6 files changed, 266 insertions, 0 deletions
diff --git a/src/mbgl/gl/custom_layer.cpp b/src/mbgl/gl/custom_layer.cpp
new file mode 100644
index 0000000000..456467e904
--- /dev/null
+++ b/src/mbgl/gl/custom_layer.cpp
@@ -0,0 +1,59 @@
+#include <mbgl/gl/custom_layer.hpp>
+#include <mbgl/gl/custom_layer_impl.hpp>
+#include <mbgl/gl/render_custom_layer.hpp>
+#include <mbgl/style/layer_observer.hpp>
+
+namespace mbgl {
+namespace style {
+
+namespace {
+const LayerTypeInfo typeInfoCustom{"",
+                                   LayerTypeInfo::Source::NotRequired,
+                                   LayerTypeInfo::Pass3D::NotRequired,
+                                   LayerTypeInfo::Layout::NotRequired,
+                                   LayerTypeInfo::FadingTiles::NotRequired,
+                                   LayerTypeInfo::CrossTileIndex::NotRequired,
+                                   LayerTypeInfo::TileKind::NotRequired};
+}  // namespace
+
+CustomLayer::CustomLayer(const std::string& layerID,
+                         std::unique_ptr<CustomLayerHost> host)
+    : Layer(makeMutable<Impl>(layerID, std::move(host))) {
+}
+
+CustomLayer::~CustomLayer() = default;
+
+const CustomLayer::Impl& CustomLayer::impl() const {
+    return static_cast<const Impl&>(*baseImpl);
+}
+
+Mutable<CustomLayer::Impl> CustomLayer::mutableImpl() const {
+    return makeMutable<Impl>(impl());
+}
+
+std::unique_ptr<Layer> CustomLayer::cloneRef(const std::string&) const {
+    assert(false);
+    return nullptr;
+}
+
+using namespace conversion;
+
+optional<Error> CustomLayer::setProperty(const std::string&, const Convertible&) {
+    return Error { "layer doesn't support this property" };
+}
+
+StyleProperty CustomLayer::getProperty(const std::string&) const {
+    return {};
+}
+
+Mutable<Layer::Impl> CustomLayer::mutableBaseImpl() const {
+    return staticMutableCast<Layer::Impl>(mutableImpl());
+}
+
+// static
+const LayerTypeInfo* CustomLayer::Impl::staticTypeInfo() noexcept {
+    return &typeInfoCustom;
+}
+
+} // namespace style
+} // namespace mbgl
diff --git a/src/mbgl/gl/custom_layer_factory.cpp b/src/mbgl/gl/custom_layer_factory.cpp
new file mode 100644
index 0000000000..616d0271e0
--- /dev/null
+++ b/src/mbgl/gl/custom_layer_factory.cpp
@@ -0,0 +1,21 @@
+#include <mbgl/gl/custom_layer.hpp>
+#include <mbgl/gl/custom_layer_factory.hpp>
+#include <mbgl/gl/custom_layer_impl.hpp>
+#include <mbgl/gl/render_custom_layer.hpp>
+
+namespace mbgl {
+
+const style::LayerTypeInfo* CustomLayerFactory::getTypeInfo() const noexcept {
+    return style::CustomLayer::Impl::staticTypeInfo();
+}
+
+std::unique_ptr<style::Layer> CustomLayerFactory::createLayer(const std::string&, const style::conversion::Convertible&) noexcept {
+    assert(false);
+    return nullptr;
+}
+
+std::unique_ptr<RenderLayer> CustomLayerFactory::createRenderLayer(Immutable<style::Layer::Impl> impl) noexcept {
+    return std::make_unique<RenderCustomLayer>(staticImmutableCast<style::CustomLayer::Impl>(impl));
+}
+
+} // namespace mbgl
diff --git a/src/mbgl/gl/custom_layer_impl.cpp b/src/mbgl/gl/custom_layer_impl.cpp
new file mode 100644
index 0000000000..85df44bc80
--- /dev/null
+++ b/src/mbgl/gl/custom_layer_impl.cpp
@@ -0,0 +1,20 @@
+#include <mbgl/gl/custom_layer_impl.hpp>
+
+namespace mbgl {
+namespace style {
+
+CustomLayer::Impl::Impl(const std::string& id_,
+                        std::unique_ptr<CustomLayerHost> host_)
+    : Layer::Impl(id_, std::string()) {
+    host = std::move(host_);
+}
+
+bool CustomLayer::Impl::hasLayoutDifference(const Layer::Impl&) const {
+    return false;
+}
+
+void CustomLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const {
+}
+
+} // namespace style
+} // namespace mbgl
diff --git a/src/mbgl/gl/custom_layer_impl.hpp b/src/mbgl/gl/custom_layer_impl.hpp
new file mode 100644
index 0000000000..0c9339adf1
--- /dev/null
+++ b/src/mbgl/gl/custom_layer_impl.hpp
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <mbgl/gl/custom_layer.hpp>
+#include <mbgl/style/layer_impl.hpp>
+#include <mbgl/style/layer_properties.hpp>
+
+#include <memory>
+
+namespace mbgl {
+
+class TransformState;
+
+namespace style {
+
+class CustomLayer::Impl : public Layer::Impl {
+public:
+    Impl(const std::string& id,
+         std::unique_ptr<CustomLayerHost> host);
+
+    bool hasLayoutDifference(const Layer::Impl&) const override;
+    void stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const override;
+
