[core] Move Sprite parsing to thread pool

6 files changed, 97 insertions, 35 deletions

diff --git a/src/mbgl/sprite/sprite_atlas.cpp b/src/mbgl/sprite/sprite_atlas.cpp
index bdccf289df..3b774b627a 100644
--- a/src/mbgl/sprite/sprite_atlas.cpp
+++ b/src/mbgl/sprite/sprite_atlas.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/sprite/sprite_atlas.hpp>
+#include <mbgl/sprite/sprite_atlas_worker.hpp>
 #include <mbgl/sprite/sprite_atlas_observer.hpp>
 #include <mbgl/sprite/sprite_parser.hpp>
 #include <mbgl/gl/context.hpp>
@@ -11,6 +12,8 @@
 #include <mbgl/storage/file_source.hpp>
 #include <mbgl/storage/resource.hpp>
 #include <mbgl/storage/response.hpp>
+#include <mbgl/util/run_loop.hpp>
+#include <mbgl/actor/actor.hpp>
 
 #include <cassert>
 #include <cmath>
@@ -21,10 +24,17 @@ namespace mbgl {
 static SpriteAtlasObserver nullObserver;
 
 struct SpriteAtlas::Loader {
+    Loader(Scheduler& scheduler, SpriteAtlas& spriteAtlas)
+        : mailbox(std::make_shared<Mailbox>(*util::RunLoop::Get())),
+          worker(scheduler, ActorRef<SpriteAtlas>(spriteAtlas, mailbox)) {
+    }
+
     std::shared_ptr<const std::string> image;
     std::shared_ptr<const std::string> json;
     std::unique_ptr<AsyncRequest> jsonRequest;
     std::unique_ptr<AsyncRequest> spriteRequest;
+    std::shared_ptr<Mailbox> mailbox;
+    Actor<SpriteAtlasWorker> worker;
 };
 
 SpriteAtlasElement::SpriteAtlasElement(Rect<uint16_t> rect_,
@@ -56,14 +66,14 @@ SpriteAtlas::SpriteAtlas(Size size_, float pixelRatio_)
 
 SpriteAtlas::~SpriteAtlas() = default;
 
-void SpriteAtlas::load(const std::string& url, FileSource& fileSource) {
+void SpriteAtlas::load(const std::string& url, Scheduler& scheduler, FileSource& fileSource) {
     if (url.empty()) {
         // Treat a non-existent sprite as a successfully loaded empty sprite.
-        loaded = true;
+        markAsLoaded();
         return;
     }
 
-    loader = std::make_unique<Loader>();
+    loader = std::make_unique<Loader>(scheduler, *this);
 
     loader->jsonRequest = fileSource.request(Resource::spriteJSON(url, pixelRatio), [this](Response res) {
         if (res.error) {
@@ -102,18 +112,22 @@ void SpriteAtlas::emitSpriteLoadedIfComplete() {
         return;
     }
 
-    auto result = parseSprite(*loader->image, *loader->json);
-    if (result.is<Sprites>()) {
-        loaded = true;
-        setSprites(result.get<Sprites>());
-        observer->onSpriteLoaded();
-        for (auto requestor : requestors) {
-            requestor->onIconsAvailable(this, buildIconMap());
-        }
-        requestors.clear();
-    } else {
-        observer->onSpriteError(result.get<std::exception_ptr>());
+    loader->worker.invoke(&SpriteAtlasWorker::parse, loader->image, loader->json);
+    // TODO: delete the loader?
+}
+
+void SpriteAtlas::onParsed(Sprites&& result) {
+    markAsLoaded();
+    setSprites(result);
+    observer->onSpriteLoaded();
+    for (auto requestor : requestors) {
+        requestor->onIconsAvailable(this, buildIconMap());
     }
+    requestors.clear();
+}
+
+void SpriteAtlas::onError(std::exception_ptr err) {
+    observer->onSpriteError(err);
 }
 
 void SpriteAtlas::setObserver(SpriteAtlasObserver* observer_) {
diff --git a/src/mbgl/sprite/sprite_atlas.hpp b/src/mbgl/sprite/sprite_atlas.hpp
index 3c37f57708..21df25d67d 100644
--- a/src/mbgl/sprite/sprite_atlas.hpp
+++ b/src/mbgl/sprite/sprite_atlas.hpp
@@ -15,6 +15,7 @@
 
 namespace mbgl {
 
+class Scheduler;
 class FileSource;
 class SpriteAtlasObserver;
 
@@ -56,7 +57,11 @@ public:
     SpriteAtlas(Size, float pixelRatio);
     ~SpriteAtlas();
 
-    void load(const std::string& url, FileSource&);
+    void load(const std::string& url, Scheduler&, FileSource&);
+
+    void markAsLoaded() {
+        loaded = true;
+    }
 
     bool isLoaded() const {
         return loaded;
@@ -97,6 +102,10 @@ private:
     void _setSprite(const std::string&, const std::shared_ptr<const SpriteImage>& = nullptr);
     void emitSpriteLoadedIfComplete();
 
