Inset contour – no perfect circle in counter. Possible to change interpolation?!

Hi, I am new to glyphs.
I am trying to use the contours for a geometric font and I need to draw a perfect circle. However, when I set the contour to inset or center, there is no perfect circle in the counter but it gets squished. I do get a perfect circle when I set the contour to outset – but this is extremely unpractical since I want to be able to change the contour width quickly without having to resize the glyph.
Is there a way to change how this is interpolated? I don’t know python yet but I do know programming languages (php + javascript), so if it has to be a script, I am willing to dig into that as well. But maybe – finger crossed – there might be an easy setting that I missed somewhere?

Thanks for any hint regarding this!

The algorithm compensates the curvature for the inset. If you want the exact same curvature, better duplicate the shape and scale it down.

hmm… okay, thanks Rainer, maybe you could take that as a feature request to turn the compensation off? It’s a great idea to have that but in some occasions (like mine right now creating a geometric typeface) it’s in the way.


Can you please try the latest cutting edge version. It is fixed there (for some time already).