[core] Runtime style layer API

1 files changed, 78 insertions, 0 deletions

diff --git a/include/mbgl/style/layer.hpp b/include/mbgl/style/layer.hpp
new file mode 100644
index 0000000000..e6c33a9784
--- /dev/null
+++ b/include/mbgl/style/layer.hpp
@@ -0,0 +1,78 @@
+#ifndef MBGL_LAYER
+#define MBGL_LAYER
+
+#include <mbgl/util/noncopyable.hpp>
+#include <mbgl/style/types.hpp>
+
+#include <memory>
+
+namespace mbgl {
+
+/**
+ * The runtime representation of a [layer](https://www.mapbox.com/mapbox-gl-style-spec/#layers) from the Mapbox Style
+ * Specification.
+ *
+ * `Layer` is an abstract base class; concrete derived classes are provided for each layer type. `Layer` contains
+ * functionality that is common to all layer types:
+ *
+ * * Runtime type information: type predicates and casting
+ * * Accessors for properties common to all layer types: ID, visibility, etc.
+ * * Cloning and copying
+ *
+ * All other functionality lives in the derived classes. To instantiate a layer, create an instance of the desired
+ * type, passing the ID:
+ *
+ *     auto circleLayer = std::make_unique<CircleLayer>("my-circle-layer");
+ */
+class Layer : public mbgl::util::noncopyable {
+public:
+    virtual ~Layer();
+
+    // Check whether this layer is of the given subtype.
+    template <class T>
+    bool is() const;
+
+    // Dynamically cast this layer to the given subtype.
+    template <class T>
+    T* as() {
+        return is<T>() ? reinterpret_cast<T*>(this) : nullptr;
+    }
+
+    template <class T>
+    const T* as() const {
+        return is<T>() ? reinterpret_cast<const T*>(this) : nullptr;
+    }
+
+    const std::string& getID() const;
+
+    // Visibility
+    VisibilityType getVisibility() const;
+    void setVisibility(VisibilityType);
+
+    // Create a new layer with the specified `id` and `ref`. All other properties
+    // are copied from this layer.
+    std::unique_ptr<Layer> copy(const std::string& id,
+                                const std::string& ref) const;
+
+    // Private implementation
+    class Impl;
+    const std::unique_ptr<Impl> baseImpl;
+
+protected:
+    enum class Type {
+        Fill,
+        Line,
+        Circle,
+        Symbol,
+        Raster,
+        Background,
+        Custom,
+    };
+
+    const Type type;
+    Layer(Type, std::unique_ptr<Impl>);
+};
+
+} // namespace mbgl
+
+#endif