Bug 291514 – Collapsed table first row width quirk

• Status: RESOLVED
• Resolution: FIXED
• Component: Tables

[Karl Dubost]

http://wpt.live/css/css-tables/collapsed-scroll-overflow.html
https://wpt.fyi/results/css/css-tables/collapsed-scroll-overflow.html

Right now this test fails in WebKit while passing in blink and Gecko
assert_equals: The collapsed border does not exceed the scroll container. expected 500 but got 540

The test was the result of the discussion on 
https://github.com/w3c/csswg-drafts/issues/6230

which had this resolution from the CSS WG. 
RESOLVED: Accept current Tables 3 spec text regarding calculation of shared borders in collapsed-border mode between table and cells.

It was initially referring to https://www.w3.org/TR/2011/REC-CSS2-20110607/tables.html#collapsing-borders
> UAs must compute an initial left and right border width for the table by examining the first and last cells in the first row of the table. The left border width of the table is half of the first cell's collapsed left border, and the right border width of the table is half of the last cell's collapsed right border. If subsequent rows have larger collapsed left and right borders, then any excess spills into the margin area of the table.


This created issues for Chrome in
https://issues.chromium.org/issues/40515515
https://crbug.com/1200116

It was fixed on chromium by 
https://chromium.googlesource.com/chromium/src/+/bb1d2203d8dc3b89f34caa2dcd2ba2058795845e%5E%21/#F0

[Karl Dubost]

Created attachment 474908 [details]
rendering in safari, firefox, chrome

It currently fails in Safari 
pass in Firefox and Chrome

[Radar WebKit Bug Importer]

<rdar://problem/149675907>

[Ahmad Saleem]

Pull request: https://github.com/WebKit/WebKit/pull/58844

[EWS]

Committed 308311@main (8f695151e326): <https://commits.webkit.org/308311@main>

Reviewed commits have been landed. Closing PR #58844 and removing active labels.