Updating and Zooming Plot, that is frequently filled with new Data

[entonjackson]

Hello Qt and Qwt Folks!

This is my 1st post. Sorry if this topic was already handled here in the forum, but i have found nothing.
My English is not perfect, sorry for that.

Let's get to my topic...
My problem is, that i want to plot a curve, that is updated with data from the database every 500ms. In the past i did this by doing setSamples(x_vals, y_vals); and after that replot(); inside my class that inherits QwtPlot.
That worked fine, but now I also want to zoom. Zooming in by rubberband and mousewheel, zooming out by right-clicking. So i implemented a QwtPlotZoomer and installed to my QwtPlot.
And it works fine... as long as you don't update the Plot! It zooms in for a tiny piece of a second and then immediatley zooms out again, after replot() is called.

So, my idea was to just add data to my plot and let it handle update and zooming functionality itself.
But I'm just not getting it, how to do that... i tried setAutoReplot(true); ... same problem as before.

I hope someone can help me. I'm stuck for days, trying out stuff from the qwt examples. trying out setting any scales or scaledraws or scaledivs. This cannot be that difficult, can it?


Thanks in advance!