Consolidate `style::Layer` properties API

The `style::Layer` class now exposes all the properties contained at `style::LayerImpl`.
This allowed to drop `style::Layer::accept()` method usage, avoid the repeated generated code
and thus save some binary size.

This patch is a part of the layers modularization effort.

13 files changed, 61 insertions, 196 deletions

diff --git a/include/mbgl/style/layer.hpp b/include/mbgl/style/layer.hpp
index 3b7969ea79..dd8f1a1e0e 100644
--- a/include/mbgl/style/layer.hpp
+++ b/include/mbgl/style/layer.hpp
@@ -1,6 +1,5 @@
 #pragma once
 
-#include <mbgl/util/noncopyable.hpp>
 #include <mbgl/util/peer.hpp>
 #include <mbgl/util/immutable.hpp>
 #include <mbgl/util/optional.hpp>
@@ -27,6 +26,7 @@ class CustomLayer;
 class FillExtrusionLayer;
 class HeatmapLayer;
 class LayerObserver;
+class Filter;
 
 /**
  * The runtime representation of a [layer](https://www.mapbox.com/mapbox-gl-style-spec/#layers) from the Mapbox Style
@@ -44,8 +44,11 @@ class LayerObserver;
  *
  *     auto circleLayer = std::make_unique<CircleLayer>("my-circle-layer");
  */
-class Layer : public mbgl::util::noncopyable {
+class Layer {
 public:
+    Layer(const Layer& ) = delete;
+    Layer& operator=(const Layer&) = delete;
+
     virtual ~Layer();
 
     // Check whether this layer is of the given subtype.
@@ -63,60 +66,26 @@ public:
         return is<T>() ? reinterpret_cast<const T*>(this) : nullptr;
     }
 
-    // Convenience method for dynamic dispatch on the concrete layer type. Using
-    // method overloading, this allows consolidation of logic common to vector-based
-    // layers (Fill, FillExtrusion, Line, Circle, or Symbol). For example:
-    //
-    //     struct Visitor {
-    //         void operator()(CustomLayer&) { ... }
-    //         void operator()(RasterLayer&) { ... }
-    //         void operator()(BackgroundLayer&) { ... }
-    //         template <class VectorLayer>
-    //         void operator()(VectorLayer&) { ... }
-    //     };
-    //
-    template <class V>
-    auto accept(V&& visitor) {
-        switch (getType()) {
-        case LayerType::Fill:
-            return std::forward<V>(visitor)(*as<FillLayer>());
-        case LayerType::Line:
-            return std::forward<V>(visitor)(*as<LineLayer>());
-        case LayerType::Circle:
-            return std::forward<V>(visitor)(*as<CircleLayer>());
-        case LayerType::Symbol:
-            return std::forward<V>(visitor)(*as<SymbolLayer>());
-        case LayerType::Raster:
-            return std::forward<V>(visitor)(*as<RasterLayer>());
-        case LayerType::Background:
-            return std::forward<V>(visitor)(*as<BackgroundLayer>());
-        case LayerType::Hillshade:
-            return std::forward<V>(visitor)(*as<HillshadeLayer>());
-        case LayerType::Custom:
-            return std::forward<V>(visitor)(*as<CustomLayer>());
-        case LayerType::FillExtrusion:
-            return std::forward<V>(visitor)(*as<FillExtrusionLayer>());
-        case LayerType::Heatmap:
-            return std::forward<V>(visitor)(*as<HeatmapLayer>());
-        }
-
-        // Not reachable, but placate GCC.
-        assert(false);
-        throw new std::runtime_error("unknown layer type");
-    }
-
     LayerType getType() const;
     std::string getID() const;
+    // Source
+    std::string getSourceID() const;
+    std::string getSourceLayer() const;
+    void setSourceLayer(const std::string& sourceLayer);
+
+    // Filter
+    const Filter& getFilter() const;
+    void setFilter(const Filter&);
 
     // Visibility
     VisibilityType getVisibility() const;
-    virtual void setVisibility(VisibilityType) = 0;
+    void setVisibility(VisibilityType);
 
     // Zoom range
     float getMinZoom() const;
     float getMaxZoom() const;
-    virtual void setMinZoom(float) = 0;
-    virtual void setMaxZoom(float) = 0;
+    void setMinZoom(float);
+    void setMaxZoom(float);
 
     // Dynamic properties
     virtual optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) = 0;
@@ -124,21 +93,25 @@ public:
     optional<conversion::Error> setVisibility(const conversion::Convertible& value);
 
     // Private implementation
+    // TODO : We should not have public mutable data members.
     class Impl;
     Immutable<Impl> baseImpl;
 
-    Layer(Immutable<Impl>);
-
     // Create a layer, copying all properties except id and paint properties from this layer.
     virtual std::unique_ptr<Layer> cloneRef(const std::string& id) const = 0;
 
