Add LocationIndicatorLayer

New key is "G" in mbgl-glfw, cycling between no puck, centered
in the viewport and positioned in Tokyo.

1 files changed, 786 insertions, 0 deletions

diff --git a/src/mbgl/renderer/layers/render_location_indicator_layer.cpp b/src/mbgl/renderer/layers/render_location_indicator_layer.cpp
new file mode 100644
index 0000000000..20c3bb8cfe
--- /dev/null
+++ b/src/mbgl/renderer/layers/render_location_indicator_layer.cpp
@@ -0,0 +1,786 @@
+#include <array>
+#include <mapbox/cheap_ruler.hpp>
+#include <mbgl/gfx/backend_scope.hpp>
+#include <mbgl/gfx/renderer_backend.hpp>
+#include <mbgl/gl/context.hpp>
+#include <mbgl/gl/renderable_resource.hpp>
+#include <mbgl/map/transform_state.hpp>
+#include <mbgl/platform/gl_functions.hpp>
+#include <mbgl/renderer/bucket.hpp>
+#include <mbgl/renderer/layers/render_location_indicator_layer.hpp>
+#include <mbgl/renderer/paint_parameters.hpp>
+#include <mbgl/style/layers/location_indicator_layer.hpp>
+#include <mbgl/style/layers/location_indicator_layer_impl.hpp>
+#include <mbgl/style/layers/location_indicator_layer_properties.hpp>
+#include <mbgl/util/mat4.hpp>
+
+#include <mapbox/eternal.hpp>
+#include <mbgl/gl/context.hpp>
+#include <mbgl/gl/defines.hpp>
+#include <mbgl/gl/texture.hpp>
+#include <mbgl/gl/texture_resource.hpp>
+#include <mbgl/gl/types.hpp>
+#include <mbgl/platform/gl_functions.hpp>
+#include <mbgl/renderer/image_manager.hpp>
+
+using namespace mbgl::platform;
+namespace mbgl {
+
+struct LocationIndicatorRenderParameters {
+    LocationIndicatorRenderParameters() = default;
+    explicit LocationIndicatorRenderParameters(const TransformParameters& tp) : state(&tp.state) {}
+    LocationIndicatorRenderParameters(const LocationIndicatorRenderParameters& o) = default;
+    LocationIndicatorRenderParameters& operator=(const LocationIndicatorRenderParameters& o) = default;
+
+    double width = 0.0;
+    double height = 0.0;
+    double latitude = 0.0;
+    double longitude = 0.0;
+    double zoom = 0.0;
+    double bearing = 0.0;
+    double pitch = 0.0;
+    std::array<double, 16> projectionMatrix;
+    const TransformState* state = nullptr;
+    ImageManager* imageManager = nullptr;
+    // some testing defaults, for before it gets updated via props
+    double puckBearing = 0.0;
+    LatLng puckPosition = {0, 0};
+    double errorRadiusMeters;
+    mbgl::Color errorRadiusColor{0, 0, 0, 0};
+    mbgl::Color errorRadiusBorderColor{0, 0, 0, 0};
+    int puckSizePx = 0;
+    int puckHatSizePx = 0;
+    int puckShadowSizePx = 0;
+    float puckLayersDisplacement = 0;
+    float perspectiveCompensation = 0;
+    std::string puckImagePath;
+    std::string puckShadowImagePath;
+    std::string puckHatImagePath;
+};
+
+class RenderLocationIndicatorImpl {
+protected:
+    struct vec2 {
+        GLfloat x = 0.0f;
+        GLfloat y = 0.0f;
+
+        vec2(GLfloat x_, GLfloat y_) : x(x_), y(y_) {}
+        vec2() = default;
+        explicit vec2(const Point<double>& p) : x(p.x), y(p.y) {}
+        vec2(const vec2& o) = default;
+        vec2(vec2&& o) = default;
+        vec2& operator=(vec2&& o) = default;
+        vec2& operator=(const vec2& o) = default;
+        float length() const { return std::sqrt(x * x + y * y); }
+        vec2 normalized() const {
+            const float size = length();
+            return {x / size, y / size};
+        }
+        void normalize() { *this = normalized(); }
+        vec2 mirrored(const vec2& mirror) const {
+            float k = dot(mirror) / mirror.length();
+            return 2.0 * k * mirror - (*this);
+        }
+        float dot(const vec2& v2) const { return x * v2.x + y * v2.y; }
+        vec2 rotated(float degrees) const {
+            const float cs = std::cos(degrees * util::DEG2RAD);
+            const float sn = std::sin(degrees * util::DEG2RAD);
+            return vec2{x * cs + y * sn, x * sn + y * cs}.normalized();
+        }
+        float bearing() const {
+            const vec2 norm = normalized();
+
+            // From theta to bearing
+            return util::wrap<float>(M_PI_2 - std::atan2(-norm.y, norm.x), 0, M_PI * 2.0) * util::RAD2DEG;
+        }
+        Point<double> toPoint() const { return {x, y}; }
+
+        friend vec2 operator-(const vec2& v) { return {-v.x, -v.y}; }
+        friend vec2 operator*(double a, const vec2& v) { return {GLfloat(v.x * a), GLfloat(v.y * a)}; }
