[core] Correctly track sprite loaded state through smart setStyle

src/mbgl/renderer/image_manager.cpp

@@ -4,12 +4,23 @@
 
 namespace mbgl {
 
-void ImageManager::onSpriteLoaded() {
-    loaded = true;
-    for (const auto& entry : requestors) {
-        notify(*entry.first, entry.second);
+void ImageManager::setLoaded(bool loaded_) {
+    if (loaded == loaded_) {
+        return;
     }
-    requestors.clear();
+
+    loaded = loaded_;
+
+    if (loaded) {
+        for (const auto& entry : requestors) {
+            notify(*entry.first, entry.second);
+        }
+        requestors.clear();
+    }
+}
+
+bool ImageManager::isLoaded() const {
+    return loaded;
 }
 
 void ImageManager::addImage(Immutable<style::Image::Impl> image_) {

src/mbgl/renderer/image_manager.hpp

@@ -39,11 +39,8 @@ public:
     ImageManager();
     ~ImageManager();
 
-    void onSpriteLoaded();
-
-    bool isLoaded() const {
-        return loaded;
-    }
+    void setLoaded(bool);
+    bool isLoaded() const;
 
     void dumpDebugLogs() const;
 

src/mbgl/renderer/render_style.cpp

@@ -143,9 +143,7 @@ void RenderStyle::update(const UpdateParameters& parameters) {
         imageManager->updateImage(entry.second.after);
     }
 
-    if (parameters.spriteLoaded && !imageManager->isLoaded()) {
-        imageManager->onSpriteLoaded();
-    }
+    imageManager->setLoaded(parameters.spriteLoaded);
 
 
     const LayerDifference layerDiff = diffLayers(layerImpls, parameters.layers);

src/mbgl/style/style_impl.cpp

@@ -111,6 +111,7 @@ void Style::Impl::parse(const std::string& json_) {
     defaultPitch = parser.pitch;
     setLight(std::make_unique<Light>(parser.light));
 
+    spriteLoaded = false;
     spriteLoader->load(parser.spriteURL, scheduler, fileSource);
     glyphURL = parser.glyphURL;
 

test/renderer/image_manager.test.cpp

@@ -127,7 +127,7 @@ TEST(ImageManager, NotifiesRequestorWhenSpriteIsLoaded) {
     imageManager.getImages(requestor, {"one"});
     ASSERT_FALSE(notified);
 
-    imageManager.onSpriteLoaded();
+    imageManager.setLoaded(true);
     ASSERT_TRUE(notified);
 }