1917945 - With toolbar-on-top, scrolling a horizontal subframe can cause limited scrolling of the outer page

Status: NEW

(Fenix :: Toolbar, defect, P3)

Description

[Markus Stange [:mstange]]

Attachment: screen recording

Steps to reproduce:

1. Go to https://github.com/PlatformLab/NanoLog?tab=readme-ov-file or to any other vertically-scrollable page which has horizontally-scrollable subframes.
2. Scroll down until you see the subframe. Scrolling down hides the dynamic toolbar.
3. Horizontally scroll the subframe, first to the right and then back to the left, moving your finger slightly diagonally downwards as you get to the end of the scroll gesture.
4. Notice that the vertical motion of your finger caused the outer page to move vertically. Move your finger some more to cause more scrolling.
5. Notice that the unexpected vertical scrolling is confined to a small delta.

Expected results:
When the gesture is scrolling a subframe, the outer page should not move. The dynamic toolbar should not appear during a gesture that scrolls a nested scroll frame.

Actual results:
The dynamic toolbar causes the outer page to shift, giving the impression of broken scrolling because the vertical scrolling is confined within a small cage.

This bug is pretty similar to bug 1917726, with the difference that in this bug, the finger is still in control of the outer page movement, whereas in bug 1917726 the toolbar just appears fully at the tiniest scroll-up and will not hide again during the scroll gesture.

Comment 1

[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 2

[Markus Stange [:mstange]]

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

Comment 3

[Chris Peterson [:cpeterson]]

Petru, is this bug a regression from recent dynamic toolbar changes?

Comment 4

[Petru-Mugurel Lingurar [:petru]]

(In reply to Chris Peterson [:cpeterson] from comment #3)

Petru, is this bug a regression from recent dynamic toolbar changes?

Thanks for the ping!
Don't think it's a new regression as we didn't really touched the dynamic behaviour recently.
This seems like an old issue, a shortcoming of our current approach that is to be solved with the transition to a new framework for animating the toolbar.
Seems like Markus already set the right dependencies, thanks!
It's good to know of these buggy scenarios and use them as a reason for developing the new framework and then as a way to validate the improvements.