+        friend vec2 operator+(const vec2& v1, const vec2& v2) { return {v1.x + v2.x, v1.y + v2.y}; }
+        friend vec2 operator-(const vec2& v1, const vec2& v2) { return {v1.x - v2.x, v1.y - v2.y}; }
+    };
+
+    struct Shader {
+        virtual ~Shader() { release(); }
+        void release() {
+            if (!program) return;
+            MBGL_CHECK_ERROR(glDetachShader(program, vertexShader));
+            MBGL_CHECK_ERROR(glDetachShader(program, fragmentShader));
+            MBGL_CHECK_ERROR(glDeleteShader(vertexShader));
+            MBGL_CHECK_ERROR(glDeleteShader(fragmentShader));
+            MBGL_CHECK_ERROR(glDeleteProgram(program));
+            program = vertexShader = fragmentShader = 0;
+        }
+        void initialize(const GLchar* const& vsSource, const GLchar* const& fsSource) {
+            if (program) return;
+            program = MBGL_CHECK_ERROR(glCreateProgram());
+            vertexShader = MBGL_CHECK_ERROR(glCreateShader(GL_VERTEX_SHADER));
+            fragmentShader = MBGL_CHECK_ERROR(glCreateShader(GL_FRAGMENT_SHADER));
+            MBGL_CHECK_ERROR(glShaderSource(vertexShader, 1, &vsSource, nullptr));
+            MBGL_CHECK_ERROR(glCompileShader(vertexShader));
+            MBGL_CHECK_ERROR(glAttachShader(program, vertexShader));
+            MBGL_CHECK_ERROR(glShaderSource(fragmentShader, 1, &fsSource, nullptr));
+            MBGL_CHECK_ERROR(glCompileShader(fragmentShader));
+            MBGL_CHECK_ERROR(glAttachShader(program, fragmentShader));
+            MBGL_CHECK_ERROR(glLinkProgram(program));
+            pullLocations();
+        }
+        virtual void bind() { MBGL_CHECK_ERROR(glUseProgram(program)); }
+        void detach() { MBGL_CHECK_ERROR(glUseProgram(0)); }
+        virtual void pullLocations(){};
+
+        GLuint program = 0;
+        GLuint vertexShader = 0;
+        GLuint fragmentShader = 0;
+    };
+
+    struct SimpleShader : public Shader {
+        // Note that custom layers need to draw geometry with a z value of 1 to take advantage of
+        // depth-based fragment culling.
+        const GLchar* vertexShaderSource = R"MBGL_SHADER(
+#ifdef GL_ES
+precision highp float;
+#endif
+
+attribute vec2 a_pos;
+uniform mat4 u_matrix;
+void main() {
+    gl_Position = u_matrix * vec4(a_pos, 0, 1);
+}
+)MBGL_SHADER";
+
+        const GLchar* fragmentShaderSource = R"MBGL_SHADER(
+#ifdef GL_ES
+precision highp float;
+#endif
+
+uniform vec4 u_color;
+void main() {
+    gl_FragColor = u_color;
+}
+)MBGL_SHADER";
+
+        void initialize() { Shader::initialize(SimpleShader::vertexShaderSource, SimpleShader::fragmentShaderSource); }
+
+        void pullLocations() override {
+            a_pos = MBGL_CHECK_ERROR(glGetAttribLocation(program, "a_pos"));
+            u_color = MBGL_CHECK_ERROR(glGetUniformLocation(program, "u_color"));
+            u_matrix = MBGL_CHECK_ERROR(glGetUniformLocation(program, "u_matrix"));
+        }
+        void bind() override {
+            SimpleShader::initialize();
+            Shader::bind();
+        }
+
+        GLuint a_pos = 0;
+        GLuint u_color = 0;
+        GLuint u_matrix = 0;
+    };
+
+    struct TexturedShader : public Shader {
+        const GLchar* vertexShaderSource = R"MBGL_SHADER(
+#ifdef GL_ES
+precision highp float;
+#endif
+
+attribute vec2 a_pos;
+attribute vec2 a_texCoord;
+uniform mat4 u_matrix;
+varying vec2 v_texCoord;
+void main() {
+    gl_Position = u_matrix * vec4(a_pos, 0, 1);
+    v_texCoord = a_texCoord;
+}
+)MBGL_SHADER";
+
+        const GLchar* fragmentShaderSource = R"MBGL_SHADER(
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform sampler2D u_image;
+varying vec2 v_texCoord;
+void main() {
+    vec4 color = texture2D(u_image, v_texCoord);
+    gl_FragColor = color;
+}
+)MBGL_SHADER";
+
+        void initialize() { Shader::initialize(vertexShaderSource, fragmentShaderSource); }
+
+        void pullLocations() override {
+            a_pos = MBGL_CHECK_ERROR(glGetAttribLocation(program, "a_pos"));
+            a_texCoord = MBGL_CHECK_ERROR(glGetAttribLocation(program, "a_texCoord"));
+            u_image = MBGL_CHECK_ERROR(glGetUniformLocation(program, "u_image"));
+            u_matrix = MBGL_CHECK_ERROR(glGetUniformLocation(program, "u_matrix"));
+        }
+        void bind() override {
+            TexturedShader::initialize();
+            Shader::bind();
+        }
+
+        GLuint a_pos = 0;
+        GLuint a_texCoord = 0;
+        GLuint u_image = 0;
