[C++-sig] Wrapping and Passing HWND with Boost.Python

[Niall Douglas]

Cython is the easiest. But using the C API for this is extremely 
easy. Just pull the integer and cast to size_t and then void *.

Niall

On 1 May 2012 at 10:21, Ehsan Pi wrote:

> Thanks Niall for your response and correction on HWND.
> I'm new to Python (and Boost.Python for that matter) and thought Python was
> not typed. If not, how can one convert Python integers to void*? Googled
> but didn't find an answer.
> 
> Regards,
> Ehsan
> 
> 
> On Tue, May 1, 2012 at 9:18 AM, Niall Douglas <s_sourceforge at nedprod.com>wrote:
> 
> > A HWND is always a void * i.e. an opaque pointer. Unfortunately some
> > people using BPL think that BPL can't handle opaque pointers, so they
> > do fun stuff like use a thunk struct type for void * instead, and
> > wrap the lot in manual pointer casting. It's far easier just to
> > declare it an opaque pointer and be done with it.
> >
> > It is very unfortunate indeed that win32gui returns a HWND as an
> > integer. It isn't an integer and must not be treated as one. Still,
> > it's easy to write a routine which converts python integers to void
> > *.
> >
> > Niall
> >
> >
> > On 30 Apr 2012 at 14:54, Ehsan Pi wrote:
> >
> > > Thanks Roman for your quick reply,
> > >
> > > That's what confuses me. HWND is essentially a pointer to an int to hold
> > > the window handle. How can to convert them to each other?
> > >
> > > Ehsan
> > >
> > > On Mon, Apr 30, 2012 at 2:46 PM, Roman Yakovenko
> > > <roman.yakovenko at gmail.com>wrote:
> > >
> > > > On Mon, Apr 30, 2012 at 9:11 PM, Ehsan Pi <ehsanpii at gmail.com> wrote:
> > > > > In python I get the not-match error:
> > > > >
> > > > >     >>> import MyWrapper
> > > > >     >>> import win32gui
> > > > >     >>> hwnd = win32gui.GetDesktopWindow()
> > > > >     >>> foo = MyWrapper.Foo(hwnd)
> > > > >     Traceback (most recent call last):
> > > > >       File "<stdin>", line 1, in <module>
> > > > >     Boost.Python.ArgumentError: Python argument types in
> > > > >         Foo.__init__(Foo, int)
> > > > >     did not match C++ signature:
> > > > >         __init__(struct _object *, struct HWND__ * window)
> > > > >     >>>
> > > > >
> > > > > How can I correct this problem to be able to pass a window's handle
> > (from
> > > > > win32gui) in Python to C++ class, and interact with it?
> > > >
> > > > I think the error is pretty clear: the exported constructor expects a
> > > > pointer to some struct(?) HWND__, while, win32gui returns the handle
> > > > as integer. You will have to find some way to associate handle as
> > > > integer with handle as HWND__.  Once you find it, you can use
> > > > "make_constructor" functionality, which is also supported by py++.
> > > >
> > > > HTH.
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> > >
> >
> >
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