[core] Loading images to style optimization

This change enables attaching images to the style with batches and
avoids massive re-allocations. Thus, it improves UI performance
especially at start-up time.

5 files changed, 46 insertions, 42 deletions

diff --git a/src/mbgl/sprite/sprite_loader.cpp b/src/mbgl/sprite/sprite_loader.cpp
index d4b1cade13..56f7abd50b 100644
--- a/src/mbgl/sprite/sprite_loader.cpp
+++ b/src/mbgl/sprite/sprite_loader.cpp
@@ -90,7 +90,7 @@ void SpriteLoader::emitSpriteLoadedIfComplete() {
     loader->worker.self().invoke(&SpriteLoaderWorker::parse, loader->image, loader->json);
 }
 
-void SpriteLoader::onParsed(std::vector<std::unique_ptr<style::Image>>&& result) {
+void SpriteLoader::onParsed(std::vector<Immutable<style::Image::Impl>> result) {
     observer->onSpriteLoaded(std::move(result));
 }
 
diff --git a/src/mbgl/sprite/sprite_loader.hpp b/src/mbgl/sprite/sprite_loader.hpp
index 0b7d37fa14..d82c51e2da 100644
--- a/src/mbgl/sprite/sprite_loader.hpp
+++ b/src/mbgl/sprite/sprite_loader.hpp
@@ -1,6 +1,5 @@
 #pragma once
 
-#include <mbgl/util/noncopyable.hpp>
 #include <mbgl/style/image.hpp>
 
 #include <string>
@@ -15,7 +14,7 @@ namespace mbgl {
 class FileSource;
 class SpriteLoaderObserver;
 
-class SpriteLoader : public util::noncopyable {
+class SpriteLoader {
 public:
     SpriteLoader(float pixelRatio);
     ~SpriteLoader();
@@ -29,7 +28,7 @@ private:
 
     // Invoked by SpriteAtlasWorker
     friend class SpriteLoaderWorker;
-    void onParsed(std::vector<std::unique_ptr<style::Image>>&&);
+    void onParsed(std::vector<Immutable<style::Image::Impl>>);
     void onError(std::exception_ptr);
 
     const float pixelRatio;
diff --git a/src/mbgl/sprite/sprite_loader_observer.hpp b/src/mbgl/sprite/sprite_loader_observer.hpp
index c730549c2c..3846d069f0 100644
--- a/src/mbgl/sprite/sprite_loader_observer.hpp
+++ b/src/mbgl/sprite/sprite_loader_observer.hpp
@@ -1,7 +1,9 @@
 #pragma once
 
+#include <mbgl/style/image.hpp>
+#include <mbgl/util/immutable.hpp>
+
 #include <exception>
-#include <memory>
 #include <vector>
 
 namespace mbgl {
@@ -13,8 +15,7 @@ class Image;
 class SpriteLoaderObserver {
 public:
     virtual ~SpriteLoaderObserver() = default;
-
-    virtual void onSpriteLoaded(std::vector<std::unique_ptr<style::Image>>&&) {}
+    virtual void onSpriteLoaded(std::vector<Immutable<style::Image::Impl>>) {}
     virtual void onSpriteError(std::exception_ptr) {}
 };
 
diff --git a/src/mbgl/sprite/sprite_parser.cpp b/src/mbgl/sprite/sprite_parser.cpp
index d39428a848..40e63d2d7d 100644
--- a/src/mbgl/sprite/sprite_parser.cpp
+++ b/src/mbgl/sprite/sprite_parser.cpp
@@ -149,50 +149,54 @@ optional<style::ImageContent> getContent(const JSValue& value, const char* prope
 
 } // namespace
 
-std::vector<std::unique_ptr<style::Image>> parseSprite(const std::string& encodedImage, const std::string& json) {
+std::vector<Immutable<style::Image::Impl>> parseSprite(const std::string& encodedImage, const std::string& json) {
     const PremultipliedImage raster = decodeImage(encodedImage);
 
