1878876 - Autoscroll feature on tabs.ultimate-guitar.com fails

Status: NEW

(Core :: Panning and Zooming, defect, P3)

Description

[Dennis Schubert [:denschub]]

STR:

1. Go to https://tabs.ultimate-guitar.com/tab/fountains-of-wayne/stacys-mom-chords-58371
2. Click the "autoscroll" button

On macOS, Linux, and Windows 11 - this works fine. However, on Windows 10, according to this webcompat report and our own tests, it doesn't scroll.

We don't really know what's going on there, and building an isolated test case might be complicated. Filing it here in the hope you have an idea what might be happening here - but if not, we can try building a testcase for this.

Comment 1

[Hiroyuki Ikezoe (:hiro)]

It works on my Thinkpad T460p with Windows 10 Pro 22H2.

Comment 2

[Hiroyuki Ikezoe (:hiro)]

Oops, I was misunderstanding what "autoscroll" means. I just tried to use our autoscroll feature, rather than the one provided by the site.

Indeed, the "autoscroll" feature on the site stops working after a little bit scrolling. Anyways, if the scrolling provided by the site, which means it's likely scrolling by JS. It's unclear to me the issue is related to APZ or not.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:botond, could you have a look please?

For more information, please visit BugBot documentation.

Comment 4

[Dan Robertson (:dlrobertson)]

Could you by chance reproduce this and capture a profile with logging enabled?

about:logging?modules=apz.controller:5,apz.manager:5,apz.inputqueue:5,apz.inputstate:5,apz.activeelement:5,apz.eventstate:5&output=profiler

Should provide us with the necessary info.

Comment 5

[Dennis Schubert [:denschub]]

Forwarding the previous needinfo to James - I don't have a Windows 10 machine anymore, but he could reproduce this.

Comment 6

[James Graham [:jgraham]]

I can look later, but if hiro can reproduce it that might be the faster way to debug whether this is actually APZ related, since he's presumably already used to investigating those bugs :)

Comment 7

[Botond Ballo [:botond]]

(In reply to Dan Robertson (:dlrobertson) from comment #4)

Could you by chance reproduce this and capture a profile with logging enabled?

about:logging?modules=apz.controller:5,apz.manager:5,apz.inputqueue:5,apz.inputstate:5,apz.activeelement:5,apz.eventstate:5&output=profiler

Should provide us with the necessary info.

I got one: https://share.firefox.dev/4c6xdDk

In the profile I started and stopped the site's autoscroll feature twice; in between, I scrolled with the mouse wheel to a different starting position. The first time, the site's autoscroll feature did not scroll at all. The second time, it scrolled a small amount for a handful of frames and then stopped.

Comment 8

[Hiroyuki Ikezoe (:hiro)]

I tried to debug this on a Windows 10 on a VM, unfortunately this issue can't be reproducible on the VM for some reasons. So there's definitely something preventing scrolling not specific to Windows version. I used Windows 10 Pro 22H2 FWIW.

Comment 9

[Dan Robertson (:dlrobertson)]

Setting as S3/P3 since it is an intermittent failure, but going to add this to the diagnosis backlog.

Comment 10

[Hiroyuki Ikezoe (:hiro)]

Today I could reproduce this bug on my Windows 11 laptop. Also I could reproduce on my Linux desktop, but it's just once unfortunately.

And now I am suspecting this is something related to layout metrics in the site. On the windows 11 laptop, if I do full zoom to 120%, the autoscroll feature works, if it's 110%, it doesn't work.

Comment 11

[Hiroyuki Ikezoe (:hiro)]

               t => {
                  const {
                    current: e
                  }
                  = n;
                  if (!c.current || !s.current || !e) return;
                  const o = 0 < window.innerHeight - a - s.current.getBoundingClientRect().bottom,
                  i = e instanceof Window ? e.scrollX : e.scrollLeft;
                  if (o) {
                    if (!t) return void h();
                    e.scrollTo(i, 0)
                  }
                  if (!o) {
                    const t = e instanceof Window ? e.scrollY : e.scrollTop;
                    e.scrollTo(i, t + p.current)
                  }
                  const l = 1000 / d.current * (Zo.nR / (40 - (40 / 15 - 1)));
                  r.current = window.setTimeout(g, l)
                }
              ),

The scroll operation in question is probably the second scrollTo in above code snipet. It looks suspicious related to our scroll position rounding / pixel alignment issues.

Comment 12

[Hiroyuki Ikezoe (:hiro)]

On the Windows 11 laptop, the p.current value is fractional, it's 1.009765625. It's quite odd, Chrome on the same machine reports it 1. The value comes from window.outerWidth / window.innerWidth. I have totally no idea why these values are different on Windows.

Comment 13

[Hiroyuki Ikezoe (:hiro)]

Confirmed that setting layout.scroll.disable-pixel-alignment to true fixes this bug.