Implement map projection functionality (#254)

* Implement map projection functionality

* Add missing MGL_EXPORT

* Remove the automatic copyright header

src/mbgl/map/map.cpp

@@ -426,6 +426,12 @@ std::vector<LatLng> Map::latLngsForPixels(const std::vector<ScreenCoordinate>& s
     return ret;
 }
 
+#pragma mark - Transform
+
+TransformState Map::getTransfromState() const {
+    return impl->transform.getState();
+}
+
 #pragma mark - Annotations
 
 void Map::addAnnotationImage(std::unique_ptr<style::Image> image) {

src/mbgl/map/map_impl.hpp

@@ -76,4 +76,9 @@ public:
     std::unique_ptr<StillImageRequest> stillImageRequest;
 };
 
+// Forward declaration of this method is required for the MapProjection class
+CameraOptions cameraForLatLngs(const std::vector<LatLng>& latLngs,
+                               const Transform& transform,
+                               const EdgeInsets& padding);
+
 } // namespace mbgl

src/mbgl/map/map_projection.cpp

@@ -0,0 +1,39 @@
+#include <mbgl/map/map_projection.hpp>
+#include <mbgl/map/map_impl.hpp>
+#include <mbgl/map/transform.hpp>
+
+namespace mbgl {
+
+MapProjection::MapProjection(const Map& map)
+    : transform(std::make_unique<Transform>(map.getTransfromState())) {}
+
+MapProjection::~MapProjection() = default;
+
+ScreenCoordinate MapProjection::pixelForLatLng(const LatLng& latLng) const {
+    // The implementation is just a copy from map.cpp
+    LatLng unwrappedLatLng = latLng.wrapped();
+    unwrappedLatLng.unwrapForShortestPath(transform->getLatLng());
+    return transform->latLngToScreenCoordinate(unwrappedLatLng);
+}
+
+LatLng MapProjection::latLngForPixel(const ScreenCoordinate& pixel) const {
+    // The implementation is just a copy from map.cpp
+    return transform->screenCoordinateToLatLng(pixel);
+}
+
+void MapProjection::setCamera(const CameraOptions& camera) {
+    transform->jumpTo(camera);
+}
+
+CameraOptions MapProjection::getCamera() const {
+    return transform->getCameraOptions(nullopt);
+}
+
+void MapProjection::setVisibleCoordinates(const std::vector<LatLng>& latLngs,
+                                          const EdgeInsets& padding) {
+    transform->jumpTo(mbgl::cameraForLatLngs(latLngs, *transform, padding)
+                      .withBearing(-transform->getBearing() * util::RAD2DEG)
+                      .withPitch(transform->getPitch() * util::RAD2DEG));
+}
+
+} // namespace mbgl