>Maybe the UI coordinate system is using floats and a rounding error aggregated over many days
It's using floats on 32bit (...which means only the watchOS currently, I guess?) and doubles elsewhere.
Are there any modern UI frameworks that _don't_ use floats/doubles?
I was gonna guess CSS, but even that has supported sub-pixel precisions on HiDPI displays for a while now.
[1]: https://stackoverflow.com/questions/5709698/html-sub-pixel-b...