- Mark a method as `static`
- use `Math.sqrt` instead of `Math.pow(…, 0.5)`
- Use `Math.sign` instead of a condition on the sign
- Inline some used-once variables
- Reduce the scope of some variables
According to https://caniuse.com/?search=passive,
all browsers released after 2016 do support passive event listeners,
so no need to check for its presence.
When the touchmove listener is registered with passive: false, scrolling
up on Firefox Android only works every other attempt. When scrolling
breaks, the touchmove callback is never invoked.
The passive flag was originally set to false as part of a fix to prevent
vertical scrolling while swiping: 3f31744911.
Setting passive to true doesn't seem to negatively affect that in both
Firefox and Chrome, but fixes the scoll up behavior on Firefox.
Fixes: #2053
Signed-off-by: Andrew Gunnerson <accounts+github@chiller3.com>
