1907289 - Page is slowly scrolling automatically

Status: VERIFIED FIXED

(Core :: Layout: Tables, defect)

Description

[Fabio]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

Steps to reproduce:

• Open https://tradingeconomics.com/calendar
• Scroll a bit down
• Then the automatically scrolling down starts

Actual results:

The page is going up and down, but if you look closely it's going down really slow

Expected results:

it should be a static page

Comment 1

[Fabio]

Tried on the previous firefox version and it is not happening this issue (127.02)

Comment 2

[Ryan VanderMeulen [:RyanVM]]

INFO: Last good revision: 33172968feaa0ef9043a29b0231451411bb57223
INFO: First bad revision: e7f116bf080c7d9ac0fe5fe26a04779a673018ec
INFO: Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=33172968feaa0ef9043a29b0231451411bb57223&tochange=e7f116bf080c7d9ac0fe5fe26a04779a673018ec

Comment 3

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

Set release status flags based on info from the regressing bug 1850834

:emilio, since you are the author of the regressor, bug 1850834, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 4

[Timothy Nikkel (:tnikkel)]

Moving component based on regressor.

Comment 5

[Emilio Cobos Álvarez [:emilio]]

The page is doing something odd:

        // This slows down the bind
        $(window).bind('DOMContentLoaded load resize scroll', function (e) {
            var scrollY = window.scrollY;
            if (scrollY >= 0) {
                setTimeout(function () {
                    if (window.scrollY == scrollY)
                        //console.log("calendar scrollY: " + scrollY);
                        bindIt();
                }, 250);
            }
        });

Where bindIt computes adds and removes a table cell in a way that it used to destroy the whole table and now no longer does. That somehow seems to cause scroll anchoring to kick in, and trigger another scroll event, causing the effect here.

They have a helpful debug mode with console logs: https://tradingeconomics.com/calendar?debug

I'll dig to see why scroll anchoring is kicking in.

Adding :root { overflow-anchor: none } "fixes" it.

Comment 6

[Emilio Cobos Álvarez [:emilio]]

Submitted a pernosco trace:

Compressing to /tmp/tmp82y1rcc9...
Uploading 1360397165 bytes to s3://pernosco-upload/15EaUmqxv78.tar.zst...
upload: ../../../../../tmp/tmp82y1rcc9 to s3://pernosco-upload/15EaUmqxv78.tar.zst

This is starting to look like a subtle (and probably pre-existing) layout bug, but I gotta dig more.

Comment 7

[Emilio Cobos Álvarez [:emilio]]

Attachment: Frame tree diff that shows the 30 app-units (half a pixel) difference which causes us to scroll up.

Comment 8

[Emilio Cobos Álvarez [:emilio]]

Attachment: Reduced test-case

All tables should look the same. In particular, that shift in "Test 2" shouldn't happen. Before my patch, it was papered because we rebuilt the whole table.

Comment 9

[Emilio Cobos Álvarez [:emilio]]

Attachment: More reduced test-case that shows the issue before my patch.

Yeah, so, as suspected, this basically uncovers a bug in the dynamic changes of our border-collapsed tables :'(

Comment 10

[Emilio Cobos Álvarez [:emilio]]

cc'ing David who has looked at border-collapsed tables recently, in case he has any idea off-hand of where the bug might lie. I'll debug this regardless of course.

Comment 11

[Emilio Cobos Álvarez [:emilio]]

Attachment: Bug 1907289 - Reflow table cell if collapsed borders have changed. r=dshin!

A potentially better approach could be to call FrameNeedsReflow from
nsBCTableCellFrame::SetBorderWidth... But it seems that might
over-invalidate quite a lot when recalculating borders, since it seems
we reset the relevant ones and then accumulate directly on the frame.

If that seems like a better approach, happy to give that a try. This
should be less risky for performance changes in general tho.

Comment 12

[Emilio Cobos Álvarez [:emilio]]

Comment on attachment 9412498 [details]
Bug 1907289 - Reflow table cell if collapsed borders have changed. r=dshin!

Beta/Release Uplift Approval Request

• User impact if declined: comment 0
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: comment 0
• List of other uplifts needed: none
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Relatively low-risk fix for a pre-existing issue that the regressing bug uncovered.
• String changes made/needed: none
• Is Android affected?: Yes

Comment 13

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a3485259ae0c
Reflow table cell if collapsed borders have changed. r=dshin

Comment 14

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/47115 for changes under testing/web-platform/tests

Comment 15

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/a3485259ae0c

Comment 16

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot

Comment 17

[Donal Meehan [:dmeehan]]

Comment on attachment 9412498 [details]
Bug 1907289 - Reflow table cell if collapsed borders have changed. r=dshin!

Approved for 129.0b4

Comment 18

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/e99ab93d0183

Comment 19

[Catalin Sasca, Desktop Test Engineering [:csasca]]

Reproduced the issue on Firefox 130.0a1 (2024-07-11) on Windows 11 by following the STR from Comment 0.

The issue is fixed on Firefox 129.0b4 (treeherder build) and Firefox 130.0a1 (2024-07-14). Tests were performed on macOS 14.5, Windows 11 and Ubuntu 24.04.

Will verify the fixes on 128 and ESR128 as well when they will be available.

Comment 20

[Donal Meehan [:dmeehan]]

Comment on attachment 9412498 [details]
Bug 1907289 - Reflow table cell if collapsed borders have changed. r=dshin!

Approved for 128.1esr.

Comment 21

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-esr128/rev/19bda7044b35

Comment 22

[Ryan VanderMeulen [:RyanVM]]

Comment on attachment 9412498 [details]
Bug 1907289 - Reflow table cell if collapsed borders have changed. r=dshin!

Approved for 128.0.2

Comment 23

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-release/rev/9296cb000661

Comment 24

[Catalin Sasca, Desktop Test Engineering [:csasca]]

Verified the fix on Firefox 128.0.2 and Firefox 128.1.0esr (treeherder build). Tests were performed on macOS 14.5, Windows 11 and Ubuntu 24.04.