     JSDocument doc;
     doc.Parse<0>(json.c_str());
     if (doc.HasParseError()) {
         throw std::runtime_error("Failed to parse JSON: " + formatJSONParseError(doc));
-    } else if (!doc.IsObject()) {
+    }
+
+    if (!doc.IsObject()) {
         throw std::runtime_error("Sprite JSON root must be an object");
-    } else {
-        std::vector<std::unique_ptr<style::Image>> images;
-        for (const auto& property : doc.GetObject()) {
-            const std::string name = { property.name.GetString(), property.name.GetStringLength() };
-            const JSValue& value = property.value;
-
-            if (value.IsObject()) {
-                const uint16_t x = getUInt16(value, "x", name.c_str(), 0);
-                const uint16_t y = getUInt16(value, "y", name.c_str(), 0);
-                const uint16_t width = getUInt16(value, "width", name.c_str(), 0);
-                const uint16_t height = getUInt16(value, "height", name.c_str(), 0);
-                const double pixelRatio = getDouble(value, "pixelRatio", name.c_str(), 1);
-                const bool sdf = getBoolean(value, "sdf", name.c_str(), false);
-                style::ImageStretches stretchX = getStretches(value, "stretchX", name.c_str());
-                style::ImageStretches stretchY = getStretches(value, "stretchY", name.c_str());
-                optional<style::ImageContent> content = getContent(value, "content", name.c_str());
-
-                auto image = createStyleImage(name,
-                                              raster,
-                                              x,
-                                              y,
-                                              width,
-                                              height,
-                                              pixelRatio,
-                                              sdf,
-                                              std::move(stretchX),
-                                              std::move(stretchY),
-                                              std::move(content));
-                if (image) {
-                    images.push_back(std::move(image));
-                }
+    }
+
+    const auto& properties = doc.GetObject();
+    std::vector<Immutable<style::Image::Impl>> images;
+    images.reserve(properties.MemberCount());
+    for (const auto& property : properties) {
+        const std::string name = {property.name.GetString(), property.name.GetStringLength()};
+        const JSValue& value = property.value;
+
+        if (value.IsObject()) {
+            const uint16_t x = getUInt16(value, "x", name.c_str(), 0);
+            const uint16_t y = getUInt16(value, "y", name.c_str(), 0);
+            const uint16_t width = getUInt16(value, "width", name.c_str(), 0);
+            const uint16_t height = getUInt16(value, "height", name.c_str(), 0);
+            const double pixelRatio = getDouble(value, "pixelRatio", name.c_str(), 1);
+            const bool sdf = getBoolean(value, "sdf", name.c_str(), false);
+            style::ImageStretches stretchX = getStretches(value, "stretchX", name.c_str());
+            style::ImageStretches stretchY = getStretches(value, "stretchY", name.c_str());
+            optional<style::ImageContent> content = getContent(value, "content", name.c_str());
+
+            auto image = createStyleImage(name,
+                                          raster,
+                                          x,
+                                          y,
+                                          width,
+                                          height,
+                                          pixelRatio,
+                                          sdf,
+                                          std::move(stretchX),
+                                          std::move(stretchY),
+                                          std::move(content));
+            if (image) {
+                images.push_back(std::move(image->baseImpl));
             }
         }
-        return images;
     }
+    return images;
 }
 
 } // namespace mbgl
diff --git a/src/mbgl/sprite/sprite_parser.hpp b/src/mbgl/sprite/sprite_parser.hpp
index 9656bcbf2a..f2e7358ac2 100644
--- a/src/mbgl/sprite/sprite_parser.hpp
+++ b/src/mbgl/sprite/sprite_parser.hpp
@@ -20,6 +20,6 @@ std::unique_ptr<style::Image> createStyleImage(const std::string& id,
                                                optional<style::ImageContent> content = nullopt);
 
 // Parses an image and an associated JSON file and returns the sprite objects.
-std::vector<std::unique_ptr<style::Image>> parseSprite(const std::string& image, const std::string& json);
+std::vector<Immutable<style::Image::Impl>> parseSprite(const std::string& image, const std::string& json);
 
 } // namespace mbgl