordinate: within the completion
             // handler would reenter the completion handler’s caller.
-            dispatch_async(dispatch_get_main_queue(), ^{
-                completion();
-            });
+
+            dispatch_async(dispatch_get_main_queue(), pendingCompletion);
         };
     }
 
     MGLMapCamera *camera = [self cameraForCameraOptions:cameraOptions];
     if ([self.camera isEqualToMapCamera:camera] && UIEdgeInsetsEqualToEdgeInsets(_contentInset, insets))
     {
-        if (completion)
+        if (pendingCompletion)
         {
-            [self animateWithDelay:duration animations:^{
-                completion();
-            }];
+            [self animateWithDelay:duration animations:pendingCompletion];
         }
         return;
     }
@@ -3374,12 +3430,22 @@ - (void)_setVisibleCoordinates:(const CLLocationCoordinate2D *)coordinates count
         animationOptions.duration.emplace(MGLDurationFromTimeInterval(duration));
         animationOptions.easing.emplace(MGLUnitBezierForMediaTimingFunction(function));
     }
+    
+    dispatch_block_t pendingCompletion;
+    
     if (completion)
     {
-        animationOptions.transitionFinishFn = [completion]() {
-            dispatch_async(dispatch_get_main_queue(), ^{
+        __weak __typeof__(self) weakSelf = self;
+        
+        pendingCompletion = ^{
+            if (![weakSelf addPendingBlock:completion])
+            {
                 completion();
-            });
+            }
+        };
+
+        animationOptions.transitionFinishFn = [pendingCompletion]() {
+            dispatch_async(dispatch_get_main_queue(), pendingCompletion);
         };
     }
 
@@ -3389,11 +3455,9 @@ - (void)_setVisibleCoordinates:(const CLLocationCoordinate2D *)coordinates count
     MGLMapCamera *camera = [self cameraForCameraOptions:cameraOptions];
     if ([self.camera isEqualToMapCamera:camera])
     {
-        if (completion)
+        if (pendingCompletion)
         {
-            [self animateWithDelay:duration animations:^{
-                completion();
-            }];
+            [self animateWithDelay:duration animations:pendingCompletion];
         }
         return;
     }
@@ -3534,22 +3598,30 @@ - (void)setCamera:(MGLMapCamera *)camera withDuration:(NSTimeInterval)duration a
         animationOptions.duration.emplace(MGLDurationFromTimeInterval(duration));
         animationOptions.easing.emplace(MGLUnitBezierForMediaTimingFunction(function));
     }
+    
+    dispatch_block_t pendingCompletion;
+    
     if (completion)
     {
-        animationOptions.transitionFinishFn = [completion]() {
-            dispatch_async(dispatch_get_main_queue(), ^{
+        __weak __typeof__(self) weakSelf = self;
+        
+        pendingCompletion = ^{
+            if (![weakSelf addPendingBlock:completion])
+            {
                 completion();
-            });
+            }
+        };
+
+        animationOptions.transitionFinishFn = [pendingCompletion]() {
+            dispatch_async(dispatch_get_main_queue(), pendingCompletion);
         };
     }
 
     if ([self.camera isEqualToMapCamera:camera] && UIEdgeInsetsEqualToEdgeInsets(_contentInset, edgePadding))
     {
-        if (completion)
+        if (pendingCompletion)
         {
-            [self animateWithDelay:duration animations:^{
-                completion();
-            }];
+            [self animateWithDelay:duration animations:pendingCompletion];
         }
         return;
     }
@@ -3605,22 +3677,30 @@ - (void)_flyToCamera:(MGLMapCamera *)camera edgePadding:(UIEdgeInsets)insets wit
         animationOptions.minZoom = MGLZoomLevelForAltitude(peakAltitude, peakPitch,
                                                            peakLatitude, self.frame.size);
     }
+    
+    dispatch_block_t pendingCompletion;
+    
     if (completion)
     {
-        animationOptions.transitionFinishFn = [completion]() {
-            dispatch_async(dispatch_get_main_queue(), ^{
+        __weak __typeof__(self) weakSelf = self;
+        
+        pendingCompletion = ^{
+            if (![weakSelf addPendingBlock:completion])
+            {
                 completion();
-            });
+            }
+        };
+
+        animationOptions.transitionFinishFn = [pendingCompletion]() {
+            dispatch_async(dispatch_get_main_queue(), pendingCompletion);
         };
     }
 
     if ([self.camera isEqualToMapCamera:camera] && UIEdgeInsetsEqualToEdgeInsets(_contentInset, insets))
     {
-        if (completion)
+        if (pendingCompletion)
         {
-            [self animateWithDelay:duration animations:^{
-                completion();
-            }];
+            [self animateWithDelay:duration animations:pendingCompletion];
         }
         return;
     }