I just merged this with master:
Basically, you can feed back the base brush size into any mypaint setting. There are many uses for this, the most obvious being to control hardness and pixel feathering so that your brush doesn’t disappear when it gets too small. A somewhat unexpected benefit is being able to make a brush where the dab size doesn’t really get much bigger, but instead more dabs are drawn-- effectively making a “high definition” brush that looks more or less the same even when scaled to very large sizes.
This can be a huge deal, because many brushes right now are basically designed for a particular resolution or zoom level (I know Deevad designed his brushes for 50% zoom). I think there are many candidate brushes that could benefit from this setting to make the brush scale bigger and smaller more consistently. I’ve been using this input for a lot of my brushes and found it to be a necessity.
Important to note, this is the “base” brush size, the one controlled with the slider and the key shortcuts. NOT the “actual” brush size that may or may not be controlled by other inputs like pressure.