1690849 - If cursor is over tabs area when tabs aren't overflowing, scrolling horizontally shouldn't trigger page-back/forward

Status: RESOLVED FIXED

(Firefox :: Tabbed Browser, enhancement)

Description

[schneidro]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:84.0) Gecko/20100101 Firefox/84.0

Steps to reproduce:

Open enough tabs to make them overflow your screen width.
On the current tab, browse a few pages so that the back and forward buttons are enabled.
Place cursor anywhere over tabs area and then scroll left and right horizontally (two finger swipe on trackpad).
As expected, open tabs are scrolled left and right accordingly. NOTE: After reaching the first or last tab (maximum left or maximum right), nothing happens (as expected).
Now, close enough tabs until they are no longer overflowing.
On the current tab, browse a few pages so that the back and forward buttons are enabled.
Again place cursor anywhere over tabs area and then scroll left and right horizontally (two finger swipe on trackpad).
The horizontal scroll action now initiates page-back and page-forward.

Actual results:

The horizontal scroll action initiated page-back and page-forward when tabs were not overflowing.

Expected results:

Scrolling horizontally in the tab area should result in no actions when tabs are not overflowing. The behavior should be the same as if you reached the beginning or the end of the tabs when in overflow mode (which is to have no action). The current behavior of page-back and page-forward is unexpected and extremely frustrating (work can be lost sometimes).

The current behavior is exacerbated by the fact that if you have one less tab open than would overflow the tabs section, the tabs are very similarly compressed (visually) as they are when tabs are overflowing. Also, there seems to be an elastic number of tabs that enable overflow -- opening one tab will enable overflow, but it may require closing three tabs before overflow is disabled again. All of this is to say that when working near the overflow threshold, it's difficult to notice at a glance whether tabs have entered or left overflow mode, so it feels that much more unexpected when the current page navigates forward or backward.

Comment 1

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

The Bugbug bot thinks this bug should belong to the 'Core::Panning and Zooming' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 2

[Markus Stange [:mstange]]

I agree, scrolling in the browser chrome (or in the sidebar, for that matter) shouldn't cause back/forward swiping.

Comment 3

[Markus Stange [:mstange]]

Attachment: Bug 1690849 - Only trigger back/forward swipes when the mouse is over the content area. r=dao

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3ad6dc801e90
Only trigger back/forward swipes when the mouse is over the content area. r=dao

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/3ad6dc801e90

Comment 6

[Dão Gottwald [:dao]]

Attachment: Bug 1690849 - Remove obsolete comment.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/95ca7451cb96
Remove obsolete comment. r=mstange DONTBUILD

Comment 8

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/95ca7451cb96