[ios] Avoid jumping when setting user tracking mode

Account for the user dot’s alignment when flying to the initial user location. Previously, during incremental location updates, we relied on a hack in which the edge insets resulted in a 0×0 viewport, forcing the center upward or downward. But flyTo() relies on the viewport’s size to control the trajectory. So instead, all location updates now use a correctly-sized viewport centered on the offset user dot.

Pushed the user dot farther away from the view edges.

Programmatic rotation and compass rotation are now centered on the user dot even if it’s aligned at the top or bottom. Previously, pressing the compass would trigger a rotation centered on the center of the view.

1 files changed, 42 insertions, 24 deletions

diff --git a/platform/ios/src/MGLMapView.mm b/platform/ios/src/MGLMapView.mm
index 0e9b1ccf4a..959e1e7be0 100644
--- a/platform/ios/src/MGLMapView.mm
+++ b/platform/ios/src/MGLMapView.mm
@@ -67,6 +67,10 @@ const NSTimeInterval MGLAnimationDuration = 0.3;
 /// match a typical interval between user location updates.
 const NSTimeInterval MGLUserLocationAnimationDuration = 1.0;
 
+/// Distance between the map view’s edge and that of the user location
+/// annotation view.
+const CGFloat MGLUserLocationAnnotationViewPadding = 50;
+
 const CGSize MGLAnnotationUpdateViewportOutset = {150, 150};
 const CGFloat MGLMinimumZoom = 3;
 
@@ -1893,10 +1897,19 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     _mbglMap->cancelTransitions();
 
     CGFloat duration = animated ? MGLAnimationDuration : 0;
-
-    _mbglMap->setBearing(direction,
-                         MGLEdgeInsetsFromNSEdgeInsets(self.contentInset),
-                         MGLDurationInSeconds(duration));
+    
+    if (self.userTrackingMode == MGLUserTrackingModeNone)
+    {
+        _mbglMap->setBearing(direction,
+                             MGLEdgeInsetsFromNSEdgeInsets(self.contentInset),
+                             MGLDurationInSeconds(duration));
+    }
+    else
+    {
+        CGPoint centerPoint = self.userLocationAnnotationViewCenter;
+        _mbglMap->setBearing(direction, { centerPoint.x, centerPoint.y },
+                             MGLDurationInSeconds(duration));
+    }
 }
 
 - (void)setDirection:(CLLocationDirection)direction
@@ -1950,7 +1963,7 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
         return;
     }
 
-    mbgl::CameraOptions cameraOptions = [self cameraOptionsObjectForAnimatingToCamera:camera];
+    mbgl::CameraOptions cameraOptions = [self cameraOptionsObjectForAnimatingToCamera:camera edgePadding:self.contentInset];
     mbgl::AnimationOptions animationOptions;
     if (duration > 0)
     {
@@ -1985,10 +1998,10 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
 {
     self.userTrackingMode = MGLUserTrackingModeNone;
     
-    [self _flyToCamera:camera withDuration:duration peakAltitude:peakAltitude completionHandler:completion];
+    [self _flyToCamera:camera edgePadding:self.contentInset withDuration:duration peakAltitude:peakAltitude completionHandler:completion];
 }
 
-- (void)_flyToCamera:(MGLMapCamera *)camera withDuration:(NSTimeInterval)duration peakAltitude:(CLLocationDistance)peakAltitude completionHandler:(nullable void (^)(void))completion
+- (void)_flyToCamera:(MGLMapCamera *)camera edgePadding:(UIEdgeInsets)insets withDuration:(NSTimeInterval)duration peakAltitude:(CLLocationDistance)peakAltitude completionHandler:(nullable void (^)(void))completion
 {
     _mbglMap->cancelTransitions();
     if ([self.camera isEqual:camera])
@@ -1996,7 +2009,7 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
         return;
     }
 
-    mbgl::CameraOptions cameraOptions = [self cameraOptionsObjectForAnimatingToCamera:camera];
+    mbgl::CameraOptions cameraOptions = [self cameraOptionsObjectForAnimatingToCamera:camera edgePadding:insets];
     mbgl::AnimationOptions animationOptions;
     if (duration >= 0)
     {
@@ -2025,14 +2038,14 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
 
