2027230 - Testcase generating N chained containers and autoscrolling them blocks the UI (compositor thread) for 8s-10s.

Status: NEW

(Core :: Layout: Scrolling and Overflow, defect, P3)

Description

[Mayank Bansal]

Attachment: nested Scroll to.html

This is on Windows.

STR:

1. Open testcase
2. Click build
3. Click run
4. Once the run is complete, click inside the container and try to scroll too.

AR: UI is blocked for multiple seconds. The scrollbars also appear to be weirdly black.
ER: Not so?

https://share.firefox.dev/4s0MDzB, https://share.firefox.dev/4db4WOV

With the "always show scrollbars" in Windows accessibility, the scrollbars atleast appear normally. The page is still slow though.
Chrome is much better here.

Comment 1

[Mayank Bansal]

Different STR:
Reduce the nesting depth to lets say 10. Increase the iterations to 50000. Click Build and Run
Profile: https://share.firefox.dev/4db515b

Comment 2

[Timothy Nikkel (:tnikkel)]

Our friend GetScrolledRect. I wonder if it's worth it to try to be smart and avoid all the snapping if the destination scroll coord can't be affected by snapping (ie its definitely in the scroll range).

Comment 3

[BugBot [:suhaib / :marco]]

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

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