[ios] Animate user dot between user location updates

Use UIView animation to explicitly animate the user dot between user location updates. There is a tricky special case, which is that the callout must point to the annotation view’s implicit frame but must quickly rendezvous with the explicit frame.

Fixes #1041.

4 files changed, 91 insertions, 20 deletions

diff --git a/platform/ios/CHANGELOG.md b/platform/ios/CHANGELOG.md
index a5e8916c99..887802928d 100644
--- a/platform/ios/CHANGELOG.md
+++ b/platform/ios/CHANGELOG.md
@@ -6,6 +6,7 @@ Mapbox welcomes participation and contributions from everyone.  If you’d like
 
 - Applications linking against the SDK static framework no longer need to add `-ObjC` to the Other Linker Flags (`OTHER_LDFLAGS`) build setting. If you previously added this flag solely for this SDK, removing the flag may potentially reduce the overall size of your application. ([#4641](https://github.com/mapbox/mapbox-gl-native/pull/4641))
 - Removed the `armv7s` slice from the SDK to reduce its size. iPhone 5 and iPhone 5c automatically use the `armv7` slice instead. ([#4641](https://github.com/mapbox/mapbox-gl-native/pull/4641))
+- The user dot now moves smoothly between user location updates while user location tracking is disabled. ([#1582](https://github.com/mapbox/mapbox-gl-native/pull/1582))
 - User location heading updates now resume properly when an app becomes active again. ([#4674](https://github.com/mapbox/mapbox-gl-native/pull/4674))
 - A more specific user agent string is now sent with style and tile requests. ([#4012](https://github.com/mapbox/mapbox-gl-native/pull/4012))
 - Removed unused SVG files from the SDK’s resource bundle. ([#4641](https://github.com/mapbox/mapbox-gl-native/pull/4641))
diff --git a/platform/ios/app/MBXCustomCalloutView.m b/platform/ios/app/MBXCustomCalloutView.m
index 8f9bd8ed40..11ce86e76a 100644
--- a/platform/ios/app/MBXCustomCalloutView.m
+++ b/platform/ios/app/MBXCustomCalloutView.m
@@ -40,6 +40,11 @@ static CGFloat const tipWidth = 10.0;
 
 - (void)presentCalloutFromRect:(CGRect)rect inView:(UIView *)view constrainedToView:(UIView *)constrainedView animated:(BOOL)animated
 {
+    if ([self.delegate respondsToSelector:@selector(calloutViewWillAppear:)])
+    {
+        [self.delegate performSelector:@selector(calloutViewWillAppear:) withObject:self];
+    }
+    
     [view addSubview:self];
     // prepare title label
     if ([self.representedObject respondsToSelector:@selector(title)])
diff --git a/platform/ios/include/MGLCalloutView.h b/platform/ios/include/MGLCalloutView.h
index 8e72ee9d68..59f52adb6d 100644
--- a/platform/ios/include/MGLCalloutView.h
+++ b/platform/ios/include/MGLCalloutView.h
@@ -62,6 +62,11 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)calloutViewTapped:(UIView<MGLCalloutView> *)calloutView;
 
+/**
+ Called before the callout view appears on screen, or before the appearance animation will start.
+ */
+- (void)calloutViewWillAppear:(UIView<MGLCalloutView> *)calloutView;
+
 @end
 
 NS_ASSUME_NONNULL_END
\ No newline at end of file
diff --git a/platform/ios/src/MGLMapView.mm b/platform/ios/src/MGLMapView.mm
index 195635ef1d..a3db891efa 100644
--- a/platform/ios/src/MGLMapView.mm
+++ b/platform/ios/src/MGLMapView.mm
@@ -200,6 +200,8 @@ public:
     /// Size of the rectangle formed by unioning the maximum slop area around every annotation image.
     CGSize _unionedAnnotationImageSize;
     std::vector<MGLAnnotationTag> _annotationsNearbyLastTap;
+    CGPoint _initialImplicitCalloutViewOffset;
+    NSDate *_userLocationAnimationCompletionDate;
 
     BOOL _isWaitingForRedundantReachableNotification;
     BOOL _isTargetingInterfaceBuilder;
@@ -1268,21 +1270,14 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
 
     CGPoint tapPoint = [singleTap locationInView:self];
 
-    if (self.userLocationVisible)
+    if (self.userLocationVisible
+        && [self.userLocationAnnotationView.layer.presentationLayer hitTest:tapPoint])
     {
-        // Assume that the user is fat-fingering an annotation.
-        CGRect hitRect = CGRectInset({ tapPoint, CGSizeZero },
-                                     -MGLAnnotationImagePaddingForHitTest,
-                                     -MGLAnnotationImagePaddingForHitTest);
-
-        if (CGRectIntersectsRect(hitRect, self.userLocationAnnotationView.frame))
+        if ( ! _userLocationAnnotationIsSelected)
         {
-            if ( ! _userLocationAnnotationIsSelected)
-            {
-                [self selectAnnotation:self.userLocation animated:YES];
-            }
-            return;
+            [self selectAnnotation:self.userLocation animated:YES];
         }
+        return;
     }
     
