1701699 - Axis locking does not lock the overscroll starting velocity - On pages where both axes are scrollable, vertical scrolling can cause a diagonal overscroll bounce

Status: NEW

(Core :: Panning and Zooming, defect, P2)

Description

[Markus Stange [:mstange]]

Attachment: screen recording

This is similar to bug 1701077, but not fixed by the patches in it.

Steps to reproduce:

1. Be on macOS and have apz.overscroll.enabled set to true.
2. Go to page that is scrollable both vertically and horizontally, for example https://planet.mozilla.org/ .
3. Scroll down a bit.
4. Do a fling to the top, slightly diagonally to the top left, in an 11 o'clock direction. This is vertical enough that axis locking will turn it into a vertical scroll with no horizontal overscroll.

Expected results:
The overscroll bounce at the end of the scroll should be vertical.

Actual results:
The overscroll bounce is diagonal. See the attached screen recording.

My guess would be that the problem is that axis locking does not affect the axis velocity. I think it should.

Comment 1

[Botond Ballo [:botond]]

Agreed, I don't think it should be difficult to make the velocity passed to the overscroll animation respect axis locking.

Comment 2

[Botond Ballo [:botond]]

Dropping as release blocker per discussion with Martin.

Comment 3

[Hiroyuki Ikezoe (:hiro)]

I believe Dan's dominant axis locking solved this bug on Mac. I am going to change this bug specific for Windows tentatively. That's said, as I tested on Edge, overscrolling is diagonal there, so maybe we will consider this bug as WONTFIX or some such.

Comment 4

[Hiroyuki Ikezoe (:hiro)]

Okay, I test this again both on Windows and Mac.

(In reply to Markus Stange [:mstange] (PTO until Sep 7) from comment #0)

Steps to reproduce:

1. Be on macOS and have apz.overscroll.enabled set to true.
2. Go to page that is scrollable both vertically and horizontally, for example https://planet.mozilla.org/ .
3. Scroll down a bit.
4. Do a fling to the top, slightly diagonally to the top left, in an 11 o'clock direction. This is vertical enough that axis locking will turn it into a vertical scroll with no horizontal overscroll.

If I did lift my fingers from the touchpad in between 3 and 4, and did the fling at around 45 deg up-leftward, I still see the diagonal overscrolling both on Mac and Windows. Is it the same issue originally reported?

Anyways, the current Firefox behavior matches what Edge does on Windows, so I am going to unblock overscroll-windows now.