Circle detector to render roundabouts and building parts smootly

And: Yes!: circular ways are softened now.
“circular detection” was easy: the radius of all nodes must be about equal, maximal 10 % differences at the moment. And at last 10 nodes, to be a circle. How does it look, compared with the first version above?

That will not always fit. The limits will become parameters of the lib. So you even could switch of options like this.

Look at that part, the arrow is pointing to. No soft corners. It is cyclic with 4 squares on each side. But as it is tagged as one single way. It is not detectable as circular. That could be edited to refine the building. Not for the renderer! That part is a compromise anyway, to have not to much detail tagging.

Try it. find the way of a building, you like to check, put the way-id in the url, like this:
https://www.osmgo.org/bevy.html?way=109862851

Is your building is correctly rendered and edged?