[core] Separate transition options accessors from class API

Now the style class transition options have its own getter/setter, which
persists for each style until a new style is set.

include/mbgl/map/map.hpp

@@ -51,9 +51,12 @@ public:
     void update(Update update);
 
     // Styling
-    void addClass(const std::string&, const style::TransitionOptions& = {});
-    void removeClass(const std::string&, const style::TransitionOptions& = {});
-    void setClasses(const std::vector<std::string>&, const style::TransitionOptions& = {});
+    void addClass(const std::string&);
+    void removeClass(const std::string&);
+    void setClasses(const std::vector<std::string>&);
+
+    style::TransitionOptions getTransitionOptions() const;
+    void setTransitionOptions(const style::TransitionOptions&);
 
     bool hasClass(const std::string&) const;
     std::vector<std::string> getClasses() const;

src/mbgl/map/map.cpp

@@ -896,25 +896,38 @@ bool Map::isFullyLoaded() const {
     return impl->style ? impl->style->isLoaded() : false;
 }
 
-void Map::addClass(const std::string& className, const TransitionOptions& properties) {
-    if (impl->style && impl->style->addClass(className, properties)) {
+void Map::addClass(const std::string& className) {
+    if (impl->style && impl->style->addClass(className)) {
         update(Update::Classes);
     }
 }
 
-void Map::removeClass(const std::string& className, const TransitionOptions& properties) {
-    if (impl->style && impl->style->removeClass(className, properties)) {
+void Map::removeClass(const std::string& className) {
+    if (impl->style && impl->style->removeClass(className)) {
         update(Update::Classes);
     }
 }
 
-void Map::setClasses(const std::vector<std::string>& classNames, const TransitionOptions& properties) {
+void Map::setClasses(const std::vector<std::string>& classNames) {
     if (impl->style) {
-        impl->style->setClasses(classNames, properties);
+        impl->style->setClasses(classNames);
         update(Update::Classes);
     }
 }
 
+style::TransitionOptions Map::getTransitionOptions() const {
+    if (impl->style) {
+        return impl->style->getTransitionOptions();
+    }
+    return {};
+}
+
+void Map::setTransitionOptions(const style::TransitionOptions& options) {
+    if (impl->style) {
+        impl->style->setTransitionOptions(options);
+    }
+}
+
 bool Map::hasClass(const std::string& className) const {
     return impl->style ? impl->style->hasClass(className) : false;
 }

src/mbgl/style/style.cpp

@@ -58,10 +58,9 @@ Style::~Style() {
     spriteStore->setObserver(nullptr);
 }
 
-bool Style::addClass(const std::string& className, const TransitionOptions& properties) {
+bool Style::addClass(const std::string& className) {
     if (hasClass(className)) return false;
     classes.push_back(className);
-    transitionProperties = properties;
     return true;
 }
 
@@ -69,29 +68,36 @@ bool Style::hasClass(const std::string& className) const {
     return std::find(classes.begin(), classes.end(), className) != classes.end();
 }
 
-bool Style::removeClass(const std::string& className, const TransitionOptions& properties) {
+bool Style::removeClass(const std::string& className) {
     const auto it = std::find(classes.begin(), classes.end(), className);
     if (it != classes.end()) {
         classes.erase(it);
-        transitionProperties = properties;
         return true;
     }
     return false;
 }
 
-void Style::setClasses(const std::vector<std::string>& classNames, const TransitionOptions& properties) {
+void Style::setClasses(const std::vector<std::string>& classNames) {
     classes = classNames;
-    transitionProperties = properties;
 }
 
 std::vector<std::string> Style::getClasses() const {
     return classes;
 }
 
+void Style::setTransitionOptions(const TransitionOptions& options) {
+    transitionOptions = options;
+}
+
+TransitionOptions Style::getTransitionOptions() const {
+    return transitionOptions;
+}
+
 void Style::setJSON(const std::string& json) {
     sources.clear();
     layers.clear();
     classes.clear();
+    transitionOptions = {};
     updateBatch = {};
 
     Parser parser;
@@ -249,11 +255,9 @@ void Style::cascade(const TimePoint& timePoint, MapMode mode) {
     const CascadeParameters parameters {
         classIDs,
         mode == MapMode::Continuous ? timePoint : Clock::time_point::max(),
-        mode == MapMode::Continuous ? transitionProperties.value_or(immediateTransition) : immediateTransition
+        mode == MapMode::Continuous ? transitionOptions : immediateTransition
     };
 
-    transitionProperties = {};
-
     for (const auto& layer : layers) {
         layer->baseImpl->cascade(parameters);
     }

src/mbgl/style/style.hpp

@@ -79,10 +79,14 @@ public:
     double getDefaultBearing() const;
     double getDefaultPitch() const;
 
-    bool addClass(const std::string&, const TransitionOptions& = {});
-    bool removeClass(const std::string&, const TransitionOptions& = {});
+    bool addClass(const std::string&);
+    bool removeClass(const std::string&);
+    void setClasses(const std::vector<std::string>&);
+
+    TransitionOptions getTransitionOptions() const;
+    void setTransitionOptions(const TransitionOptions&);
+
     bool hasClass(const std::string&) const;
-    void setClasses(const std::vector<std::string>&, const TransitionOptions& = {});
     std::vector<std::string> getClasses() const;
 
     RenderData getRenderData(MapDebugOptions) const;
@@ -107,7 +111,7 @@ private:
     std::vector<std::unique_ptr<Source>> sources;
     std::vector<std::unique_ptr<Layer>> layers;
     std::vector<std::string> classes;
-    optional<TransitionOptions> transitionProperties;
+    TransitionOptions transitionOptions;
 
     // Defaults
     std::string name;