replace Style object immediately

this makes sure that adding custom sprite imagery will add them to the new Style object rather than
the old one in case a user adds new custom sprites immediately after changing a stylesheet

src/mbgl/map/map_context.cpp

@@ -99,6 +99,8 @@ void MapContext::setStyleURL(const std::string& url) {
     styleURL = url;
     styleJSON.clear();
 
+    style = std::make_unique<Style>(data, asyncUpdate->get()->loop);
+
     const size_t pos = styleURL.rfind('/');
     std::string base = "";
     if (pos != std::string::npos) {
@@ -120,14 +122,15 @@ void MapContext::setStyleJSON(const std::string& json, const std::string& base)
     styleURL.clear();
     styleJSON = json;
 
+    style = std::make_unique<Style>(data, asyncUpdate->get()->loop);
+
     loadStyleJSON(json, base);
 }
 
 void MapContext::loadStyleJSON(const std::string& json, const std::string& base) {
     assert(util::ThreadContext::currentlyOn(util::ThreadType::Map));
 
-    style.reset();
-    style = std::make_unique<Style>(json, base, data, asyncUpdate->get()->loop);
+    style->setJSON(json, base);
     style->cascade(data.getClasses());
     style->setDefaultTransitionDuration(data.getDefaultTransitionDuration());
     style->setObserver(this);
@@ -376,7 +379,10 @@ void MapContext::onLowMemory() {
 }
 
 void MapContext::setSprite(const std::string& name, std::shared_ptr<const SpriteImage> sprite) {
-    if (!style) return;
+    if (!style) {
+        Log::Info(Event::Sprite, "Ignoring sprite without stylesheet");
+        return;
+    }
 
     style->spriteStore->setSprite(name, sprite);
 

src/mbgl/style/style.cpp

@@ -22,8 +22,7 @@
 
 namespace mbgl {
 
-Style::Style(const std::string& json, const std::string&, MapData& data_,
-             uv_loop_t* loop)
+Style::Style(MapData& data_, uv_loop_t* loop)
     : data(data_),
       glyphStore(std::make_unique<GlyphStore>(loop)),
       glyphAtlas(std::make_unique<GlyphAtlas>(1024, 1024)),
@@ -32,7 +31,10 @@ Style::Style(const std::string& json, const std::string&, MapData& data_,
       lineAtlas(std::make_unique<LineAtlas>(512, 512)),
       mtx(std::make_unique<uv::rwlock>()),
       workers(4) {
+    glyphStore->setObserver(this);
+}
 
+void Style::setJSON(const std::string& json, const std::string&) {
     rapidjson::Document doc;
     doc.Parse<0>((const char *const)json.c_str());
     if (doc.HasParseError()) {
@@ -55,8 +57,6 @@ Style::Style(const std::string& json, const std::string&, MapData& data_,
         source->setObserver(this);
         source->load();
     }
-
-    glyphStore->setObserver(this);
 }
 
 Style::~Style() {

src/mbgl/style/style.hpp

@@ -32,9 +32,7 @@ class Style : public GlyphStore::Observer,
               public Sprite::Observer,
               public util::noncopyable {
 public:
-    Style(const std::string& data,
-          const std::string& base,
-          MapData&,
+    Style(MapData&,
           uv_loop_t*);
     ~Style();
 
@@ -46,6 +44,8 @@ public:
         virtual void onResourceLoadingFailed(std::exception_ptr error) = 0;
     };
 
+    void setJSON(const std::string& data, const std::string& base);
+
     void setObserver(Observer*);
 
     bool isLoaded() const;

test/style/resource_loading.cpp

@@ -32,7 +32,8 @@ public:
         transform_.setLatLngZoom({0, 0}, 16);
 
         const std::string style = util::read_file("test/fixtures/resources/style.json");
-        style_ = std::make_unique<Style>(style, "", data_, util::RunLoop::getLoop());
+        style_ = std::make_unique<Style>(data_, util::RunLoop::getLoop());
+        style_->setJSON(style, "");
         style_->setObserver(this);
     }