Re: boost::shared_ptr<T> and Gtk::TreeModelColumn<T>

[Edd Dawson <edd nunswithguns net>]

Paul Davis wrote:
> any opinions on the best way to have:
>
> 	Gtk::TreeModelColumn<boost::shared_ptr<T> > 
>
> at the moment, g++ appears to pick the void* partial specialization of
> TreeModelColumn, which leads to problems later (glib complains that the
> object is not actually a G_TYPE_POINTER etc). i have considered
> implementing another partial specialization, but I am not sure it will
> solve the issue. any thoughts?

Perhaps:

// uncompiled/untested
template<typename T>
class thin_ptr_wrapper
{
	public:
		typedef boost::shared_ptr<T> ptr_type;
		typedef boost::shared_ptr<const T> const_ptr_type;

		thin_ptr_wrapper(const ptr_type &p) : p_(p) { }
		ptr_type &operator->() { return p_; }
		const_ptr_type &operator->() const { return p_; }
		// etc...

	private:
		ptr_type p_;
};

And then use a Gtk::TreeModelColumn<thin_ptr_wrapper<T> > instead?
I'm sure there's probably a better solution, though.

I'm not sure why the void* specialization is used, though. AFAIK 
boost::shared_ptr only has a conversion operator to an 'unspecified boolean 
type', which I believe is commonly implemented as a pointer-to-member-function.

Edd