[node] Change Map/FileSource relationship to composition

platform/node/src/node_map.cpp

@@ -615,14 +615,14 @@ void NodeMap::cancel() {
         reinterpret_cast<NodeMap *>(h->data)->renderFinished();
     });
 
-    frontend = std::make_unique<mbgl::HeadlessFrontend>(mbgl::Size{ 256, 256 }, pixelRatio, *this, threadpool);
+    frontend = std::make_unique<mbgl::HeadlessFrontend>(mbgl::Size{ 256, 256 }, pixelRatio, fileSource, threadpool);
     mbgl::MapOptions options;
     options.withMapMode(mode)
            .withConstrainMode(mbgl::ConstrainMode::HeightOnly)
            .withViewportMode(mbgl::ViewportMode::Default)
            .withCrossSourceCollisions(crossSourceCollisions);
     map = std::make_unique<mbgl::Map>(*frontend, mapObserver, frontend->getSize(), pixelRatio,
-                                      *this, threadpool, options);
+                                      fileSource, threadpool, options);
 
     // FIXME: Reload the style after recreating the map. We need to find
     // a better way of canceling an ongoing rendering on the core level
@@ -1200,12 +1200,13 @@ NodeMap::NodeMap(v8::Local<v8::Object> options)
             : true;
     }())
     , mapObserver(NodeMapObserver())
-    , frontend(std::make_unique<mbgl::HeadlessFrontend>(mbgl::Size { 256, 256 }, pixelRatio, *this, threadpool))
+    , fileSource(this)
+    , frontend(std::make_unique<mbgl::HeadlessFrontend>(mbgl::Size { 256, 256 }, pixelRatio, fileSource, threadpool))
     , map(std::make_unique<mbgl::Map>(*frontend,
                                       mapObserver,
                                       frontend->getSize(),
                                       pixelRatio,
-                                      *this,
+                                      fileSource,
                                       threadpool,
                                       mbgl::MapOptions().withMapMode(mode)
                                                         .withConstrainMode(mbgl::ConstrainMode::HeightOnly)
@@ -1226,15 +1227,19 @@ NodeMap::~NodeMap() {
     if (map) release();
 }
 
-std::unique_ptr<mbgl::AsyncRequest> NodeMap::request(const mbgl::Resource& resource, mbgl::FileSource::Callback callback_) {
+NodeFileSource::NodeFileSource(NodeMap* nodeMap_) : nodeMap(nodeMap_) {}
+
+std::unique_ptr<mbgl::AsyncRequest> NodeFileSource::request(const mbgl::Resource& resource, mbgl::FileSource::Callback callback_) {
+    assert(nodeMap);
+
     Nan::HandleScope scope;
     // Because this method may be called while this NodeMap is already eligible for garbage collection,
     // we need to explicitly hold onto our own handle here so that GC during a v8 call doesn't destroy
     // *this while we're still executing code.
-    handle();
+    nodeMap->handle();
 
     v8::Local<v8::Value> argv[] = {
-        Nan::New<v8::External>(this),
+        Nan::New<v8::External>(nodeMap),
         Nan::New<v8::External>(&callback_)
     };
 

platform/node/src/node_map.hpp

@@ -25,10 +25,21 @@ class NodeMapObserver : public mbgl::MapObserver {
     void onDidFailLoadingMap(std::exception_ptr) override;
 };
 
+class NodeMap;
+
+class NodeFileSource : public mbgl::FileSource {
+public:
+    NodeFileSource(NodeMap*);
+
+    std::unique_ptr<mbgl::AsyncRequest> request(const mbgl::Resource&, mbgl::FileSource::Callback) final;
+
+private:
+    NodeMap* nodeMap;
+};
+
 class RenderRequest;
 
-class NodeMap : public Nan::ObjectWrap,
-                public mbgl::FileSource {
+class NodeMap : public Nan::ObjectWrap {
 public:
     struct RenderOptions;
     class RenderWorker;
@@ -78,13 +89,12 @@ public:
 
     static RenderOptions ParseOptions(v8::Local<v8::Object>);
 
-    std::unique_ptr<mbgl::AsyncRequest> request(const mbgl::Resource&, mbgl::FileSource::Callback);
-
     const float pixelRatio;
     mbgl::MapMode mode;
     bool crossSourceCollisions;
     NodeThreadPool threadpool;
     NodeMapObserver mapObserver;
+    NodeFileSource fileSource;
     std::unique_ptr<mbgl::HeadlessFrontend> frontend;
     std::unique_ptr<mbgl::Map> map;
 
@@ -98,4 +108,4 @@ public:
     bool loaded = false;
 };
 
-}
+} // namespace node_mbgl