Optimize parameter passing to avoid unnecessary copying

src/engine.cpp

@@ -42,6 +42,7 @@
 #include <glm/glm.hpp>
 #include <unordered_set>
 #include <functional>
+#include <utility>
 
 static debug::Logger logger("engine");
 
@@ -347,11 +348,11 @@ double Engine::getDelta() const {
 void Engine::setScreen(std::shared_ptr<Screen> screen) {
     audio::reset_channel(audio::get_channel_index("regular"));
     audio::reset_channel(audio::get_channel_index("ambient"));
-    this->screen = screen;
+    this->screen = std::move(screen);
 }
 
 void Engine::setLanguage(std::string locale) {
-    langs::setup(paths->getResources(), locale, contentPacks);
+    langs::setup(paths->getResources(), std::move(locale), contentPacks);
     gui->getMenu()->setPageLoader(menus::create_page_loader(this));
 }
 
@@ -391,7 +392,7 @@ std::shared_ptr<Screen> Engine::getScreen() {
     return screen;
 }
 
-void Engine::postRunnable(runnable callback) {
+void Engine::postRunnable(const runnable& callback) {
     std::lock_guard<std::recursive_mutex> lock(postRunnablesMutex);
     postRunnables.push(callback);
 }