[PyQt] Re: QStyle manipulations

[Hans-Peter Jansen]

Am Montag, 27. Juli 2009 schrieb Phil Thompson:
> On Mon, 27 Jul 2009 22:56:57 +0200, "Hans-Peter Jansen" <hpj at urpla.net>
>
> wrote:
> > Am Montag, 27. Juli 2009 schrieb Phil Thompson:
> >> On Mon, 27 Jul 2009 21:03:59 +0200, "Hans-Peter Jansen"
> >> <hpj at urpla.net>
> >>
> >> >>     const_cast<QStyle
> >> >> *>(this)->qt_metacall(QMetaObject::InvokeMetaMethod,
> >> >> d->layoutSpacingIndex, param); return result;
> >> >> }
> >> >>
> >> >>
> >> >> Do you see any chance of getting this to behave?
> >> >
> >> > Hmm, from what I can see (though I _am_ blind, when it comes to the
> >> > guts from sip and PyQt), most of needed mechanics is in place. The
> >> > question
> >>
> >> is,
> >>
> >> > what have to be done, that:
> >> >  * the metaObject is able to locate our method with
> >> >    metaObject()->indexOfMethod(), and
> >> >  * qt_metacall is able to invoke our method
> >> >
> >> > The former may already do what it should (otherwise parts of the
> >> > QMetaObject
> >> > stuff won't do at all, it's even wrapped in qobjectdefs.sip).
> >> >
> >> > The latter seems to be the problem, since it may need some kind of
> >> >
> >> >
> >> > Parts of qpy/QtCore/qpycore_pyqtproxy.cpp look like they handle
>
> similar
>
> >> > cases. Is it possible to register our method at run-time and be done
> >> > with
> >> >
> >> > it, Phil?
> >>
> >> You can certainly work around the problem with C++ code - but I'm not
> >> sure if SIP will allow you to place the C++ code in the right place.
> >
> > Hmm, as it stands, I'm lost in a maze of Qt meta object system wrapped
> > in
> >
> > the guts of sip and PyQt. It looks like it takes some kind of manual
> > registration in the Q*Style constructor on C++ level, which is normally
> > covered in the Q_OBJECT macro, but I've no idea, how it all fits
> > together
> >
> > conceptually, thus unable to come up with some kind of solution to the
> > problem. Will try to solve the problem differently, uglier, much
> > uglier. Rarely I regret to be a Python guy, like today :-(.
>
> You may get away with a Python implementation by sub-classing the QStyle
> you want to modify and using the pyqtSlot decorator on the method you
> want Qt to call.

Tried that already, without success. Qt dispatches the call to 
layoutSpacingImplementation() in QStyle.layoutSpacing(). I also tried to 
intercept that, but since it is not virtual, that does not work, either.
(That's the whole reason for these metaObject games, Qt playes here).

I already intercepted a couple of other methods, but none allows reducing 
the spacing. There's another QStyle method, which may fit: 
combinedLayoutSpacing, but that cannot be intercepted either (because, it 
is not virtual).

The basic problem I try to solve, is that I've created a typical QWidget 
based sub class of a combined QCheckBox and QToolButton. And while on my 
Linux desktop with QPlastiqueStyle the spacing is well (similar to other 
widgets, on the Mac with QMacStyle the vertical spacing of those custom 
widgets is nearly twice as high as ordinary check boxes. I've tried to 
control the margins from within my widget, but the margins are controlled 
via private QWidget methods and attributes - unreachable from PyQt.

Pete
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