+        GLuint u_matrix = 0;
+    };
+
+    struct Buffer {
+        virtual ~Buffer() { release(); }
+        void release() {
+            if (!bufferId) return;
+            MBGL_CHECK_ERROR(glDeleteBuffers(1, &bufferId));
+            bufferId = 0;
+        }
+        void initialize() {
+            if (!bufferId) MBGL_CHECK_ERROR(glGenBuffers(1, &bufferId));
+        }
+        void bind(const GLenum target = GL_ARRAY_BUFFER) {
+            initialize();
+            MBGL_CHECK_ERROR(glBindBuffer(target, bufferId));
+        }
+        void detach(const GLenum target = GL_ARRAY_BUFFER) { MBGL_CHECK_ERROR(glBindBuffer(target, 0)); }
+        template <typename T, std::size_t N>
+        void upload(const std::array<T, N>& data) {
+            bind();
+            MBGL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, N * sizeof(T), data.data(), GL_STATIC_DRAW));
+            size = static_cast<unsigned int>(N * sizeof(T));
+            elements = N;
+        }
+        template <typename T>
+        void upload(const std::vector<T>& data) {
+            bind();
+            MBGL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, data.size() * sizeof(T), data.data(), GL_STATIC_DRAW));
+            size = data.size() * sizeof(T);
+            elements = data.size();
+        }
+
+        GLuint bufferId = 0;
+        unsigned int size = 0;
+        unsigned int elements = 0;
+    };
+
+public:
+    struct Texture {
+        ~Texture() { release(); }
+        void release() {
+            MBGL_CHECK_ERROR(glDeleteTextures(1, &texId));
+            texId = 0;
+            image = nullptr;
+        }
+        /*
+            Assign can be called any time. Conversely, upload must be called with a bound gl context.
+        */
+        void assign(const Immutable<style::Image::Impl>* img) {
+            if ((img && &img->get()->image == image) || (!img && !image)) return;
+            imageDirty = true;
+            image = (img) ? &img->get()->image : nullptr;
+            if (img)
+                sharedImage = *img; // keep reference until uploaded
+            else
+                sharedImage = nullopt;
+        }
+
+        void upload() {
+            if (!imageDirty) return;
+            imageDirty = false;
+            initialize();
+
+            MBGL_CHECK_ERROR(glBindTexture(GL_TEXTURE_2D, texId));
+            if (!image || !image->valid()) {
+                MBGL_CHECK_ERROR(glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr));
+            } else {
+                MBGL_CHECK_ERROR(glTexImage2D(GL_TEXTURE_2D,
+                                              0,
+                                              GL_RGBA,
+                                              image->size.width,
+                                              image->size.height,
+                                              0,
+                                              GL_RGBA,
+                                              GL_UNSIGNED_BYTE,
+                                              image->data.get()));
+                MBGL_CHECK_ERROR(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR));
+                MBGL_CHECK_ERROR(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR));
+                MBGL_CHECK_ERROR(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE));
+                MBGL_CHECK_ERROR(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE));
+                MBGL_CHECK_ERROR(glGenerateMipmap(GL_TEXTURE_2D));
+                if (RenderLocationIndicatorImpl::anisotropicFilteringAvailable)
+                    MBGL_CHECK_ERROR(glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 16));
+            }
+            detach();
+            sharedImage = nullopt;
+        }
+        void initialize() {
+            if (texId != 0) return;
+            MBGL_CHECK_ERROR(glGenTextures(1, &texId));
+        }
+        void bind(int textureUnit = -1) {
+            initialize();
+            if (!image && !imageDirty) return;
+
+            upload();
+            if (textureUnit >= 0) MBGL_CHECK_ERROR(glActiveTexture(GL_TEXTURE0 + textureUnit));
+            MBGL_CHECK_ERROR(glBindTexture(GL_TEXTURE_2D, texId));
+        }
+        void detach() { MBGL_CHECK_ERROR(glBindTexture(GL_TEXTURE_2D, 0)); }
+        bool isValid() { return imageDirty || image; }
+        GLuint texId = 0;
+        const mbgl::PremultipliedImage* image = nullptr;