+    // Invoked by SpriteAtlasWorker
+    friend class SpriteAtlasWorker;
+    void onParsed(Sprites&& result);
+    void onError(std::exception_ptr);
 
     const Size size;
     const float pixelRatio;
diff --git a/src/mbgl/sprite/sprite_atlas_worker.cpp b/src/mbgl/sprite/sprite_atlas_worker.cpp
new file mode 100644
index 0000000000..da507aabab
--- /dev/null
+++ b/src/mbgl/sprite/sprite_atlas_worker.cpp
@@ -0,0 +1,29 @@
+#include <mbgl/sprite/sprite_atlas_worker.hpp>
+#include <mbgl/sprite/sprite_atlas.hpp>
+#include <mbgl/sprite/sprite_parser.hpp>
+
+namespace mbgl {
+
+SpriteAtlasWorker::SpriteAtlasWorker(ActorRef<SpriteAtlasWorker>, ActorRef<SpriteAtlas> parent_)
+    : parent(std::move(parent_)) {
+}
+
+void SpriteAtlasWorker::parse(std::shared_ptr<const std::string> image,
+                              std::shared_ptr<const std::string> json) {
+    try {
+        if (!image) {
+            // This shouldn't happen, since we always invoke it with a non-empty pointer.
+            throw std::runtime_error("missing sprite image");
+        }
+        if (!json) {
+            // This shouldn't happen, since we always invoke it with a non-empty pointer.
+            throw std::runtime_error("missing sprite metadata");
+        }
+
+        parent.invoke(&SpriteAtlas::onParsed, parseSprite(*image, *json));
+    } catch (...) {
+        parent.invoke(&SpriteAtlas::onError, std::current_exception());
+    }
+}
+
+} // namespace mbgl
diff --git a/src/mbgl/sprite/sprite_atlas_worker.hpp b/src/mbgl/sprite/sprite_atlas_worker.hpp
new file mode 100644
index 0000000000..70ca0d52e5
--- /dev/null
+++ b/src/mbgl/sprite/sprite_atlas_worker.hpp
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <mbgl/actor/actor_ref.hpp>
+#include <mbgl/sprite/sprite_parser.hpp>
+
+#include <memory>
+#include <string>
+
+namespace mbgl {
+
+class SpriteAtlas;
+
+class SpriteAtlasWorker {
+public:
+    SpriteAtlasWorker(ActorRef<SpriteAtlasWorker>, ActorRef<SpriteAtlas>);
+
+    void parse(std::shared_ptr<const std::string> image, std::shared_ptr<const std::string> json);
+
+private:
+    ActorRef<SpriteAtlas> parent;
+};
+
+} // namespace mbgl
diff --git a/src/mbgl/sprite/sprite_parser.cpp b/src/mbgl/sprite/sprite_parser.cpp
index 66b5ec0606..96a883b0dd 100644
--- a/src/mbgl/sprite/sprite_parser.cpp
+++ b/src/mbgl/sprite/sprite_parser.cpp
@@ -84,26 +84,19 @@ bool getBoolean(const JSValue& value, const char* name, const bool def = false)
 
 } // namespace
 
-SpriteParseResult parseSprite(const std::string& image, const std::string& json) {
-    Sprites sprites;
-    PremultipliedImage raster;
-
-    try {
-        raster = decodeImage(image);
-    } catch (...) {
-        return std::current_exception();
-    }
+Sprites parseSprite(const std::string& image, const std::string& json) {
+    const PremultipliedImage raster = decodeImage(image);
 
     JSDocument doc;
     doc.Parse<0>(json.c_str());
-
     if (doc.HasParseError()) {
         std::stringstream message;
         message << "Failed to parse JSON: " << rapidjson::GetParseError_En(doc.GetParseError()) << " at offset " << doc.GetErrorOffset();
-        return std::make_exception_ptr(std::runtime_error(message.str()));
+        throw std::runtime_error(message.str());
     } else if (!doc.IsObject()) {
-        return std::make_exception_ptr(std::runtime_error("Sprite JSON root must be an object"));
+        throw std::runtime_error("Sprite JSON root must be an object");
     } else {
+        Sprites sprites;
         for (const auto& property : doc.GetObject()) {
             const std::string name = { property.name.GetString(), property.name.GetStringLength() };
             const JSValue& value = property.value;
@@ -122,9 +115,8 @@ SpriteParseResult parseSprite(const std::string& image, const std::string& json)
                 }
             }
         }
+        return sprites;
     }
-
-    return sprites;
 }
 
 } // namespace mbgl
diff --git a/src/mbgl/sprite/sprite_parser.hpp b/src/mbgl/sprite/sprite_parser.hpp
index 4a63d4858a..9e462f324e 100644
--- a/src/mbgl/sprite/sprite_parser.hpp
+++ b/src/mbgl/sprite/sprite_parser.hpp
@@ -26,12 +26,7 @@ SpriteImagePtr createSpriteImage(const PremultipliedImage&,
 
 using Sprites = std::map<std::string, SpriteImagePtr>;
 
-
-using SpriteParseResult = variant<
-    Sprites,             // success
-    std::exception_ptr>; // error
-
 // Parses an image and an associated JSON file and returns the sprite objects.
-SpriteParseResult parseSprite(const std::string& image, const std::string& json);
+Sprites parseSprite(const std::string& image, const std::string& json);
 
 } // namespace mbgl