[qt] Implement CustomLayerHost using a forwarding wrapper.

platform/qt/include/qmapbox.hpp

@@ -112,12 +112,16 @@ struct Q_MAPBOXGL_EXPORT CustomLayerRenderParameters {
     double zoom;
     double bearing;
     double pitch;
-    double altitude;
+    double fieldOfView;
 };
 
-typedef void (*CustomLayerInitializeFunction)(void* context) ;
-typedef void (*CustomLayerRenderFunction)(void* context, const CustomLayerRenderParameters&);
-typedef void (*CustomLayerDeinitializeFunction)(void* context);
+class Q_MAPBOXGL_EXPORT CustomLayerHostInterface {
+public:
+    virtual ~CustomLayerHostInterface() = default;
+    virtual void initialize() = 0;
+    virtual void render(const CustomLayerRenderParameters&) = 0;
+    virtual void deinitialize() = 0;
+};
 
 } // namespace QMapbox
 

platform/qt/include/qmapboxgl.hpp

@@ -223,10 +223,7 @@ class Q_MAPBOXGL_EXPORT QMapboxGL : public QObject
     void removeImage(const QString &name);
 
     void addCustomLayer(const QString &id,
-        QMapbox::CustomLayerInitializeFunction,
-        QMapbox::CustomLayerRenderFunction,
-        QMapbox::CustomLayerDeinitializeFunction,
-        void* context,
+        QScopedPointer<QMapbox::CustomLayerHostInterface>& host,
         const QString& before = QString());
     void addLayer(const QVariantMap &params, const QString& before = QString());
     bool layerExists(const QString &id);

platform/qt/src/qmapbox.cpp

@@ -158,27 +158,9 @@ namespace QMapbox {
 */
 
 /*!
-    \typedef QMapbox::CustomLayerDeinitializeFunction
+    \class QMapbox::CustomLayerHostInterface
 
-    Represents a callback to be called when destroying a custom layer.
-
-    \warning This is used for delegating the rendering of a layer to the user of
-    this API and is not officially supported. Use at your own risk.
-*/
-
-/*!
-    \typedef QMapbox::CustomLayerInitializeFunction
-
-    Represents a callback to be called when initializing a custom layer.
-
-    \warning This is used for delegating the rendering of a layer to the user of
-    this API and is not officially supported. Use at your own risk.
-*/
-
-/*!
-    \typedef QMapbox::CustomLayerRenderFunction
-
-    Represents a callback to be called on each render pass for a custom layer.
+    Represents a host interface to be implemented for rendering custom layers.
 
     \warning This is used for delegating the rendering of a layer to the user of
     this API and is not officially supported. Use at your own risk.

platform/qt/src/qmapboxgl.cpp

@@ -1343,20 +1343,43 @@ void QMapboxGL::removeSource(const QString& id)
     this API and is not officially supported. Use at your own risk.
 */
 void QMapboxGL::addCustomLayer(const QString &id,
-        QMapbox::CustomLayerInitializeFunction initFn,
-        QMapbox::CustomLayerRenderFunction renderFn,
-        QMapbox::CustomLayerDeinitializeFunction deinitFn,
-        void *context,
+        QScopedPointer<QMapbox::CustomLayerHostInterface>& host,
         const QString& before)
 {
+    class HostWrapper : public mbgl::style::CustomLayerHost {
+        public:
+        QScopedPointer<QMapbox::CustomLayerHostInterface> ptr;
+        HostWrapper(QScopedPointer<QMapbox::CustomLayerHostInterface>& p)
+         : ptr(p.take()) {
+         }
+
+        void initialize() {
+            ptr->initialize(); 
+        }
+
+        void render(const mbgl::style::CustomLayerRenderParameters& params) {
+            QMapbox::CustomLayerRenderParameters renderParams;
+            renderParams.width = params.width;
+            renderParams.height = params.height;
+            renderParams.latitude = params.latitude;
+            renderParams.longitude = params.longitude;
+            renderParams.zoom = params.zoom;
+            renderParams.bearing = params.bearing;
+            renderParams.pitch = params.pitch;
+            renderParams.fieldOfView = params.fieldOfView;
+            ptr->render(renderParams);
+        }
+
+        void contextLost() { }
+
+        void deinitialize() {
+            ptr->deinitialize();
+        }
+    };
+
     d_ptr->mapObj->getStyle().addLayer(std::make_unique<mbgl::style::CustomLayer>(
             id.toStdString(),
-            reinterpret_cast<mbgl::style::CustomLayerInitializeFunction>(initFn),
-            // This cast is safe as long as both mbgl:: and QMapbox::
-            // CustomLayerRenderParameters members remains the same.
-            (mbgl::style::CustomLayerRenderFunction)renderFn,
-            reinterpret_cast<mbgl::style::CustomLayerDeinitializeFunction>(deinitFn),
-            context),
+            std::make_unique<HostWrapper>(host)),
             before.isEmpty() ? mbgl::optional<std::string>() : mbgl::optional<std::string>(before.toStdString()));
 }