+        optional<Immutable<style::Image::Impl>> sharedImage;
+        bool imageDirty = false;
+    };
+
+    RenderLocationIndicatorImpl() : ruler(0, mapbox::cheap_ruler::CheapRuler::Meters) {}
+
+    static bool hasExtension(const std::string& ext) {
+        if (const auto* extensions = reinterpret_cast<const char*>(MBGL_CHECK_ERROR(glGetString(GL_EXTENSIONS)))) {
+            if (strstr(extensions, ext.c_str()) != nullptr) return true;
+        }
+        return false;
+    }
+    void initialize() {
+        // Check if anisotropic filtering is available
+        if (initialized) return;
+        initialized = true;
+        if (hasExtension("GL_EXT_texture_filter_anisotropic")) anisotropicFilteringAvailable = true;
+        simpleShader.initialize();
+        texturedShader.initialize();
+        texCoords = {{{0.0f, 1.0f},
+                      {0.0f, 0.0f},
+                      {1.0f, 0.0f},
+                      {1.0f, 1.0f}}}; // Quads will be drawn as triangle fans. so bl, tl, tr, br
+        texCoordsBuffer.upload(texCoords);
+    }
+
+    void render(const mbgl::LocationIndicatorRenderParameters& params) {
+        initialize();
+        drawRadius(params);
+        drawShadow();
+        drawPuck();
+        drawHat();
+    }
+
+    void release() {
+        if (!simpleShader.program) return;
+        textures.clear();
+        buffer.release();
+        circleBuffer.release();
+        puckBuffer.release();
+        hatBuffer.release();
+        texCoordsBuffer.release();
+        simpleShader.release();
+        texturedShader.release();
+    }
+
+    void updatePuckGeometry(const mbgl::LocationIndicatorRenderParameters& params) {
+        if (params.projectionMatrix != oldParams.projectionMatrix) positionChanged = true;
+        if (params.puckPosition != oldParams.puckPosition) {
+            positionChanged = true;
+            ruler = mapbox::cheap_ruler::CheapRuler(params.puckPosition.latitude(),
+                                                    mapbox::cheap_ruler::CheapRuler::Meters);
+        } else if (params.puckBearing != oldParams.puckBearing ||
+                   params.puckLayersDisplacement != oldParams.puckLayersDisplacement ||
+                   params.perspectiveCompensation != oldParams.perspectiveCompensation ||
+                   params.puckSizePx != oldParams.puckSizePx || params.puckHatSizePx != oldParams.puckHatSizePx ||
+                   params.puckShadowSizePx != oldParams.puckShadowSizePx)
+            bearingChanged = true; // changes puck geometry but not necessarily the location
+        if (params.errorRadiusMeters != oldParams.errorRadiusMeters) radiusChanged = true;
+        if (params.puckImagePath != oldParams.puckImagePath)
+            setTextureFromImageID(params.puckImagePath, texPuck, params);
+        if (params.puckShadowImagePath != oldParams.puckShadowImagePath)
+            setTextureFromImageID(params.puckShadowImagePath, texShadow, params);
+        if (params.puckHatImagePath != oldParams.puckHatImagePath)
+            setTextureFromImageID(params.puckHatImagePath, texPuckHat, params);
+
+        projectionCircle = params.projectionMatrix;
+        const Point<double> positionMercator = project(params.puckPosition, *params.state);
+        mat4 translation;
+        matrix::identity(translation);
+        matrix::translate(translation, translation, positionMercator.x, positionMercator.y, 0.0);
+        matrix::multiply(projectionCircle, projectionCircle, translation);
+
+        if (positionChanged) {
+            updateRadius(params);
+            updatePuck(params);
+            positionChanged = false;
+        } else {
+            if (radiusChanged) {
+                updateRadius(params);
+            }
+            if (bearingChanged) {
+                updatePuck(params);
+            }
+        }
+        oldParams = params;
+    }
+
+protected:
+    static ScreenCoordinate latLngToScreenCoordinate(const LatLng& p, const TransformState& s) {
+        LatLng unwrappedLatLng = p.wrapped();
+        unwrappedLatLng.unwrapForShortestPath(s.getLatLng(LatLng::Wrapped));
+        ScreenCoordinate point = s.latLngToScreenCoordinate(unwrappedLatLng);
+        point.y = s.getSize().height - point.y;
+        return point;
+    }
+
+    static Point<double> project(const LatLng& c, const TransformState& s) {
+        LatLng unwrappedLatLng = c.wrapped();
+        unwrappedLatLng.unwrapForShortestPath(s.getLatLng(LatLng::Wrapped));