-    LayerObserver* observer = nullptr;
+    
     void setObserver(LayerObserver*);
 
     // For use in SDK bindings, which store a reference to a platform-native peer
     // object here, so that separately-obtained references to this object share
     // identical platform-native peers.
     util::peer peer;
+protected:
+    Layer(Immutable<Impl>);   
+    virtual Mutable<Impl> mutableBaseImpl() const = 0;
+
+    LayerObserver* observer = nullptr;
 };
 
 } // namespace style
diff --git a/include/mbgl/style/layers/background_layer.hpp b/include/mbgl/style/layers/background_layer.hpp
index ef01ea41be..7d7753cbff 100644
--- a/include/mbgl/style/layers/background_layer.hpp
+++ b/include/mbgl/style/layers/background_layer.hpp
@@ -19,13 +19,6 @@ public:
     BackgroundLayer(const std::string& layerID);
     ~BackgroundLayer() final;
 
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -58,6 +51,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     BackgroundLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/circle_layer.hpp b/include/mbgl/style/layers/circle_layer.hpp
index 0f8d1c0c13..909412dbab 100644
--- a/include/mbgl/style/layers/circle_layer.hpp
+++ b/include/mbgl/style/layers/circle_layer.hpp
@@ -19,21 +19,6 @@ public:
     CircleLayer(const std::string& layerID, const std::string& sourceID);
     ~CircleLayer() final;
 
-    // Source
-    const std::string& getSourceID() const;
-    const std::string& getSourceLayer() const;
-    void setSourceLayer(const std::string& sourceLayer);
-
-    void setFilter(const Filter&);
-    const Filter& getFilter() const;
-
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -114,6 +99,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     CircleLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/custom_layer.hpp b/include/mbgl/style/layers/custom_layer.hpp
index 4b4c770489..4ae59dfae3 100644
--- a/include/mbgl/style/layers/custom_layer.hpp
+++ b/include/mbgl/style/layers/custom_layer.hpp
@@ -68,13 +68,6 @@ public:
 
     ~CustomLayer() final;
 
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -88,10 +81,9 @@ public:
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
 
     CustomLayer(const CustomLayer&) = delete;
-};
 
-template <>
-bool Layer::is<CustomLayer>() const;
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
+};
 
 } // namespace style
 } // namespace mbgl
diff --git a/include/mbgl/style/layers/fill_extrusion_layer.hpp b/include/mbgl/style/layers/fill_extrusion_layer.hpp
index d30ffa26da..8798738d90 100644
--- a/include/mbgl/style/layers/fill_extrusion_layer.hpp
+++ b/include/mbgl/style/layers/fill_extrusion_layer.hpp
@@ -19,21 +19,6 @@ public:
     FillExtrusionLayer(const std::string& layerID, const std::string& sourceID);
     ~FillExtrusionLayer() final;
 
-    // Source
-    const std::string& getSourceID() const;
-    const std::string& getSourceLayer() const;
-    void setSourceLayer(const std::string& sourceLayer);
-
-    void setFilter(const Filter&);
-    const Filter& getFilter() const;
-
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -90,6 +75,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     FillExtrusionLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/fill_layer.hpp b/include/mbgl/style/layers/fill_layer.hpp
index 25c46d312f..033b451abc 100644
--- a/include/mbgl/style/layers/fill_layer.hpp
+++ b/include/mbgl/style/layers/fill_layer.hpp
@@ -19,21 +19,6 @@ public:
     FillLayer(const std::string& layerID, const std::string& sourceID);
     ~FillLayer() final;
 
-    // Source
-    const std::string& getSourceID() const;
-    const std::string& getSourceLayer() const;
-    void setSourceLayer(const std::string& sourceLayer);
-
-    void setFilter(const Filter&);
-    const Filter& getFilter() const;
-
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -90,6 +75,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     FillLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/heatmap_layer.hpp b/include/mbgl/style/layers/heatmap_layer.hpp
index 347bb8a4aa..2315eac3f2 100644
--- a/include/mbgl/style/layers/heatmap_layer.hpp
+++ b/include/mbgl/style/layers/heatmap_layer.hpp
@@ -20,21 +20,6 @@ public:
     HeatmapLayer(const std::string& layerID, const std::string& sourceID);
     ~HeatmapLayer() final;
 
-    // Source
-    const std::string& getSourceID() const;
-    const std::string& getSourceLayer() const;
-    void setSourceLayer(const std::string& sourceLayer);
-
-    void setFilter(const Filter&);
-    const Filter& getFilter() const;
-
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -79,6 +64,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     HeatmapLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/hillshade_layer.hpp b/include/mbgl/style/layers/hillshade_layer.hpp
index 697d4c71ad..4c18b5ed89 100644
--- a/include/mbgl/style/layers/hillshade_layer.hpp
+++ b/include/mbgl/style/layers/hillshade_layer.hpp
@@ -19,16 +19,6 @@ public:
     HillshadeLayer(const std::string& layerID, const std::string& sourceID);
     ~HillshadeLayer() final;
 
