[core] Move TransformState::worldSize() to Projection

include/mbgl/util/projection.hpp

@@ -8,14 +8,20 @@
 
 namespace mbgl {
 
+// Spherical Mercator projection
+// http://docs.openlayers.org/library/spherical_mercator.html
 class Projection {
-
 public:
+    // Map pixel width at given scale.
+    static double worldSize(double scale) {
+        return scale * util::tileSize;
+    }
+
     static double getMetersPerPixelAtLatitude(double lat, double zoom) {
         const double constrainedZoom = util::clamp(zoom, util::MIN_ZOOM, util::MAX_ZOOM);
-        const double mapPixelWidthAtZoom = std::pow(2.0, constrainedZoom) * util::tileSize;
+        const double constrainedScale = std::pow(2.0, constrainedZoom);
         const double constrainedLatitude = util::clamp(lat, -util::LATITUDE_MAX, util::LATITUDE_MAX);
-        return std::cos(constrainedLatitude * util::DEG2RAD) * util::M2PI * util::EARTH_RADIUS_M / mapPixelWidthAtZoom;
+        return std::cos(constrainedLatitude * util::DEG2RAD) * util::M2PI * util::EARTH_RADIUS_M / worldSize(constrainedScale);
     }
 
     static ProjectedMeters projectedMetersForLatLng(const LatLng& latLng) {
@@ -32,7 +38,7 @@ public:
     }
 
     static LatLng latLngForProjectedMeters(const ProjectedMeters& projectedMeters) {
-        double latitude = (2 * std::atan(std::exp(projectedMeters.northing / util::EARTH_RADIUS_M)) - (M_PI / 2)) * util::RAD2DEG;
+        double latitude = (2 * std::atan(std::exp(projectedMeters.northing / util::EARTH_RADIUS_M)) - (M_PI / 2.0)) * util::RAD2DEG;
         double longitude = projectedMeters.easting * util::RAD2DEG / util::EARTH_RADIUS_M;
 
         latitude = util::clamp(latitude, -util::LATITUDE_MAX, util::LATITUDE_MAX);

src/mbgl/map/transform.cpp

@@ -7,6 +7,7 @@
 #include <mbgl/util/unitbezier.hpp>
 #include <mbgl/util/interpolate.hpp>
 #include <mbgl/util/chrono.hpp>
+#include <mbgl/util/projection.hpp>
 #include <mbgl/math/clamp.hpp>
 #include <mbgl/platform/log.hpp>
 #include <mbgl/platform/platform.hpp>
@@ -131,8 +132,8 @@ void Transform::easeTo(const CameraOptions& camera, const AnimationOptions& anim
 
     Duration duration = animation.duration ? *animation.duration : Duration::zero();
 
-    const double startWorldSize = state.worldSize();
     const double startScale = state.scale;
+    const double startWorldSize = Projection::worldSize(startScale);
     const double startAngle = state.angle;
     const double startPitch = state.pitch;
     state.panning = latLng != startLatLng;
@@ -288,8 +289,7 @@ void Transform::flyTo(const CameraOptions &camera, const AnimationOptions &anima
         return;
     }
 
-    const double startWorldSize = state.worldSize();
-
+    const double startWorldSize = Projection::worldSize(state.scale);
     state.panning = true;
     state.scaling = true;
     state.rotating = angle != startAngle;

src/mbgl/map/transform_state.cpp

@@ -17,7 +17,7 @@ TransformState::TransformState(ConstrainMode constrainMode_, ViewportMode viewpo
 
 void TransformState::matrixFor(mat4& matrix, const UnwrappedTileID& tileID) const {
     const uint64_t tileScale = 1ull << tileID.canonical.z;
-    const double s = worldSize() / tileScale;
+    const double s = Projection::worldSize(scale) / tileScale;
 
     matrix::identity(matrix);
     matrix::translate(matrix, matrix,
@@ -108,12 +108,12 @@ LatLng TransformState::getLatLng(LatLng::WrapMode wrapMode) const {
 }
 
 double TransformState::pixel_x() const {
-    const double center = (width - worldSize()) / 2;
+    const double center = (width - Projection::worldSize(scale)) / 2;
     return center + x;
 }
 
 double TransformState::pixel_y() const {
-    const double center = (height - worldSize()) / 2;
+    const double center = (height - Projection::worldSize(scale)) / 2;
     return center + y;
 }
 
