Adjust brush cursor size according to pressure
In Krita, the brush cursor shows the actual radius of the brush as applied to the canvas AFTER applying all modifiers. In Drawpile, the radius appears to be restricted to the brush size parameter, and does not consider the effect of tablet pressure, velocity, or distance.
(I've taken over development on Drawpile, so I'm going through these tickets and organizing them.)
This could be implemented for classic brushes, but wouldn't really work for MyPaint brushes, which are coming with Drawpile 2.2. Krita doesn't support the brush cursor with changing size for those either. So I'm inclined to say it ain't worth it to implement the circle jigger if it's not applicable to an entire class of brushes.