+    std::shared_ptr<CustomLayerHost> host;
+
+    DECLARE_LAYER_TYPE_INFO;
+};
+
+class CustomLayerProperties final : public LayerProperties {
+public:
+    explicit CustomLayerProperties(Immutable<CustomLayer::Impl> impl)
+        : LayerProperties(std::move(impl)) {}
+};
+
+} // namespace style
+} // namespace mbgl
diff --git a/src/mbgl/gl/render_custom_layer.cpp b/src/mbgl/gl/render_custom_layer.cpp
new file mode 100644
index 0000000000..bb12ec1fcf
--- /dev/null
+++ b/src/mbgl/gl/render_custom_layer.cpp
@@ -0,0 +1,104 @@
+#include <mbgl/gfx/backend_scope.hpp>
+#include <mbgl/gfx/renderer_backend.hpp>
+#include <mbgl/gl/context.hpp>
+#include <mbgl/gl/custom_layer_impl.hpp>
+#include <mbgl/gl/render_custom_layer.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/paint_parameters.hpp>
+#include <mbgl/util/mat4.hpp>
+
+namespace mbgl {
+
+using namespace style;
+
+namespace {
+
+inline const CustomLayer::Impl& impl(const Immutable<style::Layer::Impl>& impl) {
+    assert(impl->getTypeInfo() == CustomLayer::Impl::staticTypeInfo());
+    return static_cast<const CustomLayer::Impl&>(*impl);
+}
+
+} // namespace
+
+RenderCustomLayer::RenderCustomLayer(Immutable<style::CustomLayer::Impl> _impl)
+    : RenderLayer(makeMutable<CustomLayerProperties>(std::move(_impl))),
+      host(impl(baseImpl).host) {
+    assert(gfx::BackendScope::exists());
+    MBGL_CHECK_ERROR(host->initialize());
+}
+
+RenderCustomLayer::~RenderCustomLayer() {
+    assert(gfx::BackendScope::exists());
+    if (contextDestroyed) {
+        host->contextLost();
+    } else {
+        MBGL_CHECK_ERROR(host->deinitialize());
+    }
+}
+
+void RenderCustomLayer::evaluate(const PropertyEvaluationParameters&) {
+    passes = RenderPass::Translucent;
+    // It is fine to not update `evaluatedProperties`, as `baseImpl` should never be updated for this layer.
+}
+
+bool RenderCustomLayer::hasTransition() const {
+    return false;
+}
+bool RenderCustomLayer::hasCrossfade() const {
+    return false;
+}
+
+void RenderCustomLayer::markContextDestroyed() {
+    contextDestroyed = true;
+}
+
+void RenderCustomLayer::prepare(const LayerPrepareParameters&) {
+}
+
+void RenderCustomLayer::render(PaintParameters& paintParameters) {
+    if (host != impl(baseImpl).host) {
+        //If the context changed, deinitialize the previous one before initializing the new one.
+        if (host && !contextDestroyed) {
+            MBGL_CHECK_ERROR(host->deinitialize());
+        }
+        host = impl(baseImpl).host;
+        MBGL_CHECK_ERROR(host->initialize());
+    }
+
+    // TODO: remove cast
+    auto& glContext = static_cast<gl::Context&>(paintParameters.context);
+    const TransformState& state = paintParameters.state;
+
+    // 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());
+    glContext.setCullFaceMode(gfx::CullFaceMode::disabled());
+
+    CustomLayerRenderParameters parameters;
+
+    parameters.width = state.getSize().width;
+    parameters.height = state.getSize().height;
+    parameters.latitude = state.getLatLng().latitude();
+    parameters.longitude = state.getLatLng().longitude();
+    parameters.zoom = state.getZoom();
+    parameters.bearing = -state.getBearing() * util::RAD2DEG;
+    parameters.pitch = state.getPitch();
+    parameters.fieldOfView = state.getFieldOfView();
+    mat4 projMatrix;
+    state.getProjMatrix(projMatrix);
+    parameters.projectionMatrix = projMatrix;
+
+    MBGL_CHECK_ERROR(host->render(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
diff --git a/src/mbgl/gl/render_custom_layer.hpp b/src/mbgl/gl/render_custom_layer.hpp
new file mode 100644
index 0000000000..2f5ae28209
--- /dev/null
+++ b/src/mbgl/gl/render_custom_layer.hpp
@@ -0,0 +1,27 @@
+#pragma once
+
+#include <mbgl/gl/custom_layer_impl.hpp>
+#include <mbgl/renderer/render_layer.hpp>
+
+namespace mbgl {
+
+class RenderCustomLayer final : public RenderLayer {
+public:
+    explicit RenderCustomLayer(Immutable<style::CustomLayer::Impl>);
+    ~RenderCustomLayer() override;
+
+private:
+    void transition(const TransitionParameters&) override {}
+    void evaluate(const PropertyEvaluationParameters&) override;
+    bool hasTransition() const override;
+    bool hasCrossfade() const override;
+    void markContextDestroyed() override;
+    void prepare(const LayerPrepareParameters&) override;
+
+    void render(PaintParameters&) override;
+
+    bool contextDestroyed = false;
+    std::shared_ptr<style::CustomLayerHost> host;
+};
+
+} // namespace mbgl