@@ -205,7 +205,7 @@ Point<double> TransformState::project(const LatLng& ll) const {
     return Point<double>(
         (util::LONGITUDE_MAX + ll.longitude),
         (util::LONGITUDE_MAX - util::RAD2DEG * std::log(std::tan(M_PI / 4 + ll.latitude * M_PI / util::DEGREES_MAX)))
-    ) * worldSize() / util::DEGREES_MAX;
+    ) * Projection::worldSize(scale) / util::DEGREES_MAX;
 }
 
 LatLng TransformState::unproject(const Point<double>& p, double worldSize, LatLng::WrapMode wrapMode) const {
@@ -225,10 +225,6 @@ double TransformState::scaleZoom(double s) const {
     return util::log2(s);
 }
 
-double TransformState::worldSize() const {
-    return scale * util::tileSize;
-}
-
 ScreenCoordinate TransformState::latLngToScreenCoordinate(const LatLng& latLng) const {
     if (width == 0 || height == 0) {
         return {};
@@ -284,7 +280,7 @@ LatLng TransformState::screenCoordinateToLatLng(const ScreenCoordinate& point, L
 mat4 TransformState::coordinatePointMatrix(double z) const {
     mat4 proj;
     getProjMatrix(proj);
-    float s = worldSize() / std::pow(2, z);
+    float s = Projection::worldSize(scale) / std::pow(2, z);
     matrix::scale(proj, proj, s, s, 1);
     matrix::multiply(proj, getPixelMatrix(), proj);
     return proj;
@@ -328,7 +324,7 @@ void TransformState::moveLatLng(const LatLng& latLng, const ScreenCoordinate& an
     auto centerCoord = project(getLatLng(LatLng::Unwrapped));
     auto latLngCoord = project(latLng);
     auto anchorCoord = project(screenCoordinateToLatLng(anchor));
-    setLatLngZoom(unproject(centerCoord + latLngCoord - anchorCoord, worldSize()), getZoom());
+    setLatLngZoom(unproject(centerCoord + latLngCoord - anchorCoord, Projection::worldSize(scale)), getZoom());
 }
 
 void TransformState::setLatLngZoom(const LatLng &latLng, double zoom) {
@@ -355,8 +351,8 @@ void TransformState::setScalePoint(const double newScale, const ScreenCoordinate
     scale = constrainedScale;
     x = constrainedPoint.x;
     y = constrainedPoint.y;
-    Bc = worldSize() / util::DEGREES_MAX;
-    Cc = worldSize() / util::M2PI;
+    Bc = Projection::worldSize(scale) / util::DEGREES_MAX;
+    Cc = Projection::worldSize(scale) / util::M2PI;
 }
 
 } // namespace mbgl

src/mbgl/map/transform_state.hpp

@@ -4,6 +4,7 @@
 #include <mbgl/util/geo.hpp>
 #include <mbgl/util/geometry.hpp>
 #include <mbgl/util/constants.hpp>
+#include <mbgl/util/projection.hpp>
 #include <mbgl/util/mat4.hpp>
 
 #include <cstdint>
@@ -88,8 +89,6 @@ private:
     // logical dimensions
     uint16_t width = 0, height = 0;
 
-    double worldSize() const;
-
     mat4 coordinatePointMatrix(double z) const;
     mat4 getPixelMatrix() const;
 
@@ -117,8 +116,8 @@ private:
     double pitch = 0.0;
 
     // cache values for spherical mercator math
-    double Bc = worldSize() / util::DEGREES_MAX;
-    double Cc = worldSize() / util::M2PI;
+    double Bc = Projection::worldSize(scale) / util::DEGREES_MAX;
+    double Cc = Projection::worldSize(scale) / util::M2PI;
 };
 
 } // namespace mbgl