QwtPlot/Canvas and QPainter

[carhun]

Hello.

How can i get painter of QwtPlot, QwtPlotCanvas?

I try to do like:
QLine line(pos.x() - 5, canvas()->rect().bottom(), pos.x() - 5, canvas()->rect().top());
1st method:
QPainter *painter = new QPainter(const_cast<QwtPlotCanvas *>(canvas()));
painter->save();
painter->setPen(Qt::blue);
painter->drawLine(line);
painter->restore();

2d method:
QPainter *p = plot()->paintEngine()->painter();
p->drawLine(line);

3d method:
// canvas()->paintEngine()->drawLines(&line, 1);
QPaintEngine *pe = canvas()->paintEngine();
pe->drawLines(&line, 1);

There is no one work. Why?

And how than I need to draw some line (not QwtPlotCurve) at QwtPlot?

[Spitfire]

Just create a simple widget with trasnaprent background, stick it over the canvas and reimplement its paint() method.