[MC-123773] Scrolling the hotbar on mac behaves weirdly starting in 18w01a

Mod Notice

In 1.14 (starting in Pre-Release 2)

In Mouse Settings, toggle "Discrete Scrolling" and set the sensitivity back to 1.

In 1.13 (starting in 18w21a)

Adjust the new mouseWheelSensitivity option that has been added to .minecraft/options.txt. In most cases, setting this to 10 will produce a reasonable hotbar behavior.

18w01a changed how scrolling works. Trying to scroll through hotbar slots is often unsuccessful now. Scrolling in the creative inventory is now very fine-grained, to the extent that it is now possible to change item lines without changing the position of the slider, see attached screenshots.

Scrolling, as observed in the creative menu, doesn't scale linearly with physical scrolling speed either.

I also attached a forced crash report for system info.

Note that this is different from ~~MC-122641~~, which was introduced in an earlier snapshot.

Likely caused by the fix for ~~MC-122053~~.

From the comments:

I have been doing some more testing on this issue. My setup is on MacOS 10.13.3 and a Logitech MX Master Mouse with the mouse wheel in "click-to-click" mode (i.e. you can move the mouse wheel one "notch" at a time with feedback.)

Prior to 18w01a, if you were to move the mouse wheel one notch on the hotbar, the selector would move across one slot for each notch.

Since 18w01a, it takes 10 individual notches to register the mouse moving across (it will move over on the 10th notch.) I have tested this by counting the number of individual notched scrolls before the selector will move across to the next slot in the hotbar. This effect happens in either direction.

Analysis

See this comment and this longer write-up.