[android] Convert GeoJSON features to tiles in background

Composing tiles from the GeoJSON features is an expensive
operation that might block UI thread on updating the `GeoJsonSource`
with the new data.

This change moves tile composing to the background thread and thus
unblocks the UI thread.

4 files changed, 56 insertions, 51 deletions

diff --git a/include/mbgl/style/sources/geojson_source.hpp b/include/mbgl/style/sources/geojson_source.hpp
index c8dc65b912..549393e9b2 100644
--- a/include/mbgl/style/sources/geojson_source.hpp
+++ b/include/mbgl/style/sources/geojson_source.hpp
@@ -60,6 +60,7 @@ public:
     void setGeoJSONData(std::shared_ptr<GeoJSONData>);
 
     optional<std::string> getURL() const;
+    const GeoJSONOptions& getOptions() const;
 
     class Impl;
     const Impl& impl() const;
diff --git a/platform/android/src/style/sources/geojson_source.cpp b/platform/android/src/style/sources/geojson_source.cpp
index 5ff4864275..0eece4b1ad 100644
--- a/platform/android/src/style/sources/geojson_source.cpp
+++ b/platform/android/src/style/sources/geojson_source.cpp
@@ -44,18 +44,16 @@ namespace android {
     }
 
     GeoJSONSource::GeoJSONSource(jni::JNIEnv& env, const jni::String& sourceId, const jni::Object<>& options)
-        : Source(env, std::make_unique<mbgl::style::GeoJSONSource>(
-                jni::Make<std::string>(env, sourceId),
-                convertGeoJSONOptions(env, options)))
-        , converter(std::make_unique<Actor<FeatureConverter>>(Scheduler::GetBackground())) {
-    }
+        : Source(env,
+                 std::make_unique<mbgl::style::GeoJSONSource>(jni::Make<std::string>(env, sourceId),
+                                                              convertGeoJSONOptions(env, options))),
+          converter(std::make_unique<Actor<FeatureConverter>>(Scheduler::GetBackground(),
+                                                              source.as<style::GeoJSONSource>()->getOptions())) {}
 
-    GeoJSONSource::GeoJSONSource(jni::JNIEnv& env,
-                                 mbgl::style::Source& coreSource,
-                                 AndroidRendererFrontend& frontend)
-        : Source(env, coreSource, createJavaPeer(env), frontend)
-        , converter(std::make_unique<Actor<FeatureConverter>>(Scheduler::GetBackground())) {
-    }
+    GeoJSONSource::GeoJSONSource(jni::JNIEnv& env, mbgl::style::Source& coreSource, AndroidRendererFrontend& frontend)
+        : Source(env, coreSource, createJavaPeer(env), frontend),
+          converter(std::make_unique<Actor<FeatureConverter>>(Scheduler::GetBackground(),
+                                                              source.as<style::GeoJSONSource>()->getOptions())) {}
 
     GeoJSONSource::~GeoJSONSource() = default;
 
@@ -63,7 +61,7 @@ namespace android {
 
         std::shared_ptr<std::string> json = std::make_shared<std::string>(jni::Make<std::string>(env, jString));
 
-        Update::Converter converterFn = [this, json](ActorRef<Callback> _callback) {
+        Update::Converter converterFn = [this, json](ActorRef<GeoJSONDataCallback> _callback) {
             converter->self().invoke(&FeatureConverter::convertJson, json, _callback);
         };
 
@@ -84,11 +82,11 @@ namespace android {
 
     void GeoJSONSource::setURL(jni::JNIEnv& env, const jni::String& url) {
         // Update the core source
-        source.as<mbgl::style::GeoJSONSource>()->GeoJSONSource::setURL(jni::Make<std::string>(env, url));
+        source.as<style::GeoJSONSource>()->setURL(jni::Make<std::string>(env, url));
     }
 
     jni::Local<jni::String> GeoJSONSource::getURL(jni::JNIEnv& env) {
-        optional<std::string> url = source.as<mbgl::style::GeoJSONSource>()->GeoJSONSource::getURL();
+        optional<std::string> url = source.as<style::GeoJSONSource>()->getURL();
         return url ? jni::Make<jni::String>(env, *url) : jni::Local<jni::String>();
     }
 
@@ -166,7 +164,7 @@ namespace android {
         auto global = jni::NewGlobal<jni::EnvAttachingDeleter>(env, jObject);
         auto object = std::make_shared<decltype(global)>(std::move(global));
 
-        Update::Converter converterFn = [this, object](ActorRef<Callback> _callback) {
+        Update::Converter converterFn = [this, object](ActorRef<GeoJSONDataCallback> _callback) {
             converter->self().invoke(&FeatureConverter::convertObject<JNIType>, object, _callback);
         };
 
@@ -175,25 +173,23 @@ namespace android {
 
     void GeoJSONSource::setAsync(Update::Converter converterFn) {
         awaitingUpdate = std::make_unique<Update>(
-                std::move(converterFn),
-                std::make_unique<Actor<Callback>>(
-                        *Scheduler::GetCurrent(),
-                        [this](GeoJSON geoJSON) {
-                            // conversion from Java features to core ones finished
-                            android::UniqueEnv _env = android::AttachEnv();
-
-                            // Update the core source
-                            source.as<mbgl::style::GeoJSONSource>()->GeoJSONSource::setGeoJSON(geoJSON);
-
-                            // if there is an awaiting update, execute it, otherwise, release resources
-                            if (awaitingUpdate) {
-                                update = std::move(awaitingUpdate);
-                                update->converterFn(update->callback->self());
-                            } else {
-                                update.reset();
-                            }
-                        })
-        );
+            std::move(converterFn),
+            std::make_unique<Actor<GeoJSONDataCallback>>(
+                *Scheduler::GetCurrent(), [this](std::shared_ptr<style::GeoJSONData> geoJSONData) {
+                    // conversion from Java features to core ones finished
+                    android::UniqueEnv _env = android::AttachEnv();
+
+                    // Update the core source
+                    source.as<mbgl::style::GeoJSONSource>()->setGeoJSONData(std::move(geoJSONData));
+
+                    // if there is an awaiting update, execute it, otherwise, release resources
+                    if (awaitingUpdate) {
+                        update = std::move(awaitingUpdate);
+                        update->converterFn(update->callback->self());
+                    } else {
+                        update.reset();
+                    }
+                }));
 
