[ios] Improve tilt gesture recognizer detection.

platform/ios/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 Mapbox welcomes participation and contributions from everyone. Please read [CONTRIBUTING.md](../../CONTRIBUTING.md) to get started.
 
+## master
+
+* Fixed an issue that caused tilt gesture to trigger easily. ([#15349](https://github.com/mapbox/mapbox-gl-native/pull/15349))
+
 ## 5.3.0
 
 This release changes how offline tile requests are billed — they are now billed on a pay-as-you-go basis and all developers are able raise the offline tile limit for their users. Offline requests were previously exempt from monthly active user (MAU) billing and increasing the offline per-user tile limit to more than 6,000 tiles required the purchase of an enterprise license. By upgrading to this release, you are opting into the changes outlined in [this blog post](https://blog.mapbox.com/offline-maps-for-all-bb0fc51827be) and [#15380](https://github.com/mapbox/mapbox-gl-native/pull/15380).

platform/ios/src/MGLMapView.mm

@@ -267,6 +267,9 @@ @interface MGLMapView () <UIGestureRecognizerDelegate,
 @property (nonatomic) MGLMapDebugMaskOptions residualDebugMask;
 @property (nonatomic, copy) NSURL *residualStyleURL;
 
+/// Tilt gesture recognizer helper
+@property (nonatomic, assign) CGPoint dragGestureMiddlePoint;
+
 - (mbgl::Map &)mbglMap;
 
 @end
@@ -2139,6 +2142,9 @@ - (void)handleTwoFingerDragGesture:(UIPanGestureRecognizer *)twoFingerDrag
 
     if (twoFingerDrag.state == UIGestureRecognizerStateBegan)
     {
+        CGPoint midPoint = [twoFingerDrag translationInView:twoFingerDrag.view];
+        // Creates an angle at the beginning of the gesture
+        self.dragGestureMiddlePoint = CGPointMake(midPoint.x, midPoint.y-1);
         initialPitch = *self.mbglMap.getCameraOptions().pitch;
         [self notifyGestureDidBegin];
     }
@@ -2150,30 +2156,45 @@ - (void)handleTwoFingerDragGesture:(UIPanGestureRecognizer *)twoFingerDrag
             twoFingerDrag.state = UIGestureRecognizerStateEnded;
             return;
         }
-
-        CGFloat gestureDistance = CGPoint([twoFingerDrag translationInView:twoFingerDrag.view]).y;
-        CGFloat slowdown = 2.0;
-
-        CGFloat pitchNew = initialPitch - (gestureDistance / slowdown);
-
-        CGPoint centerPoint = [self anchorPointForGesture:twoFingerDrag];
-
-        MGLMapCamera *oldCamera = self.camera;
-        MGLMapCamera *toCamera = [self cameraByTiltingToPitch:pitchNew];
-
-        if ([self _shouldChangeFromCamera:oldCamera toCamera:toCamera])
-        {
-            self.mbglMap.jumpTo(mbgl::CameraOptions()
+
+        CGPoint west = [twoFingerDrag locationOfTouch:0 inView:twoFingerDrag.view];
+        CGPoint east = [twoFingerDrag locationOfTouch:1 inView:twoFingerDrag.view];
+        CLLocationDegrees fingerSlopeAngle = [self angleBetweenPoints:west endPoint:east];
+
+        CGPoint middlePoint = [twoFingerDrag translationInView:twoFingerDrag.view];
+
+        CLLocationDegrees gestureSlopeAngle = [self angleBetweenPoints:self.dragGestureMiddlePoint endPoint:middlePoint];
+        self.dragGestureMiddlePoint = middlePoint;
+        if (fabs(fingerSlopeAngle) < 45 && fabs(gestureSlopeAngle) > 60 ) {
+
+            CGFloat gestureDistance = CGPoint([twoFingerDrag translationInView:twoFingerDrag.view]).y;
+            CGFloat slowdown = 2.0;
+
+            CGFloat pitchNew = initialPitch - (gestureDistance / slowdown);
+
+            CGPoint centerPoint = [self anchorPointForGesture:twoFingerDrag];
+
+            MGLMapCamera *oldCamera = self.camera;
+            MGLMapCamera *toCamera = [self cameraByTiltingToPitch:pitchNew];
+
+            if ([self _shouldChangeFromCamera:oldCamera toCamera:toCamera])
+            {
+                self.mbglMap.jumpTo(mbgl::CameraOptions()
                                     .withPitch(pitchNew)
                                     .withAnchor(mbgl::ScreenCoordinate { centerPoint.x, centerPoint.y }));
+            }
+
+            [self cameraIsChanging];
+
         }
 
-        [self cameraIsChanging];
+
     }
     else if (twoFingerDrag.state == UIGestureRecognizerStateEnded || twoFingerDrag.state == UIGestureRecognizerStateCancelled)
     {
         [self notifyGestureDidEndWithDrift:NO];
         [self unrotateIfNeededForGesture];
+        self.dragGestureMiddlePoint = CGPointZero;
     }
 
 }
@@ -2296,7 +2317,7 @@ - (void)calloutViewDidAppear:(UIView<MGLCalloutView> *)calloutView
 
 - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
 {
-    if ([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]])
+    if (gestureRecognizer == _twoFingerDrag)
     {
         UIPanGestureRecognizer *panGesture = (UIPanGestureRecognizer *)gestureRecognizer;
 
@@ -2305,14 +2326,9 @@ - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
             CGPoint west = [panGesture locationOfTouch:0 inView:panGesture.view];
             CGPoint east = [panGesture locationOfTouch:1 inView:panGesture.view];
 
