QwtPlotPicker::getInvTransform does not map to correct plot coordinates

**hakiim35** · 16th May 2011, 13:46

Hello, I tried but it didnt give correct result. I guess, the value you subtracted is the zero point in pixel coordinates, but I want to get the zero point in plot coordinates..

**Uwe** · 16th May 2011, 16:55

Don't use a picker here - it's a QObject, that needs event processing - something, that is not happening the way you wrote your code.

Instead do something like this:

Qt Code:

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QPointF myCurveWidget::mapMousePoint(QPoint mousePoint)
{
   const double x = canvasMap( QwtPlot::xBottom ).invTransform( mousePoint.x() );
   const double y = canvasMap( QwtPlot::yLeft ).invTransform( mousePoint.y() );
 
   ...
}

QPointF myCurveWidget::mapMousePoint(QPoint mousePoint)
{
   const double x = canvasMap( QwtPlot::xBottom ).invTransform( mousePoint.x() );
   const double y = canvasMap( QwtPlot::yLeft ).invTransform( mousePoint.y() );

   ...
}

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I'm not 100% sure if this already solves your problem, but at least it's better than using a picker and it should be easier to find out what is going on. If the bug is still there you should check p1, p2, s1, s2 of the maps to see if there are pending updates of the scales because of a missing replot.

Uwe

**hakiim35** · 17th May 2011, 10:04

Hello, it didnt help either..but I will try to investigate it deeper..
By the way, isnt it possible to retrieve the width of the vertical ruler on the left part of the widget?