Repainting a QGraphicsView

[Luc4]

Hi! Is it possible to redraw a QGraphicsView so that, in case it has the focus, it has a border around? I tried to paint it like any other widget, overriding the paintEvent method, but it seems nothing happens. Is there any other way?
Thanks for any advice!

[jpn]

Could you show the relevant code, please? Did you remember to open the painter on the viewport as instructed in QAbstractScrollArea:aintEvent() docs?

[Luc4]

mmh... in the doc I found that the paintEvent method is reimplemented from QWidget:aintEvent(...). So, I did what I usually do with QWidgets.

QPainter painter;
painter.setBrush(QBrush(Qt::gray));
painter.drawRect(QRect(0, 0, this->width(), this->height()));

QPainter painter;
painter.setBrush(QBrush(Qt::gray));
painter.drawRect(QRect(0, 0, this->width(), this->height()));

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Then, I painted the scene, ad I saw this cannot be omitted:

QGraphicsView::paintEvent(event);

QGraphicsView::paintEvent(event);

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What do you mean by "open the painter"? It seems I'm lacking something...
Thanks for your answer!

[gopikrishnav]

Hi Can you please let me know where you are trying to draw the border? On Scene or View?

[aamer4yu]

Show us the paintEvent of your view class.
Probably you are first painting the border and then calling the base class paintEvent. This will override your painting !
You will need to first call the base class function and then draw after it.

[Luc4]

This is what I wrote:

void MyView::paintEvent(QPaintEvent* event) {
   QGraphicsView::paintEvent(event);
   QPainter painter(this);
   painter.setBrush(QBrush(Qt::green));
   painter.drawRect(QRect(0, 0, this->width(), this->height()));
}

void MyView::paintEvent(QPaintEvent* event) {
   QGraphicsView::paintEvent(event);
   QPainter painter(this);
   painter.setBrush(QBrush(Qt::green));
   painter.drawRect(QRect(0, 0, this->width(), this->height()));
}

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I can't understand. Maybe some other property I don't remember inserting is overwriting the background...

EDIT: I noticed in debug mode I get this:
warning: QPainter::begin: Paint device returned engine == 0, type: 1
warning: QPainter::setBrush: Painter not active
warning: QPainter::drawRects: Painter not active

[totem]

try this :

void MyView::paintEvent(QPaintEvent * e)
{
	// 1. draw scene items
    QGraphicsView::paintEvent(e);
 
    // 2. draw zoom area if any
    if( m_zoomArea.width()!=0 || m_zoomArea.height()!=0 )
    {
	QPainter painter( viewport() );
        painter.save() ;
        // paint here
        painter.restore() ;
    }
}

void MyView::paintEvent(QPaintEvent * e)
{
	// 1. draw scene items
    QGraphicsView::paintEvent(e);

    // 2. draw zoom area if any
    if( m_zoomArea.width()!=0 || m_zoomArea.height()!=0 )
    {
	QPainter painter( viewport() );
        painter.save() ;
        // paint here
        painter.restore() ;
    }
}

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i.e., draw on view's viewport instead

[Luc4]

It seems it is not redrawing correctly the scene, lines remain in the area. This is what I wrote:

void MyView::paintEvent(QPaintEvent* event) {
   QGraphicsView::paintEvent(event);
   QPainter painter(this->viewport());
   painter.save();
   QPen pen;
   pen.setColor(SELECTION_BORDER_AREA_QCOLOR);
   pen.setWidth(GoodiesStore::SELECTION_BORDER_AREA_WIDTH);
   painter.setPen(pen);
   painter.drawRect(QRect(0, 0, this->width(), this->height()));
   painter.restore();
}

void MyView::paintEvent(QPaintEvent* event) {
   QGraphicsView::paintEvent(event);
   QPainter painter(this->viewport());
   painter.save();
   QPen pen;
   pen.setColor(SELECTION_BORDER_AREA_QCOLOR);
   pen.setWidth(GoodiesStore::SELECTION_BORDER_AREA_WIDTH);
   painter.setPen(pen);
   painter.drawRect(QRect(0, 0, this->width(), this->height()));
   painter.restore();
}

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When I scroll the view, it seems lines are scrolled too.
Thank you for your help!

[Luc4]

In case anyone else need this, I didn't know how to solve this so I placed a label under the QGraphicsView and made it larger than the QGraphicsView. The result is exactly the same.