+        return Projection::project(unwrappedLatLng, s.getScale());
+    }
+
+    static Point<double> unproject(const LatLng& c, const TransformState& s) {
+        LatLng unwrappedLatLng = c.wrapped();
+        unwrappedLatLng.unwrapForShortestPath(s.getLatLng(LatLng::Wrapped));
+        return Projection::project(unwrappedLatLng, s.getScale());
+    }
+
+    void updateRadius(const mbgl::LocationIndicatorRenderParameters& params) {
+        const TransformState& s = *params.state;
+        const unsigned long numVtxCircumference = circle.size() - 1;
+        const float bearingStep = 360.0f / float(numVtxCircumference - 1); // first and last points are the same
+        const mapbox::cheap_ruler::point centerPoint(params.puckPosition.longitude(), params.puckPosition.latitude());
+        Point<double> center = project(params.puckPosition, s);
+        circle[0] = {0, 0};
+
+        double mapBearing = util::wrap(util::RAD2DEG * params.bearing, 0.0, util::DEGREES_MAX);
+        for (unsigned long i = 1; i <= numVtxCircumference; ++i) {
+            const float bearing_ = float(i - 1) * bearingStep - mapBearing;
+            Point<double> poc = ruler.destination(centerPoint, params.errorRadiusMeters, bearing_);
+            circle[i] = vec2(project(LatLng(poc.y, poc.x), s) - center);
+        }
+        radiusChanged = false;
+    }
+
+    // Size in "map pixels" for a screen pixel
+    static float pixelSizeToWorldSizeH(const LatLng& pos, const TransformState& s) {
+        ScreenCoordinate posScreen = latLngToScreenCoordinate(pos, s);
+        ScreenCoordinate posScreenLeftPx = posScreen;
+        posScreenLeftPx.x -= 1;
+        LatLng posLeftPx = screenCoordinateToLatLng(posScreenLeftPx, s);
+        Point<double> posMerc = project(pos, s);
+        Point<double> posLeftPxMerc = project(posLeftPx, s);
+        return vec2(posMerc - posLeftPxMerc).length();
+    }
+
+    static vec2 verticalDirectionMercator(const LatLng& pos, const TransformState& s) {
+        ScreenCoordinate posScreen = latLngToScreenCoordinate(pos, s);
+        Point<double> posMerc = project(pos, s);
+        return verticalDirectionMercator(posScreen, posMerc, s);
+    }
+
+    static vec2 verticalDirectionMercator(const ScreenCoordinate& pos, Point<double> posMerc, const TransformState& s) {
+        ScreenCoordinate screenDy = pos;
+        screenDy.y -= 1;
+        LatLng posDy = screenCoordinateToLatLng(screenDy, s);
+        Point<double> posMercDy = project(posDy, s);
+        return verticalDirectionMercator(posMerc, posMercDy);
+    }
+
+    static vec2 verticalDirectionMercator(const Point<double>& posMerc, const Point<double>& posMercDy) {
+        Point<double> verticalShiftMercator = posMercDy - posMerc;
+        vec2 res(verticalShiftMercator);
+        return res.normalized();
+    }
+
+    static Point<double> hatShadowShiftVector(const LatLng& position,
+                                              const mbgl::LocationIndicatorRenderParameters& params) {
+        const TransformState& s = *params.state;
+        ScreenCoordinate posScreen = latLngToScreenCoordinate(position, s);
+        posScreen.y = params.height - 1; // moving it to bottom
+        Point<double> posMerc = project(screenCoordinateToLatLng(posScreen, s), s);
+        vec2 verticalShiftAtPos = verticalDirectionMercator(posScreen, posMerc, s);
+        return {verticalShiftAtPos.x, verticalShiftAtPos.y};
+    }
+
+    static vec2 directionAtPositionScreen(const LatLng& position, float bearing, const TransformState& s) {
+        const double scale = s.getScale();
+        const vec2 rot = vec2(0.0, -1.0).rotated(-bearing);
+        Point<double> posMerc = project(position, s);
+        Point<double> posMercDelta = posMerc + rot.toPoint();
+        ScreenCoordinate posScreen = latLngToScreenCoordinate(position, s);
+        ScreenCoordinate posScreenDelta = latLngToScreenCoordinate(Projection::unproject(posMercDelta, scale), s);
+        return vec2(posScreenDelta - posScreen).normalized();
+    }
+
+    void updatePuck(const mbgl::LocationIndicatorRenderParameters& params) { return updatePuckPerspective(params); }
+
+    void updatePuckPerspective(const mbgl::LocationIndicatorRenderParameters& params) {
+        const TransformState& s = *params.state;
+        projectionPuck = projectionCircle; // Duplicated as it might change, depending on what puck style is chosen.
