[PyQwt] Drawing a curve with QwtPlotPicker

[banshee.beats]

Hello everyone,

i'm trying to let the user draw a curve on my plot canvas, to emit a signal after releasing the mouse and send the array of points to another method for further processing.

Right now my code looks like this:

(...)
      self.plotPicker = Qwt.QwtPlotPicker(Qwt.QwtPlot.xBottom, Qwt.QwtPlot.yLeft, Qwt.QwtPicker.PolygonSelection, Qwt.QwtPlotPicker.PolygonRubberBand, Qwt.QwtPicker.AlwaysOn, plot.canvas()) 
      self.plotPicker.setRubberBandPen(QPen(Qt.green))
      self.plotPicker.setTrackerPen(QPen(Qt.cyan))
      self.connect(self.plotPicker, SIGNAL('selected(const QwtArrayQwtDoublePoint &)'), self.onSelection)
 
 
def onSelection(self, points):
      print 'i got triggered'

(...)
      self.plotPicker = Qwt.QwtPlotPicker(Qwt.QwtPlot.xBottom, Qwt.QwtPlot.yLeft, Qwt.QwtPicker.PolygonSelection, Qwt.QwtPlotPicker.PolygonRubberBand, Qwt.QwtPicker.AlwaysOn, plot.canvas()) 
      self.plotPicker.setRubberBandPen(QPen(Qt.green))
      self.plotPicker.setTrackerPen(QPen(Qt.cyan))
      self.connect(self.plotPicker, SIGNAL('selected(const QwtArrayQwtDoublePoint &)'), self.onSelection)


def onSelection(self, points):
      print 'i got triggered'

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This does not work, the method does not get triggered. If i replace QwtPicker.PolygonSelection with QwtPicker.PointSelection and change the SIGNAL accordingly it works just fine.

Where am i going wrong here? Thanks a lot in advance!