[Qt-interest] Dynamic painting in a QMdiArea

[Malyushytsky, Alex]

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

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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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