1917726 - Page unexpectedly shifts when trying to scroll subframe (with toolbar-on-top)

Status: NEW

(Fenix :: Browser Engine, defect)

Description

[Markus Stange [:mstange]]

Attachment: screen recording

Steps to reproduce:

1. Go to this bus timetable page, or any page which has a vertically-scrollable subframe on a vertically-scrollable page.
2. Scroll down the outer page until you see the subframe / the bus timetable. (This hides the dynamic toolbars.)
3. In the bus timetable, scroll down a little bit, and then scroll up a little bit.

Expected results:
The outer page should remain the way it was, only the subframe should be scrolled.

Actual results:
When scrolling up inside the subframe by just the tiniest amount, the toolbars reappear fully, and cause the entire page to shift down. This is very disorienting.

In the attached screen recording, I was reading the second row of the table, and wanted to scroll back up to the first row ("Westport Railway Station"). But the page shifted so that both row 1 and row 2 are now hidden!

Comment 1

[Petru-Mugurel Lingurar [:petru]]

Think this is assumed but wanted to confirm, this is happening because we get an inputResultDetail which says that the website handled the scroll.

Seems like a good ticket to add to the meta for tracking issues before moving to use scroll data to drive the dynamic toolbar - bug 1915640.
Though now I'm thinking that rather bug 1893221 should be blocking the new meta? That would be so meta! 😏

Comment 2

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

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

For more information, please visit BugBot documentation.

Comment 3

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

The Bugbug bot thinks this bug should belong to the 'Fenix::Toolbar' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 4

[Markus Stange [:mstange]]

There are two parts to this bug: the page unexpectedly shifting, and the toolbar unexpectedly appearing.
Bug 1921331 is expected to fix the first part. Bug 1914119 is expected to fix the second part.

Comment 5

[Markus Stange [:mstange]]

Attachment: captured page, for posterity