[Qt-interest] Dynamic painting in a QMdiArea

[Pascal Francq]

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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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