[core] refactor program object creation

platform/node/src/node_mapbox_gl_native.cpp

@@ -6,12 +6,23 @@
 #pragma GCC diagnostic pop
 
 #include <mbgl/util/run_loop.hpp>
+#include <mbgl/gfx/backend.hpp>
 
 #include "node_map.hpp"
 #include "node_logging.hpp"
 #include "node_request.hpp"
 #include "node_expression.hpp"
 
+
+void SetBackendType(const Nan::FunctionCallbackInfo<v8::Value>& info) {
+    if (info.Length() < 1 || info[0]->IsUndefined()) {
+        return Nan::ThrowTypeError("Requires a render backend name");
+    }
+
+    const std::string backendName { *Nan::Utf8String(info[0]) };
+    (void)backendName;
+}
+
 void RegisterModule(v8::Local<v8::Object> target, v8::Local<v8::Object> module) {
     // This has the effect of:
     //   a) Ensuring that the static local variable is initialized before any thread contention.
@@ -19,6 +30,8 @@ void RegisterModule(v8::Local<v8::Object> target, v8::Local<v8::Object> module)
     static mbgl::util::RunLoop nodeRunLoop;
     nodeRunLoop.stop();
 
+    Nan::SetMethod(target, "setBackendType", SetBackendType);
+
     node_mbgl::NodeMap::Init(target);
     node_mbgl::NodeRequest::Init();
     node_mbgl::NodeExpression::Init(target);