[core] Ignore shortest path when gesturing in Transform::easeTo

If gesture in progress, we transfer the world rounds from the end
longitude into start, so we can guarantee the "scroll effect" of
rounding the world while assuring the end longitude remains wrapped.
Otherwise, find the shortest path.

1 files changed, 9 insertions, 3 deletions

diff --git a/src/mbgl/map/transform.cpp b/src/mbgl/map/transform.cpp
index 29fa7c9eb2..b283251431 100644
--- a/src/mbgl/map/transform.cpp
+++ b/src/mbgl/map/transform.cpp
@@ -77,7 +77,8 @@ void Transform::jumpTo(const CameraOptions& camera) {
  * not included in `options`.
  */
 void Transform::easeTo(const CameraOptions& camera, const AnimationOptions& animation) {
-    const LatLng latLng = camera.center.value_or(getLatLng()).wrapped();
+    const LatLng unwrappedLatLng = camera.center.value_or(getLatLng());
+    const LatLng latLng = unwrappedLatLng.wrapped();
     double zoom = camera.zoom.value_or(getZoom());
     double angle = camera.angle.value_or(getAngle());
     double pitch = camera.pitch.value_or(getPitch());
@@ -89,8 +90,13 @@ void Transform::easeTo(const CameraOptions& camera, const AnimationOptions& anim
     // Determine endpoints.
     EdgeInsets padding;
     if (camera.padding) padding = *camera.padding;
-    LatLng startLatLng = getLatLng(padding).wrapped();
-    startLatLng.unwrapForShortestPath(latLng);
+    LatLng startLatLng = getLatLng(padding);
+    // If gesture in progress, we transfer the world rounds from the end
+    // longitude into start, so we can guarantee the "scroll effect" of rounding
+    // the world while assuring the end longitude remains wrapped.
+    if (isGestureInProgress()) startLatLng.longitude -= unwrappedLatLng.longitude - latLng.longitude;
+    // Find the shortest path otherwise.
+    else startLatLng.unwrapForShortestPath(latLng);
 
     const ScreenCoordinate startPoint = {
         state.lngX(startLatLng.longitude),