1289645 - Scrolling horizontally in tab bar is not smooth on OSX with Apple Magic Mouse

Status: RESOLVED WORKSFORME

(Core :: Widget: Cocoa, defect, P4)

Description

[ipat500]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:47.0) Gecko/20100101 Firefox/47.0
Build ID: 20160604131506

Steps to reproduce:

- Use an Apple Magic Mouse
- Open lots of tabs, enough so they don't all fit in the tab bar.
- Hover the mouse cursor over the tab bar
- Scroll very fast (either horozontal or vertical) through the tabs. Just before the end of the bar give a little flick to give the scroll some momentum
- You may need to try this a few times to see the effect clearly


Actual results:

- Just before getting to the end the scrolling will bounce back a little. It keeps doing this by different amounts each refresh. It makes it look like it is constantly trying to go in the direction it is being told, but is straining against something until it slows down.
- The distance of the bounce back is a little less than the width of one tab, but varies
- As the mouse scroll momentum slows down the bounce-back gets smaller until it the speed gets below some threshhold and the scroll behaves normally again.
- After you see the effect the scroll will always eventually get to the end if you stop touching the mouse. So the bounce back doesn't cause the scroll to get stuck permanently, only for a second or so.
- It is possible to stay in the stuck state for quite some time by continually scrolling in the same direction to keep the scroll momentum going.
- This effect does not happen if the scroll is not given a flick (giving it momentum), and does not happen if the momentum is small, only big flicks cause this effect.

I suspect what is happening is that firefox is misinterpreting the very high scroll delta's it gets from the mouse and applying them in reverse if they hit the end.

A seemingly related effect happens when not near the end of the scroll space. If momentum is extremely high scrolling seems slightly slower than if the scroll speed is slower. Although this is not as pronounced as the effect at the ends of the scroll space.

These effects only seems to happen in the tab bar, not in the page itself.


Expected results:

Tab scrolling should continue only in the direction dictated by the mouse, and only stop when they get to the end, or the mouse stops scrolling.

Comment 1

[ipat500]

This seems fixed in 48.0.1
Can this ticket be closed now?

Comment 2

[Jim Mathies [:jimm]]

thanks for reporting!