[ios] Added teardown of core objects when receiving UIApplicationWill…

…TerminateNotification (#13367)

platform/darwin/src/MGLMapSnapshotter.h

@@ -173,14 +173,16 @@ typedef void (^MGLMapSnapshotCompletionHandler)(MGLMapSnapshot* _Nullable snapsh
 MGL_EXPORT
 @interface MGLMapSnapshotter : NSObject
 
+- (instancetype)init NS_UNAVAILABLE;
+
 /**
  Initializes and returns a map snapshotter object that produces snapshots
  according to the given options.
  
  @param options The options to use when generating a map snapshot.
  @return An initialized map snapshotter.
  */
-- (instancetype)initWithOptions:(MGLMapSnapshotOptions *)options;
+- (instancetype)initWithOptions:(MGLMapSnapshotOptions *)options NS_DESIGNATED_INITIALIZER;
 
 /**
  Starts the snapshot creation and executes the specified block with the result.

platform/darwin/src/MGLMapSnapshotter.mm

@@ -117,6 +117,7 @@ - (CLLocationCoordinate2D)coordinateForPoint:(NSPoint)point
 
 @interface MGLMapSnapshotter()
 @property (nonatomic) BOOL cancelled;
+@property (nonatomic) BOOL terminated;
 @property (nonatomic) dispatch_queue_t resultQueue;
 @property (nonatomic, copy) MGLMapSnapshotCompletionHandler completion;
 + (void)completeWithErrorCode:(MGLErrorCode)errorCode description:(nonnull NSString*)description onQueue:(dispatch_queue_t)queue completion:(MGLMapSnapshotCompletionHandler)completion;
@@ -129,6 +130,8 @@ @implementation MGLMapSnapshotter {
 }
 
 - (void)dealloc {
+    [[NSNotificationCenter defaultCenter] removeObserver:self];
+
     if (_completion) {
         MGLAssert(_snapshotCallback, @"Snapshot in progress - there should be a valid callback");
 
@@ -139,16 +142,41 @@ - (void)dealloc {
     }
 }
 
+
+- (instancetype)init {
+    NSAssert(NO, @"Please use -[MGLMapSnapshotter initWithOptions:]");
+    [super doesNotRecognizeSelector:_cmd];
+    return nil;
+}
+
 - (instancetype)initWithOptions:(MGLMapSnapshotOptions *)options
 {
     MGLLogDebug(@"Initializing withOptions: %@", options);
     self = [super init];
     if (self) {
         [self setOptions:options];
+#if TARGET_OS_IPHONE
+        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillTerminate:) name:UIApplicationWillTerminateNotification object:nil];
+#else
+        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillTerminate:) name:NSApplicationWillTerminateNotification object:nil];
+#endif
     }
     return self;
 }
 
+- (void)applicationWillTerminate:(NSNotification *)notification
+{
+    if (self.completion) {
+        [self cancel];
+    }
+
+    _mbglMapSnapshotter.reset();
+    _snapshotCallback.reset();
+    _mbglThreadPool.reset();
+
+    self.terminated = YES;
+}
+
 - (void)startWithCompletionHandler:(MGLMapSnapshotCompletionHandler)completion
 {
     MGLLogDebug(@"Starting withCompletionHandler: %@", completion);
@@ -167,7 +195,12 @@ - (void)startWithQueue:(dispatch_queue_t)queue completionHandler:(MGLMapSnapshot
         [NSException raise:NSInternalInconsistencyException
                     format:@"Already started this snapshotter."];
     }
-
+
+    if (self.terminated) {
+        [NSException raise:NSInternalInconsistencyException
+                    format:@"Starting a snapshotter after application termination is not supported."];
+    }
+
     self.completion = completion;
     self.resultQueue = queue;
     self.cancelled = NO;
@@ -539,7 +572,18 @@ + (void)completeWithErrorCode:(MGLErrorCode)errorCode description:(nonnull NSStr
 
 - (void)setOptions:(MGLMapSnapshotOptions *)options
 {
+    if (_terminated) {
+        [NSException raise:NSInternalInconsistencyException
+                    format:@"Calling MGLMapSnapshotter.options after application termination is not supported."];
+    }
+
     MGLLogDebug(@"Setting options: %@", options);
+
+    if (_completion) {
+        [self cancel];
+    }
+
+    _cancelled = NO;
     _options = options;
     mbgl::DefaultFileSource *mbglFileSource = [MGLOfflineStorage sharedOfflineStorage].mbglFileSource;
     _mbglThreadPool = mbgl::sharedThreadPool();

platform/ios/CHANGELOG.md

@@ -9,6 +9,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 * Added `MGLLoggingConfiguration` and `MGLLoggingBlockHandler` that handle error and fault events produced by the SDK. ([#13235](https://github.com/mapbox/mapbox-gl-native/pull/13235))
 * This SDK’s dynamic framework now has a bundle identifier of `com.mapbox.Mapbox`. ([#12857](https://github.com/mapbox/mapbox-gl-native/pull/12857))
 * Modified the behavior of the map view so that programmatic camera transitions can no longer be interrupted by user interaction when `MGLMapView.zoomEnabled`, `MGLMapView.rotateEnabled`, `MGLMapView.scrollEnabled`, and `MGLMapView.pitchEnabled` are set to false. ([#13362](https://github.com/mapbox/mapbox-gl-native/pull/13362))
+* Fixed random crashes during app termination. ([#13367](https://github.com/mapbox/mapbox-gl-native/pull/13367))
 * Added `-[MGLStyle removeSource:error:]` that returns a `BOOL` indicating success (and an optional `NSError` in case of failure). ([#13399](https://github.com/mapbox/mapbox-gl-native/pull/13399))
 
