[Qt-interest] typedef on the same underlying type and Q_REGISTER_METATYPE

[MARTIN Pierre]

> You need to define the operators, yes. But remember you must have concrete 
> classes, not typedefs to template instantiations.
Here you go, here is what i have done so far, it seems to be working. i probably have forgot most of the "functional" operator overloading, but the idea works. Sorry for formatting, the customer i'm working for provides a VM for development and it's visual studio =/
If you see problems with this code, i'd be gratefull for you to tell me. What important CopyCtors / Assignement OPs could be missing?

#ifndef DECLARE_TYPE_WRAPPER
#define DECLARE_TYPE_WRAPPER(Cls, typ)			\
	class Cls : public RE::TypeWrapper<typ> {			\
	public:												\
		Cls ()					: TypeWrapper()	{}	\
		Cls (double const &t)	: TypeWrapper(t)	{}	\
		Cls (Cls const &c)		: TypeWrapper(c)	{}	\
	};
#endif

template<typename T>
class TypeWrapper {
public:
	// Constructors.
						TypeWrapper			()							: _t()		{}
						TypeWrapper			(T const &t)				: _t(t)		{}
						TypeWrapper			(TypeWrapper<T> const &w)	: _t(w._t)	{}
	
	// Cast operators.
						operator T			() const								{ return _t; }
	
	// Assignment operators.
	TypeWrapper<T>&		operator=			(T const &t)							{ _t = t; return *this; }
	
	// QDataStream friend serialization stuff.
	friend QDataStream&	operator<<		(QDataStream& s, TypeWrapper<T> const &w)	{ return s << w._t; }
	friend QDataStream&	operator>>		(QDataStream& s, TypeWrapper<T> &w)			{ return s >> w._t; }

private:
	T					_t;
};


Then to declare my types:
namespace T {
	DECLARE_TYPE_WRAPPER			(Ratio, double);
	DECLARE_TYPE_WRAPPER			(PositiveRatio, double);
	DECLARE_TYPE_WRAPPER			(NegativeRatio, double);
}
Q_DECLARE_TYPEINFO(RE::T::Ratio, Q_MOVABLE_TYPE);
Q_DECLARE_METATYPE(RE::T::Ratio);
Q_DECLARE_TYPEINFO(RE::T::PositiveRatio, Q_MOVABLE_TYPE);
Q_DECLARE_METATYPE(RE::T::PositiveRatio);
Q_DECLARE_METATYPE(RE::T::NegativeRatio);
Q_DECLARE_TYPEINFO(RE::T::NegativeRatio, Q_MOVABLE_TYPE);

i didn't test too much, but at least it compiles, so feel free to reuse this.


> The MOVABLE is to tell QVector and QList that they can memcpy this type with 
> impunity.
Thanks ;)

Pierre.


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