RE: Syncing several QwtPlotPickers

[David S. <david_stranz@MassSpec.com>]

Ewald,

The implementation of QwtPlotPicker makes it hard to do this
without getting into infinite recursion with moved() signals.

I would do this:

- create a class (QPickerManager) whose job is to listen for the
moved(), selected(), etc. signals from plotpickers and to update
other plotpickers.  This class keeps a list of the linked pickers
and has methods to add / remove them from the list.

- subclass QwtPlotPicker and create new methods: moveAux(), selectAux(),
etc. 
so that do the same thing as move(), select(), etc. to update the picker 
state but -do not- emit the moved(), selected(), etc. signals.  Copy
the code in QwtPicker::move() (qwt_picker.cpp, line 1235) for example,
but leave out the "emit moved()" line.  This is how you avoid recursion.

- when a picker is added to QwtPickerManager, connect the 
QwtPlotPicker::moved() signal to QwtPickerManager::onMove(), etc.

- when a plotpicker fires its moved signal, QwtPickerManager iterates
over its list of plotpickers and calls their moveAux() methods.  
(This will result in the state being updated twice for the picker who
fired the original signal - maybe you can check the isActive flag
and ignore the update if the flag is set, or maybe you need your
own flag in the subclassed QwtPlotPicker you make.  I don't know if
updating the state twice has side effects - it probably does for
methods like append(), so you want to avoid that).

I think this will do what you want.  Remember that there is only one
cursor, so any display in the linked plots will not include the
cursor, only the highlighting or whatever other visual display
there is for the picker style you have chosen.

Let us know if this works.

Regards,

David

_______________________________________________________________
David Stranz, Ph.D.	david_stranz@MassSpec.com

Sierra Analytics, Inc.
5815 Stoddard Road, Suite 601
Modesto, CA  95356

Tel: (209) 545-8508
http://www.massspec.com
_______________________________________________________________
 
 

> -----Original Message-----
> From: qwt...@li... 
> [mailto:qwt...@li...] On Behalf 
> Of Ewald de Wit
> Sent: Saturday, June 21, 2008 10:34 AM
> To: List for both Qwt users and developers
> Subject: Syncing several QwtPlotPickers
> 
> Hi,
> 
> I have several plots, each with their own plotpicker. What I 
> would like
> is that if one plotpicker becomes active and starts moving, the other 
> plotpickers start to visually move in sync with it.
> 
> Is this possible?
> 
> --
>   --  Ewald
> 
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