 /// Returns a CameraOptions object that specifies parameters for animating to
 /// the given camera.
-- (mbgl::CameraOptions)cameraOptionsObjectForAnimatingToCamera:(MGLMapCamera *)camera
+- (mbgl::CameraOptions)cameraOptionsObjectForAnimatingToCamera:(MGLMapCamera *)camera edgePadding:(UIEdgeInsets)insets
 {
     mbgl::CameraOptions options;
     if (CLLocationCoordinate2DIsValid(camera.centerCoordinate))
     {
         options.center = MGLLatLngFromLocationCoordinate2D(camera.centerCoordinate);
     }
-    options.padding = MGLEdgeInsetsFromNSEdgeInsets(self.contentInset);
+    options.padding = MGLEdgeInsetsFromNSEdgeInsets(insets);
     options.zoom = MGLZoomLevelForAltitude(camera.altitude, camera.pitch,
                                            camera.centerCoordinate.latitude,
                                            self.frame.size);
@@ -3058,7 +3071,6 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
             if (self.zoomLevel < self.currentMinimumZoom)
             {
                 [self setZoomLevel:self.currentMinimumZoom animated:YES];
-                _userTrackingMode = MGLUserTrackingModeFollowWithHeading; // reapply
             }
 
             if (self.userLocationAnnotationView)
@@ -3119,12 +3131,6 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
         }
     }
 
-    CLLocationDirection course = self.userLocation.location.course;
-    if (course < 0 || self.userTrackingMode != MGLUserTrackingModeFollowWithCourse)
-    {
-        course = -1;
-    }
-
     if (self.userTrackingMode != MGLUserTrackingModeNone)
     {
         // center on user location unless we're already centered there (or very close)
@@ -3134,6 +3140,21 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
 
         if (std::abs(currentPoint.x - correctPoint.x) > 1.0 || std::abs(currentPoint.y - correctPoint.y) > 1.0)
         {
+            CLLocationDirection course = self.userLocation.location.course;
+            if (course < 0 || self.userTrackingMode != MGLUserTrackingModeFollowWithCourse)
+            {
+                course = -1;
+            }
+            
+            // Shift the center point upward or downward to accommodate a
+            // shifted user location annotation view.
+            CGRect bounds = self.bounds;
+            CGRect boundsAroundCorrectPoint = CGRectOffset(bounds,
+                                                           correctPoint.x - CGRectGetMidX(bounds),
+                                                           correctPoint.y - CGRectGetMidY(bounds));
+            UIEdgeInsets insets = UIEdgeInsetsMake(CGRectGetMinY(boundsAroundCorrectPoint) - CGRectGetMinY(bounds), 0,
+                                                   CGRectGetMaxY(bounds) - CGRectGetMaxY(boundsAroundCorrectPoint), 0);
+            
             if (self.zoomLevel >= MGLMinimumZoomLevelForUserTracking)
             {
                 // at sufficient detail, just re-center the map; don't zoom
@@ -3141,9 +3162,6 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
                 if (self.userTrackingState == MGLUserTrackingStateChanged)
                 {
                     // Ease incrementally to the new user location.
-                    UIEdgeInsets insets = UIEdgeInsetsMake(correctPoint.y, correctPoint.x,
-                                                           CGRectGetHeight(self.bounds) - correctPoint.y,
-                                                           CGRectGetWidth(self.bounds) - correctPoint.x);
                     CAMediaTimingFunction *linearFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
                     [self _setCenterCoordinate:self.userLocation.location.coordinate
                                    edgePadding:insets
@@ -3164,7 +3182,7 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
                     camera.heading = course;
                     
                     __weak MGLMapView *weakSelf = self;
-                    [self _flyToCamera:camera withDuration:animated ? -1 : 0 peakAltitude:-1 completionHandler:^{
+                    [self _flyToCamera:camera edgePadding:insets withDuration:animated ? -1 : 0 peakAltitude:-1 completionHandler:^{
                         MGLMapView *strongSelf = weakSelf;
                         strongSelf.userTrackingState = MGLUserTrackingStateChanged;
                     }];
@@ -3184,7 +3202,7 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
                                                           self.frame.size);
                 
                 __weak MGLMapView *weakSelf = self;
-                [self _flyToCamera:camera withDuration:animated ? -1 : 0 peakAltitude:-1 completionHandler:^{
+                [self _flyToCamera:camera edgePadding:insets withDuration:animated ? -1 : 0 peakAltitude:-1 completionHandler:^{
                     MGLMapView *strongSelf = weakSelf;
                     strongSelf.userTrackingState = MGLUserTrackingStateChanged;
                 }];
@@ -3519,10 +3537,10 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
         case MGLAnnotationVerticalAlignmentCenter:
             break;
         case MGLAnnotationVerticalAlignmentTop:
-            center.y = CGRectGetHeight(self.userLocationAnnotationView.frame);
+            center.y = CGRectGetHeight(self.userLocationAnnotationView.frame) + MGLUserLocationAnnotationViewPadding;
             break;
         case MGLAnnotationVerticalAlignmentBottom:
-            center.y = CGRectGetHeight(contentFrame) - CGRectGetHeight(self.userLocationAnnotationView.frame);
+            center.y = CGRectGetHeight(contentFrame) - CGRectGetHeight(self.userLocationAnnotationView.frame) - MGLUserLocationAnnotationViewPadding;
             break;
     }