[core] layermanager folder

Move `LayerManager` and `LayerFactory` abstract classes to a dedicated folder.

2 files changed, 85 insertions, 0 deletions

diff --git a/include/mbgl/layermanager/layer_factory.hpp b/include/mbgl/layermanager/layer_factory.hpp
new file mode 100644
index 0000000000..3e2b2c3ddd
--- /dev/null
+++ b/include/mbgl/layermanager/layer_factory.hpp
@@ -0,0 +1,29 @@
+#pragma once
+
+#include <mbgl/style/layer.hpp>
+
+namespace mbgl {
+
+class RenderLayer;
+
+/**
+ * @brief The LayerFactory abstract class
+ * 
+ * This class is responsible for creation of the layer objects that belong to a concrete layer type.
+ */
+class LayerFactory {
+public:
+    virtual ~LayerFactory() = default;
+    /// Returns the layer type data.
+    virtual const style::LayerTypeInfo* getTypeInfo() const noexcept = 0;
+    /// Returns a new Layer instance on success call; returns `nulltptr` otherwise. 
+    virtual std::unique_ptr<style::Layer> createLayer(const std::string& id, const style::conversion::Convertible& value) noexcept = 0;
+    /// Returns a new RenderLayer instance on success call; returns `nulltptr` otherwise.
+    virtual std::unique_ptr<RenderLayer> createRenderLayer(Immutable<style::Layer::Impl>) noexcept = 0;
+
+protected:
+    optional<std::string> getSource(const style::conversion::Convertible& value) const noexcept;
+    bool initSourceLayerAndFilter(style::Layer*, const style::conversion::Convertible& value) const noexcept;
+};
+
+} // namespace mbgl
diff --git a/include/mbgl/layermanager/layer_manager.hpp b/include/mbgl/layermanager/layer_manager.hpp
new file mode 100644
index 0000000000..038a6dcb04
--- /dev/null
+++ b/include/mbgl/layermanager/layer_manager.hpp
@@ -0,0 +1,56 @@
+#pragma once
+
+#include <mbgl/style/layer.hpp>
+
+namespace mbgl {
+
+class LayerFactory;
+class RenderLayer;
+
+/**
+ * @brief A singleton class responsible for creating layer instances.
+ * 
+ * The LayerManager has implementation per platform. The LayerManager implementation
+ * defines what layer types are available and it can also disable annotations.
+ * 
+ * Linker excludes the unreachable code for the disabled annotations and layers
+ * from the binaries, significantly reducing their size.
+ */
+class LayerManager {
+public:
+    /**
+     * @brief A singleton getter.
+     * 
+     * @return LayerManager* 
+     */
+    static LayerManager* get() noexcept;
+
+    /// Returns a new Layer instance on success call; returns `nulltptr` otherwise.
+    std::unique_ptr<style::Layer> createLayer(const std::string& type, const std::string& id,
+                                              const style::conversion::Convertible& value, style::conversion::Error& error) noexcept;
+    /// Returns a new RenderLayer instance on success call; returns `nulltptr` otherwise.
+    std::unique_ptr<RenderLayer> createRenderLayer(Immutable<style::Layer::Impl>) noexcept;
+
+    /**
+     * @brief a build-time flag to enable/disable annotations in mapbox-gl-native core.
+     * 
+     * At the moment, the annotations implementation in core is creating concrete
+     * layer instances apart from LayerManager/LayerFactory code path.
+     * 
+     * So, annotations must be disabled if the LayerManager implementation does
+     * not provide line, fill or symbol layers (those, used by the annotations 
+     * implementation).
+     * 
+     * Note: in future, annotations implemantation will be moved from the core to platform 
+     * SDK (see https://github.com/mapbox/mapbox-plugins-android/tree/master/plugin-annotation)
+     * and this flag won't be needed any more.
+     */
+    static const bool annotationsEnabled;
+
+protected:
+    virtual ~LayerManager() = default;
+    virtual LayerFactory* getFactory(const std::string& type) noexcept = 0;
+    virtual LayerFactory* getFactory(const style::LayerTypeInfo*) noexcept = 0;
+};
+
+} // namespace mbgl