Change: [Script] Automate the ScriptObject reference counting

src/script/api/script_object.hpp

@@ -21,6 +21,8 @@
 #include "../script_suspend.hpp"
 #include "../squirrel.hpp"
 
+#include <utility>
+
 /**
  * The callback function for Mode-classes.
  */
@@ -367,4 +369,68 @@ bool ScriptObject::ScriptDoCommandHelper<Tcmd, Tret(*)(DoCommandFlag, Targs...)>
 	}
 }
 
+/**
+ * Internally used class to automate the ScriptObject reference counting.
+ * @api -all
+ */
+template <typename T>
+class ScriptObjectRef {
+private:
+	T *data; ///< The reference counted object.
+public:
+	/**
+	 * Create the reference counter for the given ScriptObject instance.
+	 * @param data The underlying object.
+	 */
+	ScriptObjectRef(T *data) : data(data)
+	{
+		this->data->AddRef();
+	}
+
+	/* No copy constructor. */
+	ScriptObjectRef(const ScriptObjectRef<T> &ref) = delete;
+
+	/* Move constructor. */
+	ScriptObjectRef(ScriptObjectRef<T> &&ref) noexcept : data(std::exchange(ref.data, nullptr))
+	{
+	}
+
+	/* No copy assignment. */
+	ScriptObjectRef& operator=(const ScriptObjectRef<T> &other) = delete;
+
+	/* Move assignment. */
+	ScriptObjectRef& operator=(ScriptObjectRef<T> &&other) noexcept
+	{
+		std::swap(this->data, other.data);
+		return *this;
+	}
+
+	/**
+	 * Release the reference counted object.
+	 */
+	~ScriptObjectRef()
+	{
+		if (this->data != nullptr) this->data->Release();
+	}
+
+	/**
+	 * Dereferencing this reference returns a reference to the reference
+	 * counted object
+	 * @return Reference to the underlying object.
+	 */
+	T &operator*()
+	{
+		return *this->data;
+	}
+
+	/**
+	 * The arrow operator on this reference returns the reference counted object.
+	 * @return Pointer to the underlying object.
+	 */
+	T *operator->()
+	{
+		return this->data;
+	}
+};
+
 #endif /* SCRIPT_OBJECT_HPP */

src/script/api/script_text.cpp

@@ -53,19 +53,10 @@ ScriptText::ScriptText(HSQUIRRELVM vm) :
 	}
 }
 
-ScriptText::~ScriptText()
-{
-	for (int i = 0; i < SCRIPT_TEXT_MAX_PARAMETERS; i++) {
-		if (std::holds_alternative<ScriptText *>(this->param[i])) std::get<ScriptText *>(this->param[i])->Release();
-	}
-}
-
 SQInteger ScriptText::_SetParam(int parameter, HSQUIRRELVM vm)
 {
 	if (parameter >= SCRIPT_TEXT_MAX_PARAMETERS) return SQ_ERROR;
 
-	if (std::holds_alternative<ScriptText *>(this->param[parameter])) std::get<ScriptText *>(this->param[parameter])->Release();
-
 	switch (sq_gettype(vm, -1)) {
 		case OT_STRING: {
 			const SQChar *value;
@@ -102,8 +93,7 @@ SQInteger ScriptText::_SetParam(int parameter, HSQUIRRELVM vm)
 			if (real_instance == nullptr) return SQ_ERROR;
 
 			ScriptText *value = static_cast<ScriptText *>(real_instance);
-			value->AddRef();
-			this->param[parameter] = value;
+			this->param[parameter] = ScriptTextRef(value);
 			break;
 		}
 
@@ -184,9 +174,9 @@ char *ScriptText::_GetEncodedText(char *p, char *lastofp, int &param_count)
 			param_count++;
 			continue;
 		}
-		if (std::holds_alternative<ScriptText *>(this->param[i])) {
+		if (std::holds_alternative<ScriptTextRef>(this->param[i])) {
 			p += seprintf(p, lastofp, ":");
-			p = std::get<ScriptText *>(this->param[i])->_GetEncodedText(p, lastofp, param_count);
+			p = std::get<ScriptTextRef>(this->param[i])->_GetEncodedText(p, lastofp, param_count);
 			continue;
 		}
 		p += seprintf(p, lastofp, ":" OTTD_PRINTFHEX64, std::get<SQInteger>(this->param[i]));

src/script/api/script_text.hpp

@@ -90,7 +90,6 @@ public:
 	 */
 	ScriptText(StringID string, ...);
 #endif /* DOXYGEN_API */
-	~ScriptText();
 
 #ifndef DOXYGEN_API
 	/**
@@ -129,8 +128,10 @@ public:
 	virtual const std::string GetEncodedText();
 
 private:
+	using ScriptTextRef = ScriptObjectRef<ScriptText>;
+
 	StringID string;
-	std::variant<SQInteger, std::string, ScriptText *> param[SCRIPT_TEXT_MAX_PARAMETERS];
+	std::variant<SQInteger, std::string, ScriptTextRef> param[SCRIPT_TEXT_MAX_PARAMETERS];
 	int paramc;
 
 	/**