Any ways to smoothly scroll with keyboard shortcuts?

[Oneechan69]

I realize that I have to keep taking one of my hands off the keyboard to scroll with the trackpad, and looked for ways to do so with the keyboard but none of them work the way I want them to. I could do FN Up Arrow and FN Down Arrow but those go up and down a "whole page" and that's too fast, I can't change how fast it goes. Its possible to make a Karabiner Elements config to scroll with shortcuts but they can't scroll smoothly (have scroll intertia, which is enabled in macOS Settings > Accessibility > Pointer Control > Trackpad Options > Use intertia when scrolling).

 

[f54da]

how exactly should inertial scrolling work when there is a fixed key repeat rate, unlike scrolling where the interval between scroll events determines how fast you are scrolling?

 

[Oneechan69]

Inertia scrolling works no matter how far you scroll on the trackpad, its accelerating when it starts and decelerating when it ends.

 

[f54da]

??? scroll inertia on the trackpad is clearly dependent on the velocity at which you scroll before stopping... that's why it's called acceleration in the first place. So when you simulate it with a keyboard either you hardcode a fixed acceleration or do something like use total keypress time as proxy for the inertia curve to use. Both are terrible solutions that will provide non-intuitive results.

What you actually want is not to apply inertia, but rather to simply scale the scroll velocity by elapsed keydown time. This gives you behavior that the scroll will accelerate faster the longer you hold the key. The moment you release the key, scrolling will stop though, because no inertia is in place.

 

[Ben J.]

Space bar:
Shifts page 100%.
Up/down-arrow press:
Shifts page ca. 20% of page.
Up/down-arrow press and hold:
Shifts page ca. 20% of page once, then scrolls fairly smoothly, but too quick to read everything.
(unless a curser is inserted in text, of course, as the arrows are preserved for the cursor)
Add cmd key:
Much quicker scroll

Alt-arrow in PDFs = next page.

Works in most apps like browsers, text editors, etc.