Possible to set zoom beyond maximum limit

[friedbunny]

When setting the zoom level programmatically, Transform::setLatLngZoom and the subsequent Transform::_setScaleXY do not check if the zoom level is sane.

In iOS, it's possible to set mapView.zoomLevel = 21.f and it will render the map, even though the maximum zoom level via gestures is z18. Values higher than 21.9f break rendering but are settable. Using a zoom gesture will pop the map back to z18.

Here is one solution that works, but I get the feeling that Transform::_setScaleXY is the right place to do this, not Transform::setLatLng:

diff --git a/src/mbgl/map/transform.cpp b/src/mbgl/map/transform.cpp
index 6c0f136..95448a7 100644
--- a/src/mbgl/map/transform.cpp
+++ b/src/mbgl/map/transform.cpp
@@ -118,7 +118,7 @@ void Transform::setLatLng(const LatLng latLng, const Duration duration) {
 void Transform::setLatLngZoom(const LatLng latLng, const double zoom, const Duration duration) {
     std::lock_guard<std::recursive_mutex> lock(mtx);

-    double new_scale = std::pow(2.0, zoom);
+    double new_scale = std::pow(2.0, std::fmin(std::fmax(zoom, getMinZoom()), getMaxZoom()));

     const double s = new_scale * util::tileSize;
     current.Bc = s / 360;

/cc @kkaefer

[friedbunny]

Let's link this thread up with the ability to customize the max zoom, #509.

[1ec5]

This is now addressed by copious use of TransformState::constrain() (#3026).