QwtPlotZoomer zooming off the plot canvas

[BettaUseYoNikes]

I am using QwtPlotZoomer with a few graphs in my application but I am having a few problems. I do not want to allow the user to zoom off of the original canvas that is shown with the Plot on it, ie; zooming in to negatives.

[Uwe]

class YourZoomer: public QwtPlotZoomer
{
....

virtual void zoom( const QRectF &rect )
{
QwtPlotZoomer::zoom( rect & zoomBase() );
}
};
Uwe