Adds a delegate to notify when a gesture is canceled.

platform/ios/CHANGELOG.md

@@ -21,6 +21,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 * Fixed an issue where an `MGLMapSnapshotOptions` with an invalid `MGLMapCamera.centerCoordinate`, negative `MGLMapCamera.heading`, negative `MGLMapCamera.pitch`, and negative `MGLMapSnapshotOptions.zoomLevel` resulted in a snapshot centered on Null Island at zoom level 0 even if the style specified a different initial center coordinate or zoom level. ([#280](https://github.com/mapbox/mapbox-gl-native-ios/pull/280))
 * Fixed an error that occurred if your implementation of the `-[MGLOfflineStorageDelegate offlineStorage:URLForResourceOfKind:]` method returned a local file URL. ([mapbox/mapbox-gl-native#16428](https://github.com/mapbox/mapbox-gl-native/pull/16428)) 
 * Certain logging statements no longer run on the main thread. ([mapbox/mapbox-gl-native#16325](https://github.com/mapbox/mapbox-gl-native/pull/16325))
+* Added the `-[MGLMapViewDelegate mapView:didCancelGestureForCamera:]` delegate method, which offers an opportunity to take action when the map canceled a gesture. ([#284](https://github.com/mapbox/mapbox-gl-native-ios/pull/284))
 
 ## 5.8.0
 

platform/ios/app/MBXViewController.m

@@ -2229,6 +2229,12 @@ - (BOOL)mapView:(MGLMapView *)mapView shouldChangeFromCamera:(MGLMapCamera *)old
     }
 }
 
+- (void)mapView:(MGLMapView *)mapView didCancelGestureForCamera:(MGLMapCamera *)camera {
+    MGLMapCamera *toCamera = self.mapView.camera;
+    toCamera.centerCoordinate = CLLocationCoordinate2DMake(39.748947, -104.995882);
+    [self.mapView flyToCamera:toCamera withDuration:2.0 completionHandler:nil];
+}
+
 - (void)mapViewRegionIsChanging:(MGLMapView *)mapView
 {
     [self updateHUD];

platform/ios/src/MGLMapView.mm

@@ -1778,6 +1778,10 @@ - (void)handlePanGesture:(UIPanGestureRecognizer *)pan
                    default:
                       self.mbglMap.moveBy({ offset.x, offset.y }, MGLDurationFromTimeInterval(self.decelerationRate));
                 }
+            } else {
+                if ([self.delegate respondsToSelector:@selector(mapView:didCancelGestureForCamera:)]) {
+                    [self.delegate mapView:self didCancelGestureForCamera:toCamera];
+                }
             }
         }
 
@@ -1869,8 +1873,8 @@ - (void)handlePinchGesture:(UIPinchGestureRecognizer *)pinch
         // Calculates the final camera zoom, this has no effect within current map camera.
         double zoom = log2(newScale);
         MGLMapCamera *toCamera = [self cameraByZoomingToZoomLevel:zoom aroundAnchorPoint:centerPoint];
-
-        if ( ! [self _shouldChangeFromCamera:oldCamera toCamera:toCamera])
+        BOOL shouldChange = [self _shouldChangeFromCamera:oldCamera toCamera:toCamera];
+        if ( ! shouldChange)
         {
             drift = NO;
         }
@@ -1886,6 +1890,9 @@ - (void)handlePinchGesture:(UIPinchGestureRecognizer *)pinch
         }
 
