zoomer in spectrogram example

Hello,

I have noticed a strange behaviour in spectrogram example, namely if I set the data of spectrogramData class and data for QwtPlotCurves within the constructor of plot class, then the zoomer function is okay, but if I set the data outside the constructor, but from another class, which has got a pointer to the plot class, then I can zoom in, but not zoom out anymore. The right mouse click cause the grey background of plot and all my QwtPlotMarkers are at once in the left bottom corner of the plot.

Can you explain me why it happen like this and how to avoid it? Thank you.

best regards,

Vitali