[Webkit-unassigned] [Bug 256754] Align with 'UA' Stylesheet for 'lists' by changing '1__qem' to '1em' for `margin-block-start`

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=256754

Karl Dubost <karlcow at apple.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |zalan at apple.com

--- Comment #4 from Karl Dubost <karlcow at apple.com> ---
tldr:
* safe to remove from html.css
* Quirk Unit code could be removed in another bug(?) Let's ask Alan?


Details:

Before making a decision on that, it would be good to check in the code.
I see in the code some specific usage for qem

* CSS_QUIRKY_EMS
  https://searchfox.org/wubkat/search?q=CSS_QUIRKY_EMS&path=&case=false&regexp=false
* isQuirkyEms()
  https://searchfox.org/wubkat/search?q=isquirkyems&path=&case=false&regexp=false

isQuirkyEms is not used at all in the code, apart its declaration. Probably can be removed. 

https://searchfox.org/wubkat/rev/622bd3bfe173b244d3cc68f2cb14ebbf987e14dd/Source/WebCore/css/parser/CSSPropertyParserHelpers.cpp#542-545

        case CSSUnitType::CSS_QUIRKY_EMS:
            if (parserMode != UASheetMode)
                return std::nullopt;
            FALLTHROUGH;

and other cases with no difference with the standard ems. 

but I'm not even sure it has the impact it had in the past.
https://searchfox.org/wubkat/rev/622bd3bfe173b244d3cc68f2cb14ebbf987e14dd/Source/WebCore/css/CSSUnits.h#121-125

    // This value is used to handle quirky margins in reflow roots (body, td, and th) like WinIE.
    // The basic idea is that a stylesheet can use the value __qem (for quirky em) instead of em.
    // When the quirky value is used, if you're in quirks mode, the margin will collapse away
    // inside a table cell. This quirk is specified in the HTML spec but our impl is different.
    CSS_QUIRKY_EMS

https://bugs.webkit.org/show_bug.cgi?id=204101

Is the implementation handling it now directly?
https://searchfox.org/wubkat/rev/622bd3bfe173b244d3cc68f2cb14ebbf987e14dd/Source/WebCore/layout/formattingContexts/table/TableFormattingGeometry.cpp#46-62

when this was written?
https://searchfox.org/wubkat/commit/ab3b5a332211ad9e67239fe06dce4ec9f5d155b7

I wonder if all of this can be retired



Probably it would be safe to remove from the css. 
https://searchfox.org/wubkat/search?q=_qem&path=&case=false&regexp=false

And there is a need for a followup bug on removing the QEM code.

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-unassigned/attachments/20230522/4d9a9036/attachment.htm>