+        const mapbox::cheap_ruler::point centerPoint(params.puckPosition.longitude(), params.puckPosition.latitude());
+        static constexpr float bearings[]{
+            225.0f, 315.0f, 45.0f, 135.0f}; // Quads will be drawn as triangle fans. so bl, tl, tr, br
+#ifndef M_SQRT2
+        static constexpr const float M_SQRT2 = std::sqrt(2.0f);
+#endif
+        // The puck has to stay square at all zoom levels. CheapRuler::destination does not guarantee this at low zoom
+        // levels, so the extent has to be produced in mercator space
+        const double tilt = s.getPitch();
+
+        // Point<double> verticalShiftAtCenter { float(std::sin(util::DEG2RAD * util::wrap<float>(-t.getBearing() *
+        // util::RAD2DEG, 0.0f, 360.0f) )),
+        //                                      -float(std::cos(util::DEG2RAD * util::wrap<float>(-t.getBearing() *
+        //                                      util::RAD2DEG, 0.0f, 360.0f))) };
+        // would be correct only in the vertical center of the map. As soon as position goes away from that line,
+        // the shift direction is skewed by the perspective projection.
+        // So the way to have a shift aligned to the screen vertical axis is to find this direction in screen space, and
+        // convert it back to map space. This would yield an always straight up shift. However, going further (= the
+        // opposite direction of where the lines are converging in the projection) might produce an even more realistic
+        // effect. But in this case, it empirically seems that the largest shift that look acceptable is what is
+        // obtained at the bottom of the window, avoiding the wider converging lines that pass by the edge of the screen
+        // going toward the top.
+
+        Point<double> verticalShift = hatShadowShiftVector(params.puckPosition, params);
+        const float horizontalScaleFactor =
+            (1.0f - params.perspectiveCompensation) +
+            util::clamp(pixelSizeToWorldSizeH(params.puckPosition, s), 0.8f, 100.1f) *
+                params.perspectiveCompensation; // Compensation factor for the perspective deformation
+        //     ^ clamping this to 0.8 to avoid growing the puck too much close to the camera.
+        const double shadowRadius =
+            params.puckShadowSizePx * M_SQRT2 * 0.5 *
+            horizontalScaleFactor; // Technically it's not the radius, but the half diagonal of the quad.
+        const double puckRadius = params.puckSizePx * M_SQRT2 * 0.5 * horizontalScaleFactor;
+        const double hatRadius = params.puckHatSizePx * M_SQRT2 * 0.5 * horizontalScaleFactor;
+
+        for (unsigned long i = 0; i < 4; ++i) {
+            const auto b = util::wrap<float>(params.puckBearing + bearings[i], 0.0f, 360.0f);
+
+            const Point<double> cornerDirection{float(std::sin(util::DEG2RAD * b)),
+                                                -float(std::cos(util::DEG2RAD * b))};
+
+            Point<double> shadowOffset = cornerDirection * shadowRadius;
+            Point<double> puckOffset = cornerDirection * puckRadius;
+            Point<double> hatOffset = cornerDirection * hatRadius;
+
+            shadowGeometry[i] =
+                vec2(shadowOffset + (verticalShift * (tilt * -params.puckLayersDisplacement * horizontalScaleFactor)));
+            puckGeometry[i] = vec2(puckOffset);
+            hatGeometry[i] =
+                vec2(hatOffset + (verticalShift * (tilt * params.puckLayersDisplacement * horizontalScaleFactor)));
+        }
+
+        bearingChanged = false;
+    }
+
+    void drawRadius(const mbgl::LocationIndicatorRenderParameters& params) {
+        if (!(params.errorRadiusMeters > 0.0) ||
+            (params.errorRadiusColor.a == 0.0 && params.errorRadiusBorderColor.a == 0.0))
+            return;
+
+        simpleShader.bind();
+        mbgl::gl::bindUniform(simpleShader.u_color, params.errorRadiusColor);
+        mbgl::gl::bindUniform(simpleShader.u_matrix, projectionCircle);
+
+        circleBuffer.upload(circle);
+        MBGL_CHECK_ERROR(glEnableVertexAttribArray(simpleShader.a_pos));
+        MBGL_CHECK_ERROR(glVertexAttribPointer(simpleShader.a_pos, 2, GL_FLOAT, GL_FALSE, 0, nullptr));
+
+        MBGL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_FAN, 0, circle.size()));
+        if (params.errorRadiusBorderColor.a > 0.0f) {
+            mbgl::gl::bindUniform(simpleShader.u_color, params.errorRadiusBorderColor);
+            MBGL_CHECK_ERROR(glLineWidth(1.0f));
