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void setup_printer(
  GtkPageOrientation orientation, 
  gdouble top, gdouble bottom, gdouble left, gdouble right, 
  GtkUnit unit
);

uint8_t* render(
  const uint8_t *html, 
  size_t html_length, 
  size_t *length // Out

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static void uv_cb(uv_async_t *handle) {
    auto p = (payload *)handle->data;
    auto isolate = Isolate::GetCurrent();
    HandleScope handle_scope(isolate);

    const unsigned argc = 2;
    Local<Value> argv[argc];

    argv[0] = Null(isolate);
    argv[1] = Nan::NewBuffer((char*)p->data, p->data_length).ToLocalChecked(); // This transfers ownership of p->data to Node

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void done(uint8_t* data, size_t data_length) {
    auto p = new payload();
    p->data = data;
    p->data_length = data_length;
    p->func = &func;
    p->work_ref = this;

    handle->data = (void *)p;
    uv_async_send(handle);
}

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// Structure of this is borrowed from https://gist.github.com/matzoe/11082417
class WorkItem {
    typedef struct payload {
        v8_persistent_copyable_function *func;
        WorkItem *work_ref;
        uint8_t *data; // I own this but I will give it away later
        size_t data_length;
    } payload;

    uv_async_t *handle; // I own this, play nice with libuv before freeing.

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void init(Handle <Object> exports, Handle<Object> module) {
    NODE_SET_METHOD(exports, "start", start);
    NODE_SET_METHOD(exports, "render", render);
}

NODE_MODULE(PDFRenderer, init)

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typedef Persistent<Function, CopyablePersistentTraits<Function>> v8_persistent_copyable_function;

void render(const FunctionCallbackInfo<Value>& args) {
    auto isolate = args.GetIsolate();

    // Arg 0 is our html in a buffer
    // Arg 1 is our callback
    auto func = v8_persistent_copyable_function(Isolate::GetCurrent(), Local<Function>::Cast(args[1]));
    auto html = args[0]->ToObject();
    auto html_data = node::Buffer::Data(html);

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void start(const FunctionCallbackInfo<Value>& args) {
    auto isolate = args.GetIsolate();

    debug_print("Starting background thread\n");
    int err = 0;
    err = uv_mutex_init(&work_mutex);
    if (err < 0) {
        isolate->ThrowException(Exception::Error(String::NewFromUtf8(isolate, "Could not create uv mutex.")));
        return;
    }

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std::queue<WorkItem*> work_queue;
uv_mutex_t work_mutex;

void worker_thread(void *arg) {
    // TODO: This should be configurable from Node
    setup_printer(
        GTK_PAGE_ORIENTATION_PORTRAIT,
        0.5, 0.5, 0.5, 0.5,
        GTK_UNIT_INCH
    );

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uint8_t *render(const uint8_t *html, size_t html_length, size_t *length);
void setup_printer(GtkPageOrientation orientation, gdouble top, gdouble bottom, gdouble left, gdouble right, GtkUnit unit);

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uint8_t *render(const uint8_t *html, size_t html_length, size_t *length) {
    load_web_view(html, html_length);

    gtk_main();
    debug_print("done loop\n");

    std::string filename;
    do_print(filename);

    debug_print("Sending filename %s back\n", filename.c_str());