Script area scrolling is very slow in Firefox

[towerofnix]

Expected Behavior

Scrolling with the scroll wheel happens at the same speed as in the block palette.

Actual Behavior

Scrolling is much slower.

Steps to Reproduce

Add a block to the scripting area so that the scrolling speed is clear, then use the scroll wheel to scroll.

Operating System and Browser

Firefox 57.0 on Debian (Testing).

[towerofnix]

It should be noted that scrolling is generally captured very slowly on Firefox, in terms of Scratch 3.0 - for example, panning the paint editor with the scrollwheel is very slow, as is zooming in and out (in both the paint editor and scratch-blocks).

[paulkaplan]

Ugh, it probably has something to do with this: https://developer.mozilla.org/en-US/docs/Web/API/WheelEvent/deltaMode

Firefox is the only browser that for some reason still uses line mode instead of pixel mode, and so all scrolling has to be checked against the delta mode. :(

[towerofnix]

Relatedly, on Firefox on a MacBook, trackpad scrolling is extremely fast in the palette. So the block palette has a separate but similar issue. (Perhaps there's code to make the palette scroll faster when on Firefox, but on a MacBook+trackpad that faster scrolling is not necessary?)