[PyKDE] PyQt 4 doesn't allow to create an application, given an already open display. How to solve it?

[Phil Thompson]

On Thursday 08 March 2007 8:40 am, Matt Newell wrote:
> On Thursday 08 March 2007 00:07, Ulrich Berning wrote:
> > mikos at centrum.cz wrote:
> > >Eh, I have just realized that I have replied directly to Phil Thompson,
> > > not to this list (this is because I have used unfamiliar webmail
> > > client). So this is our conversation:
> > >
> > >*** Me: ***
> > >You can look at that example by Zack Rusin, it is very simple, here is
> > > code: http://ktown.kde.org/~zrusin/examples/argb.tar.bz2 (look at
> > > main.cpp)
> > >
> > >That Display instance come directly from xlib, it is created by
> > > XOpenDisplay: http://lxr.freedesktop.org/ident?i=XOpenDisplay
> > >
> > >In Python, I am using ctypes module to directly access xlib (libX11)
> > >and call XOpenDisplay.
> > >
> > >*** Phil: ***
> > >I meant, in the context of PyQt. PyQt needs to know about the type.
> > >
> > >*** Me: ***
> > >I can't help you much in this, I don't know much about ctypes, I have
> > > only learned it because I want to create ARGB windows with PyQt (and
> > > then I realized that I can't do it because PyQt doesn't support it).
> > > But you can try this code:
> > >
> > >### Python code ###
> > >import ctypes
> > >
> > >class Display(ctypes.Structure):
> > >pass
> > >
> > >xlib = ctypes.CDLL('libX11.so.6')
> > >xlib.XOpenDisplay.restype = ctypes.POINTER(Display)
> > >xlib.XOpenDisplay.argtypes = [ctypes.c_char_p]
> > >
> > >display = xlib.XOpenDisplay(':0.0')
> > >### End of Python code ###
> > >
> > >This will create 'display' object, which is pointer to 'Display'
> > > structure (which is derived from standard ctypes.Structure).
> > >
> > >But this is all I can tell you, as I said I don't know any details about
> > > this process, only that it works (I have tried creating window with
> > > pure xlib).
> > >
> > >Ctypes are standard module in python 2.5 (for Python 2.4 it is external
> > >module), so I think PyQt should support it.
> >
> > The ctypes extension doesn't build on AIX, HP-UX, IRIX and Solaris. With
> > some changes, it may build on IRIX and Solaris, because libffi has been
> > ported to these platforms. On AIX and HP-UX, you have definitely lost.
> > I've never understood, why ctypes became a standard module.
> >
> > PyQt works on the above platforms. Making it dependent on the ctypes
> > extension seems to be a bad idea.
>
> Display is just a pointer.  I think PyQt could support accepting a ctypes
> pointer as an arguement without depending on ctypes being available.  The
> ctypes pointer is simply passed as a PyObject * and regular python api
> calls are used to check that it is indeed a ctypes pointer, and to get the
> value.

Ironically ctypes doesn't provide the necessary C API to do this. However if 
(in Python) you can get the address of the real data structure as a number 
(ctypes.addressof() ?) then you can create a sip.voidptr from it and I can 
add the ctors to accept that.

Phil