[PyQt] [PyQt3] QPen issues

[Ingmar Steen]

On 5/14/07, Hans-Peter Jansen <hpj at urpla.net> wrote:
>
> Am Montag, 14. Mai 2007 09:56 schrieb Phil Thompson:
> > On Sunday 13 May 2Hmm, shouldn't this code behave in the same way too,
> than:
>
>    void paintEvent(QPaintEvent* event)
>    {
>        QPainter p(this);
>        QPen pn=p.pen();
>        pn.setWidth(2);
>
> [found in qt3/doc/examples/progress/progress.cpp, line 85]007 4:18 pm,
> Hans-Peter Jansen wrote:
> > > Hi Phil,
> > >
> > > while at PyQt3 issues, could you look into an issue with pens, when
> > > fetching them with pen() from a QPainter. When using a QPen()
> instance,
> > > all is well, but modifying the fetched pen does not work (a pen with
> > > default properties will be used, no matter what is set on it).
> >
> > In C++ pen() returns a const reference - and SIP doesn't support const
> > except to cast it away. I don't know what the C++ compiler is supposed
> to
> > do in those circumstances - but it looks like it is just discarding any
> > attempts to modify the const QPen.
>
> Hmm, shouldn't this code behave in the same way too, than:
>
>     void paintEvent(QPaintEvent* event)
>     {
>         QPainter p(this);
>         QPen pn=p.pen();
>         pn.setWidth(2);
>
> [found in qt3/doc/examples/progress/progress.cpp, line 85]
>
> > If SIP properly supported const then you would get an exception when you
> > called setColor().
> >
> > The solution is to make a non-const copy of the pen...
> >
> >         p = QPainter(self)
> >         pn = QPen(p.pen())
> >         pn.setColor(Qt.red)
> >
> > Phil
>
> Ahh, I see. Thanks.
>
> Mind throwing the attached progress.py into examples3? Apart from a bunch
> of
> fixes, a few different default settings and menu shortcuts it much more
> resembles the current Qt version now (functional and visual wise).
>
> Cheers,
>   Pete "Retro" Jansen
>

A bit off-topic, but the reason the C++ version you referenced works is
because in C++ this will implicitly make a mutable copy of the const QPen
object using QPen's copy constructor. In python, you apparently have to do
that explicitly.

Ingmar
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