         // If another update is running, wait
         if (update) {
@@ -230,12 +226,10 @@ namespace android {
         );
     }
 
-    void FeatureConverter::convertJson(std::shared_ptr<std::string> json,
-                                       ActorRef<Callback> callback) {
+    void FeatureConverter::convertJson(std::shared_ptr<std::string> json, ActorRef<GeoJSONDataCallback> callback) {
         using namespace mbgl::style::conversion;
 
         android::UniqueEnv _env = android::AttachEnv();
-
         // Convert the jni object
         Error error;
         optional<GeoJSON> converted = parseGeoJSON(*json, error);
@@ -243,23 +237,23 @@ namespace android {
             mbgl::Log::Error(mbgl::Event::JNI, "Error setting geo json: " + error.message);
             return;
         }
-
-        callback.invoke(&Callback::operator(), *converted);
+        callback.invoke(&GeoJSONDataCallback::operator(), style::GeoJSONData::create(*converted, options));
     }
 
     template <class JNIType>
-    void FeatureConverter::convertObject(std::shared_ptr<jni::Global<jni::Object<JNIType>, jni::EnvAttachingDeleter>> jObject, ActorRef<Callback> callback) {
+    void FeatureConverter::convertObject(
+        std::shared_ptr<jni::Global<jni::Object<JNIType>, jni::EnvAttachingDeleter>> jObject,
+        ActorRef<GeoJSONDataCallback> callback) {
         using namespace mbgl::android::geojson;
 
         android::UniqueEnv _env = android::AttachEnv();
         // Convert the jni object
         auto geometry = JNIType::convert(*_env, *jObject);
-        callback.invoke(&Callback::operator(), GeoJSON(geometry));
+        callback.invoke(&GeoJSONDataCallback::operator(), style::GeoJSONData::create(geometry, options));
     }
 
-    Update::Update(Converter _converterFn, std::unique_ptr<Actor<Callback>> _callback)
-            : converterFn(std::move(_converterFn))
-            , callback(std::move(_callback)) {}
+    Update::Update(Converter _converterFn, std::unique_ptr<Actor<GeoJSONDataCallback>> _callback)
+        : converterFn(std::move(_converterFn)), callback(std::move(_callback)) {}
 
 } // namespace android
 } // namespace mbgl
diff --git a/platform/android/src/style/sources/geojson_source.hpp b/platform/android/src/style/sources/geojson_source.hpp
index e737e41924..e506191ceb 100644
--- a/platform/android/src/style/sources/geojson_source.hpp
+++ b/platform/android/src/style/sources/geojson_source.hpp
@@ -11,22 +11,28 @@
 namespace mbgl {
 namespace android {
 
-using Callback = std::function<void (GeoJSON)>;
+using GeoJSONDataCallback = std::function<void(std::shared_ptr<style::GeoJSONData>)>;
 
-struct FeatureConverter {
-    void convertJson(std::shared_ptr<std::string>, ActorRef<Callback>);
+class FeatureConverter {
+public:
+    explicit FeatureConverter(style::GeoJSONOptions options_) : options(std::move(options_)) {}
+    void convertJson(std::shared_ptr<std::string>, ActorRef<GeoJSONDataCallback>);
 
     template <class JNIType>
-    void convertObject(std::shared_ptr<jni::Global<jni::Object<JNIType>, jni::EnvAttachingDeleter>>, ActorRef<Callback>);
+    void convertObject(std::shared_ptr<jni::Global<jni::Object<JNIType>, jni::EnvAttachingDeleter>>,
+                       ActorRef<GeoJSONDataCallback>);
+
+private:
+    style::GeoJSONOptions options;
 };
 
 struct Update {
-    using Converter = std::function<void (ActorRef<Callback>)>;
+    using Converter = std::function<void(ActorRef<GeoJSONDataCallback>)>;
     Converter converterFn;
 
-    std::unique_ptr<Actor<Callback>> callback;
+    std::unique_ptr<Actor<GeoJSONDataCallback>> callback;
 
-    Update(Converter, std::unique_ptr<Actor<Callback>>);
+    Update(Converter, std::unique_ptr<Actor<GeoJSONDataCallback>>);
 };
 
 class GeoJSONSource : public Source {
diff --git a/src/mbgl/style/sources/geojson_source.cpp b/src/mbgl/style/sources/geojson_source.cpp
index 79e7c23459..3832977cd4 100644
--- a/src/mbgl/style/sources/geojson_source.cpp
+++ b/src/mbgl/style/sources/geojson_source.cpp
@@ -45,6 +45,10 @@ optional<std::string> GeoJSONSource::getURL() const {
     return url;
 }
 
+const GeoJSONOptions& GeoJSONSource::getOptions() const {
+    return impl().getOptions();
+}
+
 void GeoJSONSource::loadDescription(FileSource& fileSource) {
     if (!url) {
         loaded = true;