Vertical scrolling while in landscape orientation causes unintentional jumps

[kloberle]

Steps to reproduce

1. Open Firefox for iOS on an iPhone
2. Visit, for example, the article about Firefox in Wikipedia
3. Expand the Platform availability section to expose its tables (not a requirement)
4. Scroll to the bottom of the article
5. Turn phone to landscape orientation
6. Scroll several screen-heights up the article, then scroll down the page

Expected behavior

The page will scroll smoothly up&down in both portrait and landscape orientation

Actual behavior

In landscape orientation, scrolling will often cause the page to jump unexpectedly, often to the bottom of the page. Can make navigating around a wide table very difficult.

Device & build information

• Device: iPhone 13 Pro; iOS 17.4.1
• Build version: Firefox 125.3 (41348)
• First seen version: Noticed with older Firefox versions as long as the past year.

Notes

Does not appear to be an issue on iPadOS.

┆Issue is synchronized with this Jira Task

[data-sync-user]

➤ Nishant Bhasin commented:

FYI: Matt Reagan

[mattreaganmozilla]

@kloberle I haven't been able to replicate this yet, does it happen consistently for you? I do see the scroll indicator will jump slightly (but this is expected due to the toolbar being shown/hidden, which changes the scroll view size). I haven't been able to see the page jump to the bottom as described in the ticket, however. Can you please try attaching a video of what you're seeing?

[kloberle]

Done; one is taken in Firefox, the other in Safari.
I had subjectively believed this behaviour applied to multiple sites I visit, but in testing yesterday was only able to observe it for pages on Wikipedia -- so perhaps it's Wikipedia only?
I only use Firefox in Private Browsing mode, and had the considered it might scroll properly in regular mode...however, the attached Firefox video was recorded in regular mode.
Thanks.

[data-sync-user]

➤ Matt Reagan commented:

(Attaching video provided by reporter)

!FireFox.mp4|width=888,height=1920,alt="FireFox.mp4"!