Bug 312831 – REGRESSION (307593@main): position-area box in fast/scrolling/anchor-overscroll-fixed.html does not fallback properly

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Kiet Ho]

Created attachment 479223 [details]
Screen recording of the issue

Steps to reproduce:
* Open fast/scrolling/anchor-overscroll-fixed.html
* Scroll up and down to make the teal box and aqua (border only) box change position due to position option fallback

Expect: the teal and aqua box should fallback with each other
Actual: the teal box does not fallback at all.

Attached is a video of the issue on WebKit 307593@main.

[Radar WebKit Bug Importer]

<rdar://problem/175203020>

[fantasai]

I can't get a working build atm, but I think you should be able to fix the problem by removing these two lines in RenderBox::containingBlockRangeForPositioned() that are conditioned on `isFixedPositioned()`:

            if (!style().positionArea().isNone() && renderView->hasRenderOverflow())
                return getScrollableContainingBlockRange(*renderView, physicalAxis);

I'm trying to think why those two lines were added and coming up blank. So hopefully it's ok to just remove them. :)

Don't remove the ones at the bottom of the function, or that'll regress non-fixed-positioned boxes.

[fantasai]

Filed a follow-up on testing at https://bugs.webkit.org/show_bug.cgi?id=313020 fwiw.

[Kiet Ho]

Pull request: https://github.com/WebKit/WebKit/pull/63363

[Kiet Ho]

Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/59454

[EWS]

Committed 311981@main (aac4aed489d1): <https://commits.webkit.org/311981@main>

Reviewed commits have been landed. Closing PR #63363 and removing active labels.

[EWS]

Committed 305413.728@safari-7624-branch (294b842176b7): <https://commits.webkit.org/305413.728@safari-7624-branch>

Reviewed commits have been landed. Closing PR #5048 and removing active labels.