         self.isZooming = NO;
+        if ( !shouldChange && [self.delegate respondsToSelector:@selector(mapView:didCancelGestureForCamera:)]) {
+            [self.delegate mapView:self didCancelGestureForCamera:toCamera];
+        }
         [self notifyGestureDidEndWithDrift:drift];
         [self unrotateIfNeededForGesture];
     }
@@ -1999,6 +2006,10 @@ - (void)handleRotateGesture:(UIRotationGestureRecognizer *)rotate
                  {
                      [weakSelf unrotateIfNeededForGesture];
                  }];
+            } else {
+                if ([self.delegate respondsToSelector:@selector(mapView:didCancelGestureForCamera:)]) {
+                    [self.delegate mapView:self didCancelGestureForCamera:toCamera];
+                }
             }
         }
         else
@@ -2131,6 +2142,9 @@ - (void)handleDoubleTapGesture:(UITapGestureRecognizer *)doubleTap
     }
     else
     {
+        if ([self.delegate respondsToSelector:@selector(mapView:didCancelGestureForCamera:)]) {
+            [self.delegate mapView:self didCancelGestureForCamera:toCamera];
+        }
         [self unrotateIfNeededForGesture];
     }
 }
@@ -2169,6 +2183,10 @@ - (void)handleTwoFingerTapGesture:(UITapGestureRecognizer *)twoFingerTap
          {
              [weakSelf unrotateIfNeededForGesture];
          }];
+    } else {
+        if ([self.delegate respondsToSelector:@selector(mapView:didCancelGestureForCamera:)]) {
+            [self.delegate mapView:self didCancelGestureForCamera:toCamera];
+        }
     }
 }
 
@@ -2207,6 +2225,10 @@ - (void)handleQuickZoomGesture:(UILongPressGestureRecognizer *)quickZoom
                                 .withZoom(newZoom)
                                 .withAnchor(mbgl::ScreenCoordinate { centerPoint.x, centerPoint.y })
                                 .withPadding(MGLEdgeInsetsFromNSEdgeInsets(self.contentInset)));
+        } else {
+            if ([self.delegate respondsToSelector:@selector(mapView:didCancelGestureForCamera:)]) {
+                [self.delegate mapView:self didCancelGestureForCamera:toCamera];
+            }
         }
 
         [self cameraIsChanging];
@@ -2275,6 +2297,10 @@ - (void)handleTwoFingerDragGesture:(UIPanGestureRecognizer *)twoFingerDrag
                                     .withPitch(pitchNew)
                                     .withAnchor(mbgl::ScreenCoordinate { centerPoint.x, centerPoint.y })
                                     .withPadding(MGLEdgeInsetsFromNSEdgeInsets(self.contentInset)));
+            } else {
+                if ([self.delegate respondsToSelector:@selector(mapView:didCancelGestureForCamera:)]) {
+                    [self.delegate mapView:self didCancelGestureForCamera:toCamera];
+                }
             }
 
             [self cameraIsChanging];

platform/ios/src/MGLMapViewDelegate.h

@@ -75,6 +75,22 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (BOOL)mapView:(MGLMapView *)mapView shouldChangeFromCamera:(MGLMapCamera *)oldCamera toCamera:(MGLMapCamera *)newCamera reason:(MGLCameraChangeReason)reason;
 
+/**
+Tells the delegate that the map view canceled a gesture.
+
+This method is called as soon as `-mapView:shouldChangeFromCamera:toCamera:`
+returns `NO`.
+
+@param mapView The map view that the user is manipulating.
+@param camera The camera that triggered a gesture cancellation.
+
+#### Related examples
+See the <a href="https://docs.mapbox.com/ios/maps/examples/constraining-gestures/">
+Restrict map panning to an area</a> example to learn how to use this method
+and `MGLMapCamera` objects to restrict a users ability to pan your map.
+*/
+- (void)mapView:(MGLMapView *)mapView didCancelGestureForCamera:(MGLMapCamera *)camera;
+
 /**
  Tells the delegate that the viewpoint depicted by the map view is about to change.
 

platform/ios/test/MGLMapViewDelegateIntegrationTests.swift

@@ -95,6 +95,8 @@ extension MGLMapViewDelegateIntegrationTests: MGLMapViewDelegate {
 
     func mapView(_ mapView: MGLMapView, shouldChangeFrom oldCamera: MGLMapCamera, to newCamera: MGLMapCamera, reason: MGLCameraChangeReason) -> Bool { return false }
 
+    func mapView(_ mapView: MGLMapView, didCancelGestureFor camera: MGLMapCamera) {}
+
     func mapViewUserLocationAnchorPoint(_ mapView: MGLMapView) -> CGPoint { return CGPoint(x: 100, y: 100) }
 
     func mapView(_ mapView: MGLMapView, didFailToLoadImage imageName: String) -> UIImage? { return nil }