From ff09c94d0825f5dbe7dddce52b64e74d61978976 Mon Sep 17 00:00:00 2001
From: Mikhail Pozdnyakov <mikhail.pozdnyakov@mapbox.com>
Date: Thu, 15 Nov 2018 15:47:25 +0200
Subject: [core][android] Introduce mbgl::style::LayerTypeInfo

The `LayerTypeInfo` contains static meta data about certain layer type.

Each layer module should have a single immutable `LayerTypeInfo` instance
for the represented layer type. Both `LayerImpl` and `LayerFactory` from the
module always refer to the same `LayerTypeInfo` instance, so address of this
instance can be used as a layer module Id during the process life time.
---
 include/mbgl/style/layer.hpp | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

(limited to 'include/mbgl/style/layer.hpp')

diff --git a/include/mbgl/style/layer.hpp b/include/mbgl/style/layer.hpp
index 1e1e97dd0d..21ed3adbce 100644
--- a/include/mbgl/style/layer.hpp
+++ b/include/mbgl/style/layer.hpp
@@ -18,6 +18,21 @@ namespace style {
 class LayerObserver;
 class Filter;
 
+/**
+ * @brief Holds static data for a certain layer type.
+ */
+struct LayerTypeInfo {
+    /**
+     * @brief contains the layer type as defined in the style specification;
+     */
+    const char* type;
+    /**
+     * @brief contains \c SourceRequired if the corresponding layer type requires source;
+     * contains \c SourceNotRequired otherwise.
+     */
+    const enum { SourceRequired, SourceNotRequired } source;
+};
+
 /**
  * The runtime representation of a [layer](https://www.mapbox.com/mapbox-gl-style-spec/#layers) from the Mapbox Style
  * Specification.
@@ -83,12 +98,16 @@ public:
     // identical platform-native peers.
     util::peer peer;
     Layer(Immutable<Impl>);
+
+    const LayerTypeInfo* getTypeInfo() const noexcept;
+
 protected:
     virtual Mutable<Impl> mutableBaseImpl() const = 0;
 
     LayerObserver* observer;
 };
 
+
 /**
  * @brief The LayerFactory abstract class
  * 
@@ -97,8 +116,8 @@ protected:
 class LayerFactory {
 public:
     virtual ~LayerFactory() = default;
-    /// Returns \c true if this factory can produce layers of the given type of the layers; returns \c false otherwise.
-    virtual bool supportsType(const std::string& type) const noexcept = 0;
+    /// Returns the layer type data.
+    virtual const LayerTypeInfo* getTypeInfo() const noexcept = 0;
     /// Returns a new Layer instance on success call; returns `nulltptr` otherwise. 
     virtual std::unique_ptr<Layer> createLayer(const std::string& id, const conversion::Convertible& value) = 0;
 
-- 
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