Add QwtPicker::trackerPositionChanged signal
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#67 Add QwtPicker::trackerPositionChanged signal
None
wont-fix
nobody
None
5
2020-03-01
2019-05-23
Anonymous
No
The patches attached to this ticket add a signal that fires whenever tracker position changes in QwtPicker. This functionality is needed when implementing synchronized plots with an overlay that is synchronized across all plots. We can connect to this signal of all 'subplots' and redraw the overlays whenever tracker position changes. Additionally, this allows implementing a secondary UI (or plot) that shows additional information specific to the point that the user is howering onto.
There are two attached patches - one for qwt-6.1 branch and one for trunk.
Discussion
Anonymous
Patch for qwt-6.1 branch
A patch for trunk.
Not sure about this patch. As it is done in widget not plot coordinates, it looks a lot like you are interested in tracking mouse movements - not in the position of the tracker.
What exactly is your use case ?
The use case is to draw an overlay across multiple widgets at the tracker position. This is possible to do outside Qwt, but all the logic would need to be duplicated to match the behavior of Qwt trackers, so I think the best place for that code is Qwt itself.
When installing an event filter for mouse events on the plot canvas - what logic has to be implemented in your code, that you don't need to do when connecting to the tracker position ?