 ## 4.6.0 - November 7, 2018

platform/ios/app/MBXViewController.m

@@ -1986,7 +1986,7 @@ - (MGLAnnotationView *)mapView:(MGLMapView *)mapView viewForAnnotation:(id<MGLAn
         annotationView.backgroundColor = [UIColor whiteColor];
 
         // Note that having two long press gesture recognizers on overlapping
-        // views (`self.view` & `annotationView`) will cause weird behaviour.
+        // views (`self.view` & `annotationView`) will cause weird behavior.
         // Comment out the pin dropping functionality in the handleLongPress:
         // method in this class to make draggable annotation views play nice.
         annotationView.draggable = YES;

platform/ios/src/MGLMapView.h

@@ -636,11 +636,14 @@ MGL_EXPORT IB_DESIGNABLE
 
  Changing the center coordinate centers the map on the new coordinate without
  changing the current zoom level.
-
+ 
  @param coordinate The new center coordinate for the map.
  @param animated Specify `YES` if you want the map view to scroll to the new
     location or `NO` if you want the map to display the new location
     immediately.
+ 
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`.
  */
 - (void)setCenterCoordinate:(CLLocationCoordinate2D)coordinate animated:(BOOL)animated;
 
@@ -653,6 +656,9 @@ MGL_EXPORT IB_DESIGNABLE
  @param animated Specify `YES` if you want the map view to animate scrolling and
     zooming to the new location or `NO` if you want the map to display the new
     location immediately.
+ 
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`.
  */
 - (void)setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate zoomLevel:(double)zoomLevel animated:(BOOL)animated;
 
@@ -667,6 +673,9 @@ MGL_EXPORT IB_DESIGNABLE
  @param animated Specify `YES` if you want the map view to animate scrolling,
     zooming, and rotating to the new location or `NO` if you want the map to
     display the new location immediately.
+ 
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`.
  */
 - (void)setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate zoomLevel:(double)zoomLevel direction:(CLLocationDirection)direction animated:(BOOL)animated;
 
@@ -682,6 +691,9 @@ MGL_EXPORT IB_DESIGNABLE
     zooming, and rotating to the new location or `NO` if you want the map to
     display the new location immediately.
  @param completion The block executed after the animation finishes.
+ 
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`.
  */
 - (void)setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate zoomLevel:(double)zoomLevel direction:(CLLocationDirection)direction animated:(BOOL)animated completionHandler:(nullable void (^)(void))completion;
 
@@ -1020,6 +1032,10 @@ MGL_EXPORT IB_DESIGNABLE
     bounds with zoom level as high (close to the ground) as possible while still
     including the entire coordinate bounds. The camera object uses the current
     direction and pitch.
+
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`; you may receive a `nil` return value
+ depending on the order of notification delivery.
  */
 - (MGLMapCamera *)cameraThatFitsCoordinateBounds:(MGLCoordinateBounds)bounds;
 
@@ -1034,6 +1050,10 @@ MGL_EXPORT IB_DESIGNABLE
     with zoom level as high (close to the ground) as possible while still
     including the entire coordinate bounds. The camera object uses the current
     direction and pitch.
+ 
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`; you may receive a `nil` return value
+ depending on the order of notification delivery.
  */
 - (MGLMapCamera *)cameraThatFitsCoordinateBounds:(MGLCoordinateBounds)bounds edgePadding:(UIEdgeInsets)insets;
 
@@ -1050,6 +1070,10 @@ MGL_EXPORT IB_DESIGNABLE
     with zoom level as high (close to the ground) as possible while still
     including the entire coordinate bounds. The initial camera's pitch and
     direction will be honored.
+
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`; you may receive a `nil` return value
+ depending on the order of notification delivery.
  */
 - (MGLMapCamera *)camera:(MGLMapCamera *)camera fittingCoordinateBounds:(MGLCoordinateBounds)bounds edgePadding:(UIEdgeInsets)insets;
 
@@ -1065,6 +1089,10 @@ MGL_EXPORT IB_DESIGNABLE
  @return A camera object centered on the shape's center with zoom level as high
     (close to the ground) as possible while still including the entire shape. The
     initial camera's pitch and direction will be honored.
+ 
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`; you may receive a `nil` return value
+ depending on the order of notification delivery.
  */
 - (MGLMapCamera *)camera:(MGLMapCamera *)camera fittingShape:(MGLShape *)shape edgePadding:(UIEdgeInsets)insets;
 
@@ -1079,6 +1107,10 @@ MGL_EXPORT IB_DESIGNABLE
  @return A camera object centered on the shape's center with zoom level as high 
     (close to the ground) as possible while still including the entire shape. The
     camera object uses the current pitch.
+ 
+ @note The behavior of this method is undefined if called in response to
+ `UIApplicationWillTerminateNotification`; you may receive a `nil` return value
+ depending on the order of notification delivery.
  */
 - (MGLMapCamera *)cameraThatFitsShape:(MGLShape *)shape direction:(CLLocationDirection)direction edgePadding:(UIEdgeInsets)insets;