-            if (west.x > east.x) {
-                CGPoint swap = west;
-                west = east;
-                east = swap;
-            }
-
-            CLLocationDegrees horizontalToleranceDegrees = 60.0;
-            if ([self angleBetweenPoints:west east:east] > horizontalToleranceDegrees) {
+            CLLocationDegrees horizontalToleranceDegrees = 45.0;
+            CLLocationDegrees degrees = [self angleBetweenPoints:west endPoint:east];
+            if (fabs(degrees) > horizontalToleranceDegrees) {
                 return NO;
             }
         }
@@ -2334,16 +2350,22 @@ - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
 - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
 {
     NSArray *validSimultaneousGestures = @[ self.pan, self.pinch, self.rotate ];
-
     return ([validSimultaneousGestures containsObject:gestureRecognizer] && [validSimultaneousGestures containsObject:otherGestureRecognizer]);
 }
 
-- (CLLocationDegrees)angleBetweenPoints:(CGPoint)west east:(CGPoint)east
+- (CLLocationDegrees)angleBetweenPoints:(CGPoint)originPoint endPoint:(CGPoint)endPoint
 {
-    CGFloat slope = (west.y - east.y) / (west.x - east.x);
+    if (originPoint.x > endPoint.x) {
+        CGPoint swap = originPoint;
+        originPoint = endPoint;
+        endPoint = swap;
+    }
+
+    CGFloat x = (endPoint.x - originPoint.x);
+    CGFloat y = (endPoint.y - originPoint.y);
 
-    CGFloat angle = atan(fabs(slope));
-    CLLocationDegrees degrees = MGLDegreesFromRadians(angle);
+    CGFloat radians = atan2(y, x);
+    CLLocationDegrees degrees = MGLDegreesFromRadians(radians);
 
     return degrees;
 }

platform/ios/test/MGLMapViewPitchTests.m

@@ -2,23 +2,35 @@
 #import <XCTest/XCTest.h>
 
 @interface MockUIPanGestureRecognizer : UIPanGestureRecognizer
-@property CGFloat mbx_tiltGestureYTranslation;
 @property NSUInteger mbx_numberOfFingersForGesture;
+@property CGPoint mbx_middlePoint;
+@property CGPoint mbx_westPoint;
+@property CGPoint mbx_eastPoint;
 @end
 
 @implementation MockUIPanGestureRecognizer
 - (instancetype)initWithTarget:(id)target action:(SEL)action {
     if (self = [super initWithTarget:target action:action]) {
-        self.mbx_tiltGestureYTranslation = 0;
         self.mbx_numberOfFingersForGesture = 2;
+        self.mbx_westPoint = CGPointMake(100, 0);
+        self.mbx_eastPoint = CGPointMake(200, 0);
     }
     return self;
 }
 - (NSUInteger)numberOfTouches { return self.mbx_numberOfFingersForGesture; }
-- (CGPoint)translationInView:(UIView *)view { return CGPointMake(0, self.mbx_tiltGestureYTranslation); }
+- (CGPoint)translationInView:(UIView *)view { return self.mbx_middlePoint; }
+- (CGPoint)locationOfTouch:(NSUInteger)touchIndex inView:(UIView *)view {
+    if (touchIndex == 0) {
+        return self.mbx_westPoint;
+    }
+    return self.mbx_eastPoint;
+}
 - (void)setTiltGestureYTranslationForPitchDegrees:(CGFloat)degrees {
     // The tilt gesture takes the number of screen points the fingers have moved and then divides them by a "slowdown" factor, which happens to be set to 2.0 in -[MGLMapView handleTwoFingerDragGesture:].
-    self.mbx_tiltGestureYTranslation = -(degrees * 2.0);
+    CGFloat mbx_tiltGestureYTranslation = -(degrees * 2.0);
+    self.mbx_westPoint = CGPointMake(self.mbx_westPoint.x, mbx_tiltGestureYTranslation);
+    self.mbx_eastPoint = CGPointMake(self.mbx_eastPoint.x, mbx_tiltGestureYTranslation);
+    self.mbx_middlePoint = CGPointMake(self.mbx_middlePoint.x, mbx_tiltGestureYTranslation);
 }
 @end
 
@@ -112,6 +124,25 @@ - (void)testTiltGesture {
     }
 }
 
+- (void)testHorizontalTiltGesture {
+    MockUIPanGestureRecognizer *gesture = [[MockUIPanGestureRecognizer alloc] initWithTarget:self.mapView action:nil];
+    gesture.state = UIGestureRecognizerStateBegan;
+    [self.mapView handleTwoFingerDragGesture:gesture];
+    XCTAssertEqual(self.mapView.camera.pitch, 0, @"Pitch should initially be set to 0°.");
+
+    // Tilt gestures should not be triggered on horizontal dragging.
+    for (NSInteger deltaX = 0; deltaX < 5; deltaX++) {
+        gesture.mbx_westPoint = CGPointMake(100 - deltaX, 100);
+        gesture.mbx_eastPoint = CGPointMake(100 - deltaX, 50);
+        gesture.mbx_middlePoint = CGPointMake((gesture.mbx_westPoint.x + gesture.mbx_westPoint.x)/2, (gesture.mbx_westPoint.y + gesture.mbx_westPoint.y)/2);
+
+        gesture.state = UIGestureRecognizerStateChanged;
+
+        [self.mapView handleTwoFingerDragGesture:gesture];
+        XCTAssertEqual(self.mapView.camera.pitch, 0, @"Horizontal dragging should not tilt the map.");
+    }
+}
+
 - (void)testTiltGestureFromInitialTilt {
     CGFloat initialTilt = 20;
     CGFloat additionalTilt = 30;