scroll acceleration experiment

[willmcgugan]

Adds scroll acceleration, so the scroll position moves in greater increments when the wheel or trackpad is moved faster. Conversely slower motions move the scroll position slower, at a line at a time.

The feels better to me. Wheel and trackpad feel nearly right. But would like feedback...

But don't look at the implementation yet!

[davep]

The feels better to me. Wheel and trackpad feel nearly right. But would like feedback...

To mirror what I said on Slack: testing this here (macOS 13.2, 2019 MacBook Pro (Intel), iTerm, Magic Trackpad and a Logitech M575 trackball), I'm finding that this change:

• Makes trackpad movement very jumpy; whereas before scrolling has always been butter-smooth and precise, this feels very ragged and tricky to land where I want the scroll to land.
• Scroll wheel movement on the trackball seems to have massively slowed down with this change. I've not tested side-by-side yet but it feels slower than before Scroll sensitivity #1689