Hi Uwe, I have a rescale copied from the QwtPlotMagnifier class in place. My implementation for ZoomIn and ZoomOut are as follows. My intention was to keep a scale factor, and basically change by 10% for zoom in/out. What I am noticing in practice with this approach, is that the zoom does not behave as I would expect. For example, if I zoom in 4 times, and zoom out 4 times, I am not often back to where I begin. This is exclusive of the zoom rectangle implementation. Perhaps this approach is not the best. Any thoughts on improving this approach?

Qt Code: 
  1. void Plot::zoomIn()
  2. {
  3.     m_scaleFactor -= .1;
  4.     if (m_scaleFactor < 0)
  5.         m_scaleFactor = 0;
  6.  
  7.     rescale(m_scaleFactor);
  8. }
  9.  
  10. void Plot::zoomOut()
  11. {
  12.     m_scaleFactor += .1;
  13.     //if (m_scaleFactor > 1.0)
  14.     //    m_scaleFactor = 1.0;
  15.  
  16.     rescale(m_scaleFactor);
  17. }
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