gmane.comp.graphics.qwt.general

clear zoom stack

Hi all,
is there a way to clear the zoom stack without forcing a replot?

I need to synchronize several QwtPlot objects. To do that I basically 
call a zoom(rect). But since the plots may also have an independent zoom 
I cannot live with the actual zoom stack during synchronization. That 
means I have to clear the previous zoom stack.

I found a workaround as follows but I would like to know if there is a 
better way to implement that.

derive MyPlot from QwtPlot
reimplement replot() virtual method and check for a flag. Call 
QwtPlot::replot() depending on that flag.
in the sync zoom method:
- set the flag to false to disable replot
- zoomer->zoom(0)
- set the flag to true to reset the default behaviour

Thanks for your help
Gianni

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Uwe Rathmann | 28 Apr 21:00

Re: clear zoom stack

On Monday 28 April 2008 13:34, Gianni Ambrosio wrote:

> I need to synchronize several QwtPlot objects. To do that I basically
> call a zoom(rect). But since the plots may also have an independent zoom
> I cannot live with the actual zoom stack during synchronization. That
> means I have to clear the previous zoom stack.

What about zoomer->setZoomBase(false); ?

> - zoomer->zoom(0)
> - set the flag to true to reset the default behaviour

The zoomer always uses QwtPlotZoomer::rescale() to change the axis scales. 
This should be a better place for such a flag.

Uwe

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