Showing small axis legend in QwtPlot

[ahisham]

Hi all,

I would like to show a small arrows pointing to +ve x and y directions inside the Qwt plotting area. I am already using Qwt axis with scales on them without any problem. Just for usability, it will be very useful to have a 90-degree small arrows corresponding to +ve x and y directions. This would be static at a corner of the plotting area and shouldn't pan or zoom with the plot.

What would be the appropriate way for drawing this ?

Thanks

[Cah]

subclass QwtPlotItem and re-define draw()

Something like this ...




class RefArrow: public QwtPlotItem
{
public:
explicit RefArrow(){}
virtual ~RefArrow(){}

void draw( QPainter *painter, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect ) const
{
QLineF vline(20, canvasRect.height()-20, 20, canvasRect.height()-80);
QLineF hline(20, canvasRect.height()-20, 100, canvasRect.height()-20);
painter->save();
QPen p(Qt::red, 3);
painter->setPen(p);
painter->drawLine(vline);
painter->drawLine(hline);
painter->restore();
}
};

Then ...



....

RefArrow * refArrow = new RefArrow;
refArrow->attach(plot);
...


This should give lines at 90 degrees and parallel to the axes.
It should be easy to add arrows

The stockchart example shows how one can implement there own PlotItems

[ahisham]

Perfect .. Exactly what I am looking for :)

Thanks