[Interest] Handling zooming in QtCharts

[Jason H]

Having sued QtCharts in the past, I can say they are rather poorly implemented. I was able to get the charts on the screen but stuff was constantly ilided text.

Anyway, to do what you need, you probably have to render() it at a higher DPI than needed into an image then zoom in on the image. It's not great but it will work.






> Sent: Monday, June 20, 2016 at 5:54 PM
> From: "Lorne Sturtevant" <dragor at shaw.ca>
> To: interest <interest at qt-project.org>
> Subject: [Interest] Handling zooming in QtCharts
>
> I have been using QtCharts and so far it's going ok.  I can create basic
> charts without problems.  I am noticing some holes in the API which I
> imagine is just due to the fact that it's new.
> 
> One big problem I'm having is with zooming.  The functions
> QChart::zoomIn() and QChart::zoomOut() only allow zooming from the
> center of the chart.  I use the mouse wheel to zoom and I would like
> that to be done at the mouse's position.  So far, I cannot find a way to
> do this.
> 
> My first idea was to subclass QChart and just add a function to do it
> myself.  The problem with this, is that all the data I need to calculate
> the zoom point is in QChartPrivate, so that won't work.  I also thought
> about changing the range of the axis based on where the mouse is, but I
> can't see a way of getting the location of the grid lines to do an
> accurate calculation.  All the data I need is again private.
> 
> So my question is, how would I do this?  How can I zoom the chart around
> the position of the mouse without accessing any of the private data from
> the QtChart package?  Is there some method I'm missing?  Or is the API
> just not able to do this right now?
> 
> -- 
> Lorne Sturtevant
> Sum Ergo Cogito
> 
> _______________________________________________
> Interest mailing list
> Interest at qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest
>