Added covers, cross-fade

src/ScriptEngine.cpp

@@ -240,6 +240,33 @@ namespace ZL {
                 std::cerr << "[script] rotate_object: object '" << name << "' not found\n";
             });
 
+        // fade_object(name, target_alpha, duration_sec [, on_complete])
+        api.set_function("fade_object",
+            [game](const std::string& name, float targetAlpha,
+                   float durationSec, sol::object onComplete) {
+                for (auto& intObj : game->interactiveObjects) {
+                    if (intObj.loadedObject.name != name) continue;
+                    if (intObj.isAnimating) {
+                        std::cerr << "[script] fade_object: '" << name << "' is already animating\n";
+                        return;
+                    }
+                    std::function<void()> cb;
+                    if (onComplete.is<sol::protected_function>()) {
+                        sol::protected_function fn = onComplete.as<sol::protected_function>();
+                        cb = [fn]() mutable {
+                            auto res = fn();
+                            if (!res.valid()) {
+                                sol::error err = res;
+                                std::cerr << "[script] fade_object on_complete error: " << err.what() << "\n";
+                            }
+                        };
+                    }
+                    intObj.fadeTo(targetAlpha, durationSec, std::move(cb));
+                    return;
+                }
+                std::cerr << "[script] fade_object: object '" << name << "' not found\n";
+            });
+
         // scale_object(name, target_scale, duration_sec [, on_complete])
         api.set_function("scale_object",
             [game](const std::string& name, float targetScale,