Created attachment 134867 [details] px repeated infinitely couldn't delete SUMMARY STEPS TO REPRODUCE not sure OBSERVED RESULT in gif EXPECTED RESULT to be able to delete the unit SOFTWARE/OS VERSIONS Windows: 10 macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION I also found the UI for the circle select tool completely counter intuitive. When I click those lock symbols I fully expect them to unlock. In addiction when I increase or otherwise rewrite the values for the size I expect the circle on the screen that I just put down to change size not for the circle I will put down to change size. But I can see that being an intentional design choice considering you can accumulate selections to which the size could not apply.
Yes, I see the gif... But the code that manages the spinbox's unit suffix is in QSpinBox, so this would be a bug in Qt. As for your other remarks, I do agree with them. The problem is that if you use the tool on a paint layer, there is no circle before you create one, but there also isn't a circle after you have created the tool: it directly changes pixels, but doesn't put a circle object somewhere, so there's nothing that could be changed. This is something we want to refactor, because for all raster tools it would be nice if the last stroke could be modified before baking it in the paint layer. I'll rename this report accordingly and change the status to wish.