Created attachment 133711 [details] you see a little square that is missing in the subtract selection mask (=red), and when i want to subtract it, it randomly fills the whole mask, except the part i want to subtract SUMMARY STEPS TO REPRODUCE 1. on new layer select rectangular selection tool 2. select subtract 3. make pattern you want to be cutout from layer below OBSERVED RESULT sometimes it adds instead of subtracting and vice versa EXPECTED RESULT not doing that? SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION
I believe that the operation of the selection tools in Subtract mode are logically/arithmetically correct but it can be confusing. Also, there's a subtle difference if you use the global selection mask instead of relying on the 'marching ants' outlines. Please go to https://krita-artists.org/ and start a topic there in the Support and Advice: General Questions category. That forum is a very suitable place for discussion and posting many illustrative images as part of the discussion.
Yes, this seems to be a confusion about what the mask actually does. It represents the unselected areas with overlay, and selected areas without an overlay, so subtract will add overlay. This is how it works in all programs with such a mask, so I will close this bug.