     MGLAnnotationTag hitAnnotationTag = [self annotationTagAtPoint:tapPoint persistingResults:YES];
@@ -2830,9 +2825,12 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
 
         if (_userLocationAnnotationIsSelected)
         {
-            positioningRect = CGRectInset(self.userLocationAnnotationView.frame,
-                                          -MGLAnnotationImagePaddingForCallout,
-                                          -MGLAnnotationImagePaddingForCallout);
+            positioningRect = [self.userLocationAnnotationView.layer.presentationLayer frame];
+            
+            CGRect implicitAnnotationFrame = [self.userLocationAnnotationView.layer.presentationLayer frame];
+            CGRect explicitAnnotationFrame = self.userLocationAnnotationView.frame;
+            _initialImplicitCalloutViewOffset = CGPointMake(CGRectGetMinX(explicitAnnotationFrame) - CGRectGetMinX(implicitAnnotationFrame),
+                                                            CGRectGetMinY(explicitAnnotationFrame) - CGRectGetMinY(implicitAnnotationFrame));
         }
 
         // consult delegate for left and/or right accessory views
@@ -2940,7 +2938,7 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
 {
     if ( ! annotation) return;
 
-    if ([self.selectedAnnotation isEqual:annotation])
+    if (self.selectedAnnotation == annotation)
     {
         // dismiss popup
         [self.calloutViewForSelectedAnnotation dismissCalloutAnimated:animated];
@@ -2957,6 +2955,35 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     }
 }
 
+- (void)calloutViewWillAppear:(UIView <MGLCalloutView> *)calloutView
+{
+    if (_userLocationAnnotationIsSelected ||
+        CGPointEqualToPoint(_initialImplicitCalloutViewOffset, CGPointZero))
+    {
+        return;
+    }
+    
+    // The user location callout view initially points to the user location
+    // annotation’s implicit (visual) frame, which is offset from the
+    // annotation’s explicit frame. Now the callout view needs to rendezvous
+    // with the explicit frame. Then,
+    // -updateUserLocationAnnotationViewAnimatedWithDuration: will take over the
+    // next time an updated location arrives.
+    [UIView animateWithDuration:_userLocationAnimationCompletionDate.timeIntervalSinceNow
+                          delay:0
+                        options:(UIViewAnimationOptionCurveLinear |
+                                 UIViewAnimationOptionAllowUserInteraction |
+                                 UIViewAnimationOptionBeginFromCurrentState)
+                     animations:^
+     {
+         calloutView.frame = CGRectOffset(calloutView.frame,
+                                          _initialImplicitCalloutViewOffset.x,
+                                          _initialImplicitCalloutViewOffset.y);
+         _initialImplicitCalloutViewOffset = CGPointZero;
+     }
+                     completion:NULL];
+}
+
 - (void)showAnnotations:(NS_ARRAY_OF(id <MGLAnnotation>) *)annotations animated:(BOOL)animated
 {
     CGFloat maximumPadding = 100;
@@ -3269,7 +3296,12 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     self.userLocationAnnotationView.haloLayer.hidden = ! CLLocationCoordinate2DIsValid(self.userLocation.coordinate) ||
         newLocation.horizontalAccuracy > 10;
 
-    [self updateUserLocationAnnotationView];
+    NSTimeInterval duration = MGLAnimationDuration;
+    if (oldLocation && ! CGPointEqualToPoint(self.userLocationAnnotationView.center, CGPointZero))
+    {
+        duration = MAX([newLocation.timestamp timeIntervalSinceDate:oldLocation.timestamp], MGLUserLocationAnimationDuration);
+    }
+    [self updateUserLocationAnnotationViewAnimatedWithDuration:duration];
 }
 
 - (void)didUpdateLocationWithUserTrackingAnimated:(BOOL)animated
@@ -3710,14 +3742,17 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
 
 - (void)updateUserLocationAnnotationView
 {
+    [self updateUserLocationAnnotationViewAnimatedWithDuration:0];
+}
+
+- (void)updateUserLocationAnnotationViewAnimatedWithDuration:(NSTimeInterval)duration
+{
     MGLUserLocationAnnotationView *annotationView = self.userLocationAnnotationView;
     if ( ! CLLocationCoordinate2DIsValid(self.userLocation.coordinate)) {
         annotationView.hidden = YES;
         return;
     }
 
-    if ( ! annotationView.superview) [self.glView addSubview:annotationView];
-
     CGPoint userPoint;
     if (self.userTrackingMode != MGLUserTrackingModeNone
         && self.userTrackingState == MGLUserTrackingStateChanged)
@@ -3728,11 +3763,36 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     {
         userPoint = [self convertCoordinate:self.userLocation.coordinate toPointToView:self];
     }
+    
+    if ( ! annotationView.superview)
+    {
+        [self.glView addSubview:annotationView];
+        // Prevents the view from sliding in from the origin.
+        annotationView.center = userPoint;
+    }
 
     if (CGRectContainsPoint(CGRectInset(self.bounds, -MGLAnnotationUpdateViewportOutset.width,
         -MGLAnnotationUpdateViewportOutset.height), userPoint))
     {
-        annotationView.center = userPoint;
+        // Smoothly move the user location annotation view and callout view to
+        // the new location.
+        [UIView animateWithDuration:duration
+                              delay:0
+                            options:(UIViewAnimationOptionCurveLinear |
+                                     UIViewAnimationOptionAllowUserInteraction |
+                                     UIViewAnimationOptionBeginFromCurrentState)
+                         animations:^{
+            if (self.selectedAnnotation == self.userLocation)
+            {
+                UIView <MGLCalloutView> *calloutView = self.calloutViewForSelectedAnnotation;
+                calloutView.frame = CGRectOffset(calloutView.frame,
+                                                 userPoint.x - annotationView.center.x,
+                                                 userPoint.y - annotationView.center.y);
+            }
+            annotationView.center = userPoint;
+        } completion:NULL];
+        _userLocationAnimationCompletionDate = [NSDate dateWithTimeIntervalSinceNow:duration];
+        
         annotationView.hidden = NO;
         [annotationView setupLayers];