Ages ago, in my own editor (and missing HP chipmunk physical "paddle wheel" scrolling), I implemented the following mouse scrolling scheme:

    - Integrate the area* enclosed by recent mouse movement
    - Ignore everything under a threshold (this is normal, straight-line, mousing)
    - Scroll according to the sign of the area.
        . naively this would be slow scroll for small circles; fast for large
        . but I found it more intuitive to reverse the action:
            the bigger the gesture, the more controlled the scroll
            (probably closer to scroll-by-radian than scroll-by-area)

It looks like I could use this package to do something similar, only system-wide and portably, but I mention it here as it's the sort of project I'm extremely unlikely to Get Around To (and would therefore be chuffed if someone else were to!)

* https://en.wikipedia.org/wiki/Planimeter