[render] Add a RunLoop to render main thread

Also simplified the code making the logic more linear.

bin/render.cpp

@@ -1,10 +1,10 @@
 #include <mbgl/map/map.hpp>
 #include <mbgl/util/image.hpp>
 #include <mbgl/util/io.hpp>
+#include <mbgl/util/run_loop.hpp>
 
 #include <mbgl/platform/default/headless_view.hpp>
 #include <mbgl/platform/default/headless_display.hpp>
-#include <mbgl/platform/log.hpp>
 #include <mbgl/storage/default_file_source.hpp>
 #include <mbgl/storage/sqlite_cache.hpp>
 
@@ -17,18 +17,9 @@
 
 namespace po = boost::program_options;
 
-#include <uv.h>
-
-#include <cassert>
 #include <cstdlib>
 #include <iostream>
 
-#if UV_VERSION_MAJOR == 0 && UV_VERSION_MINOR <= 10
-#define UV_ASYNC_PARAMS(handle) uv_async_t *handle, int
-#else
-#define UV_ASYNC_PARAMS(handle) uv_async_t *handle
-#endif
-
 int main(int argc, char *argv[]) {
     std::string style_path;
     double lat = 0, lon = 0;
@@ -73,8 +64,9 @@ int main(int argc, char *argv[]) {
 
     using namespace mbgl;
 
-    mbgl::SQLiteCache cache(cache_file);
-    mbgl::DefaultFileSource fileSource(&cache);
+    util::RunLoop loop;
+    SQLiteCache cache(cache_file);
+    DefaultFileSource fileSource(&cache);
 
     // Try to load the token from the environment.
     if (!token.size()) {
@@ -102,16 +94,7 @@ int main(int argc, char *argv[]) {
         map.setDebug(debug ? mbgl::MapDebugOptions::TileBorders | mbgl::MapDebugOptions::ParseStatus : mbgl::MapDebugOptions::NoDebug);
     }
 
-    uv_async_t *async = new uv_async_t;
-    uv_async_init(uv_default_loop(), async, [](UV_ASYNC_PARAMS(as)) {
-        std::unique_ptr<PremultipliedImage> image(reinterpret_cast<PremultipliedImage*>(as->data));
-        uv_close(reinterpret_cast<uv_handle_t *>(as), [](uv_handle_t *handle) {
-            delete reinterpret_cast<uv_async_t *>(handle);
-        });
-        util::write_file(output, encodePNG(*image));
-    });
-
-    map.renderStill([async](std::exception_ptr error, PremultipliedImage&& image) {
+    map.renderStill([&](std::exception_ptr error, PremultipliedImage&& image) {
         try {
             if (error) {
                 std::rethrow_exception(error);
@@ -121,10 +104,11 @@ int main(int argc, char *argv[]) {
             exit(1);
         }
 
-        async->data = new PremultipliedImage(std::move(image));
-        uv_async_send(async);
+        util::write_file(output, encodePNG(image));
+        loop.stop();
     });
 
-    // This loop will terminate once the async was fired.
-    uv_run(uv_default_loop(), UV_RUN_DEFAULT);
+    loop.run();
+
+    return 0;
 }