+            MBGL_CHECK_ERROR(glDrawArrays(GL_LINE_STRIP, 1, circle.size() - 1));
+        }
+        MBGL_CHECK_ERROR(glDisableVertexAttribArray(simpleShader.a_pos));
+        circleBuffer.detach();
+        simpleShader.detach();
+    }
+
+    void drawQuad(Buffer& buf, std::array<vec2, 4>& data, std::shared_ptr<Texture>& texture) {
+        if (!texture || !texture->isValid()) return;
+        texturedShader.bind();
+        texture->bind(0);
+        glUniform1i(texturedShader.u_image, 0);
+        mbgl::gl::bindUniform(texturedShader.u_matrix, projectionPuck);
+
+        buf.bind();
+        buf.upload(data);
+        MBGL_CHECK_ERROR(glEnableVertexAttribArray(texturedShader.a_pos));
+        MBGL_CHECK_ERROR(glVertexAttribPointer(texturedShader.a_pos, 2, GL_FLOAT, GL_FALSE, 0, nullptr));
+
+        texCoordsBuffer.bind();
+        MBGL_CHECK_ERROR(glEnableVertexAttribArray(texturedShader.a_texCoord));
+        MBGL_CHECK_ERROR(glVertexAttribPointer(texturedShader.a_texCoord, 2, GL_FLOAT, GL_FALSE, 0, nullptr));
+
+        MBGL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_FAN, 0, 4));
+        texture->detach();
+        texCoordsBuffer.detach();
+        texturedShader.detach();
+    }
+
+    void drawShadow() { drawQuad(shadowBuffer, shadowGeometry, texShadow); }
+
+    void drawPuck() { drawQuad(puckBuffer, puckGeometry, texPuck); }
+
+    void drawHat() { drawQuad(hatBuffer, hatGeometry, texPuckHat); }
+
+    static LatLng screenCoordinateToLatLng(const ScreenCoordinate& p,
+                                           const TransformState& s,
+                                           LatLng::WrapMode wrapMode = LatLng::Wrapped) {
+        ScreenCoordinate flippedPoint = p;
+        flippedPoint.y = s.getSize().height - flippedPoint.y;
+        return s.screenCoordinateToLatLng(flippedPoint, wrapMode);
+    }
+
+    void setTextureFromImageID(const std::string& imagePath,
+                               std::shared_ptr<Texture>& tex,
+                               const mbgl::LocationIndicatorRenderParameters& params) {
+        if (textures.find(imagePath) == textures.end()) {
+            std::shared_ptr<Texture> tx = std::make_shared<Texture>();
+            if (!imagePath.empty() && params.imageManager)
+                tx->assign(params.imageManager->getSharedImage(imagePath));
+            else
+                tx->assign(nullptr);
+            textures[imagePath] = tx;
+        }
+        tex = textures.at(imagePath);
+    }
+
+    std::map<std::string, std::shared_ptr<Texture>> textures;
+    mapbox::cheap_ruler::CheapRuler ruler;
+    SimpleShader simpleShader;
+    TexturedShader texturedShader;
+    Buffer buffer;
+    Buffer circleBuffer;
+    Buffer shadowBuffer;
+    Buffer puckBuffer;
+    Buffer hatBuffer;
+    Buffer texCoordsBuffer;
+    std::shared_ptr<Texture> texShadow;
+    std::shared_ptr<Texture> texPuck;
+    std::shared_ptr<Texture> texPuckHat;
+
+    std::array<vec2, 73> circle; // 72 points + position
+    std::array<vec2, 4> shadowGeometry;
+    std::array<vec2, 4> puckGeometry;
+    std::array<vec2, 4> hatGeometry;
+    std::array<vec2, 4> texCoords;
+    mbgl::mat4 projectionCircle;
+    mbgl::mat4 projectionPuck;
+
+    bool positionChanged = false;
+    bool radiusChanged = false;
+    bool bearingChanged = false;
+    mbgl::LocationIndicatorRenderParameters oldParams;
+    bool initialized = false;
+
+public:
+    mbgl::LocationIndicatorRenderParameters parameters;
+    static bool anisotropicFilteringAvailable;
+};
+
+bool RenderLocationIndicatorImpl::anisotropicFilteringAvailable = false;
+
+using namespace style;
+namespace {
+
+inline const LocationIndicatorLayer::Impl& impl(const Immutable<style::Layer::Impl>& impl) {
+    assert(impl->getTypeInfo() == LocationIndicatorLayer::Impl::staticTypeInfo());
+    return static_cast<const LocationIndicatorLayer::Impl&>(*impl);
+}
+} // namespace
+
+RenderLocationIndicatorLayer::RenderLocationIndicatorLayer(Immutable<style::LocationIndicatorLayer::Impl> _impl)
+    : RenderLayer(makeMutable<LocationIndicatorLayerProperties>(std::move(_impl))),
+      renderImpl(new RenderLocationIndicatorImpl()),
+      unevaluated(impl(baseImpl).paint.untransitioned()) {
+    assert(gfx::BackendScope::exists());
+}
+
+RenderLocationIndicatorLayer::~RenderLocationIndicatorLayer() {
+    assert(gfx::BackendScope::exists());
+    if (!contextDestroyed) MBGL_CHECK_ERROR(renderImpl->release());
+}
+
