Transform::flyTo invalid zoom checks

src/mbgl/map/transform.cpp

@@ -293,6 +293,11 @@ void Transform::flyTo(const CameraOptions &camera, const AnimationOptions &anima
         Point<double> framePoint = util::interpolate(startPoint, endPoint, us);
         double frameZoom = startZoom + state.scaleZoom(1 / w(s));
 
+        // Zoom can be NaN if size is empty.
+        if (std::isnan(frameZoom)) {
+            frameZoom = zoom;
+        }
+
         // Convert to geographic coordinates and set the new viewpoint.
         LatLng frameLatLng = Projection::unproject(framePoint, startScale);
         state.setLatLngZoom(frameLatLng, frameZoom);

src/mbgl/map/transform_state.cpp

@@ -358,7 +358,7 @@ void TransformState::setLatLngZoom(const LatLng& latLng, double zoom) {
         constrained = bounds->constrain(latLng);
     }
 
-    double newScale = zoomScale(zoom);
+    double newScale = util::clamp(zoomScale(zoom), min_scale, max_scale);
     const double newWorldSize = newScale * util::tileSize;
     Bc = newWorldSize / util::DEGREES_MAX;
     Cc = newWorldSize / util::M2PI;

test/map/transform.test.cpp

@@ -28,6 +28,27 @@ TEST(Transform, InvalidZoom) {
     ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
     ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
     ASSERT_DOUBLE_EQ(1, transform.getZoom());
+
+    transform.setZoom(transform.getState().getMaxZoom() + 0.1);
+    ASSERT_DOUBLE_EQ(transform.getZoom(), transform.getState().getMaxZoom());
+
+    CameraOptions cameraOptions;
+    cameraOptions.center = LatLng { util::LATITUDE_MAX, util::LONGITUDE_MAX };
+    cameraOptions.zoom = transform.getState().getMaxZoom();
+
+    // Executing flyTo with an empty size causes frameZoom to be NaN.
+    transform.flyTo(cameraOptions);
+    transform.updateTransitions(transform.getTransitionStart() + transform.getTransitionDuration());
+    ASSERT_DOUBLE_EQ(transform.getZoom(), transform.getState().getMaxZoom());
+
+    // Executing flyTo with maximum zoom level to the same zoom level causes
+    // frameZoom to be bigger than maximum zoom.
+    transform.resize(Size { 100, 100 });
+    transform.flyTo(cameraOptions);
+    transform.updateTransitions(transform.getTransitionStart() + transform.getTransitionDuration());
+
+    ASSERT_TRUE(transform.getState().valid());
+    ASSERT_DOUBLE_EQ(transform.getState().getMaxZoom(), transform.getZoom());
 }