Re: Issue with QwtPlotRescaler

[Uwe R. <Uwe...@ti...>]

Hi Sebastien,

> I add some code in RectItem::draw() to illustrate this (see code
> below). It displays the ratio between the y scale and the x scale and
> then we can see that the ratio is exactly 1 only if the canvas is a
> square.

The main problem of the rescaler is the composite architecture of
QwtPlot. So the rescaler tries to adjust the scales according to
expectations what the layout code will do later.

I did a quick test with resizing the window of the example in Fixed mode
and for smaller windows I can observe that the error increases with an
increasing ratio for canvas.width() / canvas.height().

The worst size for the circle I had was for a canvas size of ~1000x200
that resulted in a "circle" of ~311x307. The difference between x_scale
and y_scale ( according to your code snippet ) goes above 0.1, what
indicates, that there is indeed a mismatch between what the rescaler
expects and what the layout is doing.

Please file a bug report, but as this is not a simple one it might take
some time until I will be able to work on it. If you want to do some
investigations on your own please let me know what you find out.

Uwe