+void RenderLocationIndicatorLayer::transition(const TransitionParameters& parameters) {
+    unevaluated = impl(baseImpl).paint.transitioned(parameters, std::move(unevaluated));
+}
+
+void RenderLocationIndicatorLayer::evaluate(const PropertyEvaluationParameters& parameters) {
+    passes = RenderPass::Translucent;
+    auto properties = makeMutable<LocationIndicatorLayerProperties>(
+        staticImmutableCast<LocationIndicatorLayer::Impl>(baseImpl), unevaluated.evaluate(parameters));
+    const auto& evaluated = properties->evaluated;
+    auto& layout = impl(baseImpl).layout;
+
+    properties->renderPasses = mbgl::underlying_type(passes);
+
+    // paint
+    renderImpl->parameters.errorRadiusColor = evaluated.get<style::AccuracyRadiusColor>();
+    renderImpl->parameters.errorRadiusBorderColor = evaluated.get<style::AccuracyRadiusBorderColor>();
+    renderImpl->parameters.errorRadiusMeters = evaluated.get<style::AccuracyRadius>();
+    renderImpl->parameters.puckSizePx = evaluated.get<style::BearingImageSize>();
+    renderImpl->parameters.puckHatSizePx = evaluated.get<style::TopImageSize>();
+    renderImpl->parameters.puckShadowSizePx = evaluated.get<style::ShadowImageSize>();
+
+    const std::array<double, 3> pos = evaluated.get<style::Location>();
+    renderImpl->parameters.puckPosition = LatLng{pos[0], pos[1]};
+
+    // layout
+    if (!layout.get<style::Bearing>().isUndefined())
+        renderImpl->parameters.puckBearing = layout.get<style::Bearing>().asConstant();
+    if (!layout.get<style::BearingImage>().isUndefined())
+        renderImpl->parameters.puckImagePath = layout.get<style::BearingImage>().asConstant().id();
+    if (!layout.get<style::ShadowImage>().isUndefined())
+        renderImpl->parameters.puckShadowImagePath = layout.get<style::ShadowImage>().asConstant().id();
+    if (!layout.get<style::TopImage>().isUndefined())
+        renderImpl->parameters.puckHatImagePath = layout.get<style::TopImage>().asConstant().id();
+    if (!layout.get<style::ImageTiltDisplacement>().isUndefined())
+        renderImpl->parameters.puckLayersDisplacement = layout.get<style::ImageTiltDisplacement>().asConstant();
+    if (!layout.get<style::PerspectiveCompensation>().isUndefined())
+        renderImpl->parameters.perspectiveCompensation = layout.get<style::PerspectiveCompensation>().asConstant();
+
+    evaluatedProperties = std::move(properties);
+}
+
+bool RenderLocationIndicatorLayer::hasTransition() const {
+    return unevaluated.hasTransition();
+}
+bool RenderLocationIndicatorLayer::hasCrossfade() const {
+    return false;
+}
+
+void RenderLocationIndicatorLayer::markContextDestroyed() {
+    contextDestroyed = true;
+}
+
+void RenderLocationIndicatorLayer::prepare(const LayerPrepareParameters& p) {
+    renderImpl->parameters.imageManager = &p.imageManager;
+    const TransformState& state = p.state;
+    renderImpl->parameters.state = &state;
+
+    renderImpl->parameters.width = state.getSize().width;
+    renderImpl->parameters.height = state.getSize().height;
+    renderImpl->parameters.latitude = state.getLatLng().latitude();
+    renderImpl->parameters.longitude = state.getLatLng().longitude();
+    renderImpl->parameters.zoom = state.getZoom();
+    renderImpl->parameters.bearing = -state.getBearing() * util::RAD2DEG;
+    renderImpl->parameters.pitch = state.getPitch();
+    mat4 projMatrix;
+    state.getProjMatrix(projMatrix);
+    renderImpl->parameters.projectionMatrix = projMatrix;
+
+    renderImpl->updatePuckGeometry(renderImpl->parameters);
+}
+
+void RenderLocationIndicatorLayer::render(PaintParameters& paintParameters) {
+    auto& glContext = static_cast<gl::Context&>(paintParameters.context);
+
+    // Reset GL state to a known state so the CustomLayer always has a clean slate.
+    glContext.bindVertexArray = 0;
+    glContext.setDepthMode(paintParameters.depthModeForSublayer(0, gfx::DepthMaskType::ReadOnly));
+    glContext.setStencilMode(gfx::StencilMode::disabled());
+    glContext.setColorMode(paintParameters.colorModeForRenderPass()); // this is gfx::ColorMode::alphaBlended()
+    glContext.setCullFaceMode(gfx::CullFaceMode::disabled());
+
+    MBGL_CHECK_ERROR(renderImpl->render(renderImpl->parameters));
+
+    // Reset the view back to our original one, just in case the CustomLayer changed
+    // the viewport or Framebuffer.
+    paintParameters.backend.getDefaultRenderable().getResource<gl::RenderableResource>().bind();
+    glContext.setDirtyState();
+}
+
+} // namespace mbgl