[core] add setMaxZoom, setMinZoom

also change the default maxZoom to 20 to match -js.

include/mbgl/map/map.hpp

@@ -116,7 +116,9 @@ public:
     CameraOptions cameraForLatLngBounds(const LatLngBounds&, const EdgeInsets&);
     CameraOptions cameraForLatLngs(const std::vector<LatLng>&, const EdgeInsets&);
     void resetZoom();
+    void setMinZoom(const double minZoom);
     double getMinZoom() const;
+    void setMaxZoom(const double maxZoom);
     double getMaxZoom() const;
 
     // Rotation

src/mbgl/map/map.cpp

@@ -303,10 +303,24 @@ void Map::resetZoom() {
     setZoom(0);
 }
 
+void Map::setMinZoom(const double minZoom) {
+    transform->setMinZoom(minZoom);
+    if (getZoom() < minZoom) {
+        setZoom(minZoom);
+    }
+}
+
 double Map::getMinZoom() const {
     return transform->getState().getMinZoom();
 }
 
+void Map::setMaxZoom(const double maxZoom) {
+    transform->setMaxZoom(maxZoom);
+    if (getZoom() > maxZoom) {
+        setZoom(maxZoom);
+    }
+}
+
 double Map::getMaxZoom() const {
     return transform->getState().getMaxZoom();
 }

src/mbgl/map/transform.cpp

@@ -465,6 +465,14 @@ void Transform::setScale(double scale, const EdgeInsets& padding, const Duration
     setScale(scale, center, duration);
 }
 
+void Transform::setMinZoom(const double minZoom) {
+    state.setMinZoom(minZoom);
+}
+
+void Transform::setMaxZoom(const double maxZoom) {
+    state.setMaxZoom(maxZoom);
+}
+
 #pragma mark - Angle
 
 void Transform::rotateBy(const PrecisionPoint& first, const PrecisionPoint& second, const Duration& duration) {

src/mbgl/map/transform.hpp

@@ -79,6 +79,9 @@ public:
     /** Returns the scale factor. */
     double getScale() const;
 
+    void setMinZoom(const double minZoom);
+    void setMaxZoom(const double maxZoom);
+
     // Angle
 
     void rotateBy(const PrecisionPoint& first, const PrecisionPoint& second, const Duration& = Duration::zero());

src/mbgl/map/transform_state.cpp

@@ -168,6 +168,10 @@ double TransformState::getScale() const {
     return scale;
 }
 
+void TransformState::setMinZoom(const double minZoom) {
+    min_scale = zoomScale(minZoom);
+}
+
 double TransformState::getMinZoom() const {
     double test_scale = min_scale;
     double unused_x = x;
@@ -177,6 +181,10 @@ double TransformState::getMinZoom() const {
     return scaleZoom(test_scale);
 }
 
+void TransformState::setMaxZoom(const double maxZoom) {
+    max_scale = zoomScale(maxZoom);
+}
+
 double TransformState::getMaxZoom() const {
     return scaleZoom(max_scale);
 }

src/mbgl/map/transform_state.hpp

@@ -52,7 +52,9 @@ public:
     int32_t getIntegerZoom() const;
     double getZoomFraction() const;
     double getScale() const;
+    void setMinZoom(const double minZoom);
     double getMinZoom() const;
+    void setMaxZoom(const double maxZoom);
     double getMaxZoom() const;
 
     // Rotation
@@ -83,7 +85,7 @@ private:
 
     // Limit the amount of zooming possible on the map.
     double min_scale = std::pow(2, 0);
-    double max_scale = std::pow(2, 18);
+    double max_scale = std::pow(2, 20);
 
     NorthOrientation orientation = NorthOrientation::Upwards;