-    // Source
-    const std::string& getSourceID() const;
-
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -79,6 +69,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     HillshadeLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/layer.hpp.ejs b/include/mbgl/style/layers/layer.hpp.ejs
index 9d595d2035..f6dd08000a 100644
--- a/include/mbgl/style/layers/layer.hpp.ejs
+++ b/include/mbgl/style/layers/layer.hpp.ejs
@@ -35,25 +35,6 @@ public:
 <% } -%>
     ~<%- camelize(type) %>Layer() final;
 
-<% if (type !== 'background') { -%>
-    // Source
-    const std::string& getSourceID() const;
-<% if (type !== 'raster' && type !== 'hillshade') { -%>
-    const std::string& getSourceLayer() const;
-    void setSourceLayer(const std::string& sourceLayer);
-
-    void setFilter(const Filter&);
-    const Filter& getFilter() const;
-<% } -%>
-
-<% } -%>
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -86,6 +67,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     <%- camelize(type) %>Layer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/line_layer.hpp b/include/mbgl/style/layers/line_layer.hpp
index 1e55561bbd..0e1d026e74 100644
--- a/include/mbgl/style/layers/line_layer.hpp
+++ b/include/mbgl/style/layers/line_layer.hpp
@@ -22,21 +22,6 @@ public:
     LineLayer(const std::string& layerID, const std::string& sourceID);
     ~LineLayer() final;
 
-    // Source
-    const std::string& getSourceID() const;
-    const std::string& getSourceLayer() const;
-    void setSourceLayer(const std::string& sourceLayer);
-
-    void setFilter(const Filter&);
-    const Filter& getFilter() const;
-
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -135,6 +120,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     LineLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/raster_layer.hpp b/include/mbgl/style/layers/raster_layer.hpp
index b1c716c17f..2d10d65914 100644
--- a/include/mbgl/style/layers/raster_layer.hpp
+++ b/include/mbgl/style/layers/raster_layer.hpp
@@ -19,16 +19,6 @@ public:
     RasterLayer(const std::string& layerID, const std::string& sourceID);
     ~RasterLayer() final;
 
-    // Source
-    const std::string& getSourceID() const;
-
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -91,6 +81,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     RasterLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/style/layers/symbol_layer.hpp b/include/mbgl/style/layers/symbol_layer.hpp
index 6d82e5df85..b75a943be0 100644
--- a/include/mbgl/style/layers/symbol_layer.hpp
+++ b/include/mbgl/style/layers/symbol_layer.hpp
@@ -21,21 +21,6 @@ public:
     SymbolLayer(const std::string& layerID, const std::string& sourceID);
     ~SymbolLayer() final;
 
-    // Source
-    const std::string& getSourceID() const;
-    const std::string& getSourceLayer() const;
-    void setSourceLayer(const std::string& sourceLayer);
-
-    void setFilter(const Filter&);
-    const Filter& getFilter() const;
-
-    // Visibility
-    void setVisibility(VisibilityType) final;
-
-    // Zoom range
-    void setMinZoom(float) final;
-    void setMaxZoom(float) final;
-
     // Dynamic properties
     optional<conversion::Error> setLayoutProperty(const std::string& name, const conversion::Convertible& value) final;
     optional<conversion::Error> setPaintProperty(const std::string& name, const conversion::Convertible& value) final;
@@ -284,6 +269,9 @@ public:
     Mutable<Impl> mutableImpl() const;
     SymbolLayer(Immutable<Impl>);
     std::unique_ptr<Layer> cloneRef(const std::string& id) const final;
+
+protected:
+    Mutable<Layer::Impl> mutableBaseImpl() const final;
 };
 
 template <>
diff --git a/include/mbgl/util/immutable.hpp b/include/mbgl/util/immutable.hpp
index eb26c0d282..b4117166dd 100644
--- a/include/mbgl/util/immutable.hpp
+++ b/include/mbgl/util/immutable.hpp
@@ -39,6 +39,7 @@ private:
 
     template <class S> friend class Immutable;
     template <class S, class... Args> friend Mutable<S> makeMutable(Args&&...);
+    template <class S, class U> friend Mutable<S> staticMutableCast(const Mutable<U>&);
 };
 
 template <class T, class... Args>
@@ -46,6 +47,11 @@ Mutable<T> makeMutable(Args&&... args) {
     return Mutable<T>(std::make_shared<T>(std::forward<Args>(args)...));
 }
 
+template <class S, class U>
+Mutable<S> staticMutableCast(const Mutable<U>& u) {
+    return Mutable<S>(std::static_pointer_cast<S>(u.ptr));
+}
+
 /**
  * `Immutable<T>` is a non-nullable shared reference to a `const T`. Construction requires
  * a transfer of unique ownership from a `Mutable<T>`; once constructed it has the same behavior