[Qt-interest] Dynamic painting in a QMdiArea

[Scott Aron Bloom]

Also, you can try qobject_cast, which will always work across DLL
boundries (as opposed to dynamic_cast which may not)
Scott

> -----Original Message-----
> From: qt-interest-bounces at trolltech.com [mailto:qt-interest-
> bounces at trolltech.com] On Behalf Of Malyushytsky, Alex
> Sent: Tuesday, January 13, 2009 3:40 PM
> To: qt-interest at trolltech.com
> Subject: Re: [Qt-interest] Dynamic painting in a QMdiArea
> 
> 1. Just a wild guess.
> Do you have Run Time Type Info enabled? At least with MSVC you can
disable it
> for the project. In this case dynamic_cast always returns NULL.
> For QObject derved classes I would use QObject::inherits() instead of
> dynamic_cast.
> 
> To figure out which QWidget pointer you get you could use objectName()
and
> QMetaObject::className().
> 
> 2. Can't give any comments on second question other that I would
assume that
> viewport of QMdiArea should not depend on children (QMdiSubWindow) and
the
> line location should be defined by Pt1 and Pt2 values in your code.
> 
> Best regards,
> Alex
> 
> 
> -----Original Message-----
> From: qt-interest-bounces at trolltech.com [mailto:qt-interest-
> bounces at trolltech.com] On Behalf Of Pascal Francq
> Sent: Tuesday, January 13, 2009 2:41 PM
> To: qt-interest at trolltech.com
> Subject: Re: [Qt-interest] Dynamic painting in a QMdiArea
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> I have solve part of my problems by creating child class of QMdiArea.
I have
> still two questions.
> 
> 1. In the method 'mousePressEvent' I try to verify that the current
mouse
> position correspond to a window.
> 
>         void QMyMdiArea::mousePressEvent(QMouseEvent* event)
>         {
>                 QWidget*
ptr(viewport()->childAt(event->x(),event->y()));
>                 if(ptr)
>                         cout<<"Child"<<endl;
>                 else
>                 {
>                         cout<<"No Child"<<endl;
>                         return;
>                 }
>                 QMdiSubWindow* ptr2=dynamic_cast<QMdiSubWindow*>(ptr);
>                 if(ptr2)
>                         cout<<"Sub"<<endl;
>                 else
>                 {
>                         cout<<"No Sub"<<endl;
>                         return;
>                 }
>         }
> 
> When I click on a window, it shows me 'Child' but not 'Sub'. This
seems
> strange since all the windows I insert inherits from QMdiSubWindow
(and
> another class depending of the widget contained).
> 
> 2. When I paint a line in the area, it is paint bellow the
sub-windows. How
> can I paint it above them.
> 
>         void QMyMdiArea::paintEvent(QPaintEvent* event)
>         {
>                 QMdiArea::paintEvent(event);
>                 QPainter Painter(viewport());
>                 Painter.setPen(Qt::red);
>                 Painter.drawLine(Pt1,Pt2);
>         }
> 
> Thanks.
> 
> On mardi 13 janvier 2009, Pascal Francq wrote:
> > Hi,
> > I have develop an KDE application with a main window (inheriting
> > 'KXmlGuiWindow') containing one 'QMdiArea' widget. When multiple
windows
> > are opened, I want to give the user the opportunity too choose two
windows.
> > In practice, when clicking on a button in the toolbar, the user
clicks on
> > one window, holds the mouse button, move to the second window, and
release
> > the button. This works.
> > During the move, I want to draw a (red) line from the first window
to the
> > actual position of the mouse. The solution I use actually is to
catch the
> > movement of the mouse in the main KDE window, drawing a line in a
QPixmap
> > and calling 'updated()'. In the 'paintEvent' method of this KDE
window I
> > call the 'render' method of the 'QMdiArea' widget:
> >
> >       void KInfoMng::mouseMoveEvent(QMouseEvent* event)
> >       {
> >               if(Press)
> >               {
> >                       Pixmap=new QPixmap(Main->Desktop->size());
> >                       QPainter Painter(Pixmap);
> >                       Painter.setPen(Qt::red);
> >
Painter.drawLine(firstx,firsty,event->x(),event->y());
> >                       update();
> >               }
> >       }
> >
> >       void KInfoMng::paintEvent ( QPaintEvent * event )
> >       {
> >               if(Pixmap)
> >               {
> >                       Main->Desktop->render(Pixmap);  // The line
was draw
> in Pixmap
> >                       Pixmap=0;
> >               }
> >               else
> >                       KXmlGuiWindow::paintEvent(event);
> >       }
> >
> > But the QMdiArea does not show anything. Does this means that I have
to
> > create a class inheriting from QMdiArea and to overwrite the
'paintEvent'
> > method there?
> >
> > Thanks.
> 
> 
> - --
> 
> Pascal Francq
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