[core] Use an actor model for tile worker concurrency

src/mbgl/tile/raster_tile.cpp

@@ -1,4 +1,5 @@
 #include <mbgl/tile/raster_tile.hpp>
+#include <mbgl/tile/raster_tile_worker.hpp>
 #include <mbgl/tile/tile_observer.hpp>
 #include <mbgl/tile/tile_loader_impl.hpp>
 #include <mbgl/style/source.hpp>
@@ -6,8 +7,8 @@
 #include <mbgl/storage/resource.hpp>
 #include <mbgl/storage/response.hpp>
 #include <mbgl/storage/file_source.hpp>
-#include <mbgl/util/worker.hpp>
-#include <mbgl/util/work_request.hpp>
+#include <mbgl/renderer/raster_bucket.hpp>
+#include <mbgl/util/run_loop.hpp>
 
 namespace mbgl {
 
@@ -15,13 +16,20 @@ RasterTile::RasterTile(const OverscaledTileID& id_,
                        const style::UpdateParameters& parameters,
                        const Tileset& tileset)
     : Tile(id_),
-      worker(parameters.worker),
-      loader(*this, id_, parameters, tileset) {
+      loader(*this, id_, parameters, tileset),
+      mailbox(std::make_shared<Mailbox>(*util::RunLoop::Get())),
+      worker(parameters.workerScheduler,
+             ActorRef<RasterTile>(*this, mailbox)) {
 }
 
 RasterTile::~RasterTile() = default;
 
+void RasterTile::cancel() {
+}
+
 void RasterTile::setError(std::exception_ptr err) {
+    bucket.reset();
+    availableData = DataAvailability::All;
     observer->onTileError(*this, err);
 }
 
@@ -30,30 +38,13 @@ void RasterTile::setData(std::shared_ptr<const std::string> data,
                              optional<Timestamp> expires_) {
     modified = modified_;
     expires = expires_;
+    worker.invoke(&RasterTileWorker::parse, data);
+}
 
-    if (!data) {
-        // This is a 404 response. We're treating these as empty tiles.
-        workRequest.reset();
-        availableData = DataAvailability::All;
-        bucket.reset();
-        observer->onTileLoaded(*this, TileLoadState::First);
-        return;
-    }
-
-    workRequest.reset();
-    workRequest = worker.parseRasterTile(std::make_unique<RasterBucket>(), data, [this] (RasterTileParseResult result) {
-        workRequest.reset();
-
-        availableData = DataAvailability::All;
-
-        if (result.is<std::unique_ptr<Bucket>>()) {
-            bucket = std::move(result.get<std::unique_ptr<Bucket>>());
-            observer->onTileLoaded(*this, TileLoadState::First);
-        } else {
-            bucket.reset();
-            observer->onTileError(*this, result.get<std::exception_ptr>());
-        }
-    });
+void RasterTile::onParsed(std::unique_ptr<Bucket> result) {
+    bucket = std::move(result);
+    availableData = DataAvailability::All;
+    observer->onTileChanged(*this);
 }
 
 Bucket* RasterTile::getBucket(const style::Layer&) {
@@ -64,8 +55,4 @@ void RasterTile::setNecessity(Necessity necessity) {
     loader.setNecessity(necessity);
 }
 
-void RasterTile::cancel() {
-    workRequest.reset();
-}
-
 } // namespace mbgl