Re: [boost] Re: smart_ptr and handles

From: Jonathan Wakely (cow_at_[hidden])
Date: 2004-12-29 10:06:41

On Wed, Dec 29, 2004 at 04:44:22PM +0200, Peter Dimov wrote:

> Jonathan Wakely wrote:
> >   struct DCReleaser
> >   {
> >       DCReleaser(HWND hwnd) : hwnd(hwnd) {}
> >       void operator()(void* p) { ReleaseDC( hwnd, (HDC)p ); }
> >       HWND hwnd;
> >   };
> >
> >   handle make_dc( HWND hWnd )
> >   {
> >      return handle( GetDC( hWnd ), DCReleaser(hWnd) );
> >   }
> 
> Yep. Note also that shared_ptr will call the deleter with an HDC, not a 
> void*, so the cast in operator() is not necessary:
> 
>       void operator()(HDC p) const { ReleaseDC( hwnd, p ); }

Yes, of course it will. Silly me. Thanks, Peter.

> >I think bind(ReleaseDC, hWnd, _1) should work.
> 
> That's what I'd use, too. :-) 

Finally, Dirk, if you don't want to use shared_ptr<void> (and casts)
everywhere you can include boost/type_traits.hpp and use remove_pointer:

typedef shared_ptr<remove_pointer<HDC>::type>  dc_handle;
typedef shared_ptr<remove_pointer<HWND>::type> wnd_handle;

jon

-- 
"It is unbecoming for young men to utter maxims."
	- Aristotle