expose log messages to node.js

binding.gyp

@@ -13,6 +13,8 @@
         'src/mbgl.cpp',
         'src/compress_png.hpp',
         'src/compress_png.cpp',
+        'src/node_log.hpp',
+        'src/node_log.cpp',
         'src/node_file_source.hpp',
         'src/node_file_source.cpp',
         'src/node_map.hpp',

src/mbgl.cpp

@@ -3,9 +3,11 @@
 
 #include "node_file_source.hpp"
 #include "node_map.hpp"
+#include "node_log.hpp"
 #include "node_request.hpp"
 #include "compress_png.hpp"
 
+
 void RegisterModule(v8::Handle<v8::Object> exports) {
     NanScope();
 
@@ -23,6 +25,13 @@ void RegisterModule(v8::Handle<v8::Object> exports) {
     resource->ForceSet(NanNew("Image"), NanNew(mbgl::Resource::Image), ConstantProperty);
     resource->ForceSet(NanNew("JSON"), NanNew(mbgl::Resource::JSON), ConstantProperty);
     exports->ForceSet(NanNew("Resource"), resource, ConstantProperty);
+
+    // Make the exported object inerhit from process.EventEmitter
+    auto process = NanGetCurrentContext()->Global()->Get(NanNew("process"))->ToObject();
+    auto EventEmitter = process->Get(NanNew("EventEmitter"))->ToObject();
+    exports->SetPrototype(EventEmitter->Get(NanNew("prototype")));
+
+    mbgl::Log::Set<node_mbgl::NodeLogBackend>(exports);
 }
 
 NODE_MODULE(mbgl, RegisterModule)

src/node_log.cpp

@@ -0,0 +1,61 @@
+#include "node_log.hpp"
+
+#include <cstdarg>
+
+namespace node_mbgl {
+
+struct NodeLogBackend::Message {
+    mbgl::EventSeverity severity;
+    mbgl::Event event;
+    int64_t code;
+    std::string text;
+};
+
+NodeLogBackend::NodeLogBackend(v8::Handle<v8::Object> target)
+    : queue(new Queue(uv_default_loop(), [this](Message &message) {
+          NanScope();
+
+          auto msg = v8::Object::New();
+          msg->Set(NanNew("class"), NanNew(mbgl::EventClass(message.event).c_str()));
+          msg->Set(NanNew("severity"), NanNew(mbgl::EventSeverityClass(message.severity).c_str()));
+          if (!message.text.empty()) {
+              msg->Set(NanNew("text"), NanNew(message.text));
+          }
+          if (message.code != 0) {
+              msg->Set(NanNew("code"), NanNew(double(message.code)));
+          }
+
+          v8::Local<v8::Value> argv[] = { NanNew("message"), msg };
+          auto emit = module->Get(NanNew("emit"))->ToObject();
+          emit->CallAsFunction(module, 2, argv);
+      })) {
+    NanScope();
+    module = v8::Persistent<v8::Object>::New(target);
+}
+
+NodeLogBackend::~NodeLogBackend() {
+    queue->stop();
+}
+
+void NodeLogBackend::record(mbgl::EventSeverity severity, mbgl::Event event, const std::string &msg) {
+    queue->send({ severity, event, 0, msg });
+}
+
+void NodeLogBackend::record(mbgl::EventSeverity severity, mbgl::Event event, const char* format, ...) {
+    char msg[512];
+    va_list args;
+    va_start(args, format);
+    vsnprintf(msg, 512, format, args);
+    va_end(args);
+    queue->send({ severity, event, 0, msg });
+}
+
+void NodeLogBackend::record(mbgl::EventSeverity severity, mbgl::Event event, int64_t code) {
+    queue->send({ severity, event, code, "" });
+}
+
+void NodeLogBackend::record(mbgl::EventSeverity severity, mbgl::Event event, int64_t code, const std::string &msg) {
+    queue->send({ severity, event, code, msg });
+}
+
+}

src/node_log.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <mbgl/platform/log.hpp>
+#include <mbgl/util/async_queue.hpp>
+
+#include <node.h>
+#include <nan.h>
+
+namespace mbgl { namespace util { template <typename T> class AsyncQueue; } }
+
+namespace node_mbgl {
+
+class NodeLogBackend : public mbgl::LogBackend {
+public:
+    NodeLogBackend(v8::Handle<v8::Object> target);
+    ~NodeLogBackend();
+
+    void record(mbgl::EventSeverity severity, mbgl::Event event, const std::string &msg);
+    void record(mbgl::EventSeverity severity, mbgl::Event event, const char* format, ...);
+    void record(mbgl::EventSeverity severity, mbgl::Event event, int64_t code);
+    void record(mbgl::EventSeverity severity, mbgl::Event event, int64_t code, const std::string &msg);
+
+private:
+    v8::Persistent<v8::Object> module;
+
+    struct Message;
+    using Queue = mbgl::util::AsyncQueue<Message>;
+    Queue *queue = nullptr;
+};
+
+
+}