With picker->setDisplayMode(QwtPicker::AlwaysOn) the positions is always displayed.

If you want to see that the QwtPlotPicker::moved() signal is emitted - even when the mouse is not pressed - there are many different ways to do it. Probably the most easiest one is to overload QwtPlotPicker::widgetMouseMoveEvent this way:

Qt Code:
  1. YourPicker::widgetMouseMoveEvent(QMouseEvent *me)
  2. {
  3. QwtPlotPicker::widgetMouseMoveEvent(me);
  4. emit moved(invTransform(me->pos));
  5. }
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HTH,
Uwe