GeoJSONSource is re-using the existing scheduler

Thus avoiding spawing new threads on `setGeoJSONData()` calls.

3 files changed, 33 insertions, 14 deletions

diff --git a/include/mbgl/style/sources/geojson_source.hpp b/include/mbgl/style/sources/geojson_source.hpp
index df2f9d2daf..750d29627d 100644
--- a/include/mbgl/style/sources/geojson_source.hpp
+++ b/include/mbgl/style/sources/geojson_source.hpp
@@ -42,7 +42,8 @@ public:
     using TileFeatures = mapbox::feature::feature_collection<int16_t>;
     using Features = mapbox::feature::feature_collection<double>;
     static std::shared_ptr<GeoJSONData> create(const GeoJSON&,
-                                               Immutable<GeoJSONOptions> = GeoJSONOptions::defaultOptions());
+                                               Immutable<GeoJSONOptions> = GeoJSONOptions::defaultOptions(),
+                                               std::shared_ptr<Scheduler> scheduler = nullptr);
 
     virtual ~GeoJSONData() = default;
     virtual void getTile(const CanonicalTileID&, const std::function<void(TileFeatures)>&) = 0;
@@ -53,6 +54,8 @@ public:
                                const std::uint32_t limit = 10u,
                                const std::uint32_t offset = 0u) = 0;
     virtual std::uint8_t getClusterExpansionZoom(std::uint32_t) = 0;
+
+    virtual std::shared_ptr<Scheduler> getScheduler() { return nullptr; }
 };
 
 class GeoJSONSource final : public Source {
diff --git a/src/mbgl/style/sources/geojson_source.cpp b/src/mbgl/style/sources/geojson_source.cpp
index d8414c1f84..3afccf07f2 100644
--- a/src/mbgl/style/sources/geojson_source.cpp
+++ b/src/mbgl/style/sources/geojson_source.cpp
@@ -39,8 +39,20 @@ void GeoJSONSource::setURL(const std::string& url_) {
     }
 }
 
+namespace {
+
+inline std::shared_ptr<GeoJSONData> createGeoJSONData(const mapbox::geojson::geojson& geoJSON,
+                                                      const GeoJSONSource::Impl& impl) {
+    if (auto data = impl.getData().lock()) {
+        return GeoJSONData::create(geoJSON, impl.getOptions(), data->getScheduler());
+    }
+    return GeoJSONData::create(geoJSON, impl.getOptions());
+}
+
+} // namespace
+
 void GeoJSONSource::setGeoJSON(const mapbox::geojson::geojson& geoJSON) {
-    setGeoJSONData(GeoJSONData::create(geoJSON, impl().getOptions()));
+    setGeoJSONData(createGeoJSONData(geoJSON, impl()));
 }
 
 void GeoJSONSource::setGeoJSONData(std::shared_ptr<GeoJSONData> geoJSONData) {
@@ -83,7 +95,7 @@ void GeoJSONSource::loadDescription(FileSource& fileSource) {
                 conversion::Error error;
                 std::shared_ptr<GeoJSONData> geoJSONData;
                 if (optional<GeoJSON> geoJSON = conversion::convertJSON<GeoJSON>(*data, error)) {
-                    geoJSONData = GeoJSONData::create(*geoJSON, current.getOptions());
+                    geoJSONData = createGeoJSONData(*geoJSON, current);
                 } else {
                     // Create an empty GeoJSON VT object to make sure we're not infinitely waiting for tiles to load.
                     Log::Error(Event::ParseStyle, "Failed to parse GeoJSON data: %s", error.message.c_str());
diff --git a/src/mbgl/style/sources/geojson_source_impl.cpp b/src/mbgl/style/sources/geojson_source_impl.cpp
index e73876b429..bb5445f02b 100644
--- a/src/mbgl/style/sources/geojson_source_impl.cpp
+++ b/src/mbgl/style/sources/geojson_source_impl.cpp
@@ -13,8 +13,7 @@
 namespace mbgl {
 namespace style {
 
-class GeoJSONVTData : public GeoJSONData {
-public:
+class GeoJSONVTData final : public GeoJSONData {
     void getTile(const CanonicalTileID& id, const std::function<void(TileFeatures)>& fn) final {
         assert(fn);
         scheduler->scheduleAndReplyValue(
@@ -29,18 +28,21 @@ public:
         return 0;
     }
 
-private:
+    std::shared_ptr<Scheduler> getScheduler() final { return scheduler; }
+
     friend GeoJSONData;
-    GeoJSONVTData(const GeoJSON& geoJSON, const mapbox::geojsonvt::Options& options)
-        : impl(std::make_shared<mapbox::geojsonvt::GeoJSONVT>(geoJSON, options)),
-          scheduler(Scheduler::GetSequenced()) {}
+    GeoJSONVTData(const GeoJSON& geoJSON,
+                  const mapbox::geojsonvt::Options& options,
+                  std::shared_ptr<Scheduler> scheduler_)
+        : impl(std::make_shared<mapbox::geojsonvt::GeoJSONVT>(geoJSON, options)), scheduler(std::move(scheduler_)) {
+        assert(scheduler);
+    }
 
     std::shared_ptr<mapbox::geojsonvt::GeoJSONVT> impl; // Accessed on worker thread.
     std::shared_ptr<Scheduler> scheduler;
 };
 
-class SuperclusterData : public GeoJSONData {
-public:
+class SuperclusterData final : public GeoJSONData {
     void getTile(const CanonicalTileID& id, const std::function<void(TileFeatures)>& fn) final {
         assert(fn);
         fn(impl.getTile(id.z, id.x, id.y));
@@ -56,7 +58,6 @@ public:
         return impl.getClusterExpansionZoom(cluster_id);
     }
 
-private:
     friend GeoJSONData;
     SuperclusterData(const Features& features, const mapbox::supercluster::Options& options)
         : impl(features, options) {}
@@ -78,7 +79,9 @@ T evaluateFeature(const mapbox::feature::feature<double>& f,
 }
 
 // static
-std::shared_ptr<GeoJSONData> GeoJSONData::create(const GeoJSON& geoJSON, Immutable<GeoJSONOptions> options) {
+std::shared_ptr<GeoJSONData> GeoJSONData::create(const GeoJSON& geoJSON,
+                                                 Immutable<GeoJSONOptions> options,
+                                                 std::shared_ptr<Scheduler> scheduler) {
     constexpr double scale = util::EXTENT / util::tileSize;
     if (options->cluster && geoJSON.is<Features>() && !geoJSON.get<Features>().empty()) {
         mapbox::supercluster::Options clusterOptions;
@@ -114,7 +117,8 @@ std::shared_ptr<GeoJSONData> GeoJSONData::create(const GeoJSON& geoJSON, Immutab
     vtOptions.buffer = ::round(scale * options->buffer);
     vtOptions.tolerance = scale * options->tolerance;
     vtOptions.lineMetrics = options->lineMetrics;
-    return std::shared_ptr<GeoJSONData>(new GeoJSONVTData(geoJSON, vtOptions));
+    if (!scheduler) scheduler = Scheduler::GetSequenced();
+    return std::shared_ptr<GeoJSONData>(new GeoJSONVTData(geoJSON, vtOptions, std::move(scheduler)));
 }
 
 GeoJSONSource::Impl::Impl(std::string id_, Immutable<GeoJSONOptions> options_)