[core] Camera center and anchor points are mutually exclusive

2 files changed, 21 insertions, 1 deletions

diff --git a/src/mbgl/map/transform.cpp b/src/mbgl/map/transform.cpp
index 9b2e2a7812..4b82a51fac 100644
--- a/src/mbgl/map/transform.cpp
+++ b/src/mbgl/map/transform.cpp
@@ -554,7 +554,10 @@ void Transform::startTransition(const CameraOptions& camera,
     observer.onCameraWillChange(isAnimated ? MapObserver::CameraChangeMode::Animated : MapObserver::CameraChangeMode::Immediate);
 
     // Associate the anchor, if given, with a coordinate.
-    optional<ScreenCoordinate> anchor = camera.anchor;
+    // Anchor and center points are mutually exclusive, with preference for the center point when
+    // both camera options are present.
+    assert(!camera.anchor || !camera.center);
+    optional<ScreenCoordinate> anchor = camera.center ? nullopt : camera.anchor;
     LatLng anchorLatLng;
     if (anchor) {
         anchor->y = state.size.height - anchor->y;
diff --git a/test/map/transform.test.cpp b/test/map/transform.test.cpp
index 44b5f49366..ed923d85c0 100644
--- a/test/map/transform.test.cpp
+++ b/test/map/transform.test.cpp
@@ -476,6 +476,23 @@ TEST(Transform, Camera) {
     transform.updateTransitions(transform.getTransitionStart() + Milliseconds(750));
     transform.updateTransitions(transform.getTransitionStart() + transform.getTransitionDuration());
     ASSERT_FALSE(transform.inTransition());
+
+    // Anchor and center points are mutually exclusive.
+    CameraOptions camera;
+    camera.center = LatLng { 0, 0 };
+    camera.anchor = ScreenCoordinate { 0, 0 }; // top-left
+    camera.zoom = transform.getState().getMaxZoom();
+#ifndef NDEBUG
+    ASSERT_DEATH(transform.jumpTo(camera), R"test(!camera.anchor \|\| !camera.center)test");
+#else
+    transform.easeTo(camera, AnimationOptions(Seconds(1)));
+    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(250));
+    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(500));
+    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(750));
+    transform.updateTransitions(transform.getTransitionStart() + transform.getTransitionDuration());
+    ASSERT_DOUBLE_EQ(transform.getLatLng().latitude(), 0);
+    ASSERT_DOUBLE_EQ(transform.getLatLng().longitude(), 0);
+#endif // NDEBUG
 }
 
 TEST(Transform, DefaultTransform) {