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Re: [css-logical-props] do shorthands have logical component longhands?

From: Simon Pieters <simonp@opera.com>
Date: Mon, 05 Jan 2015 10:47:38 +0100
To: "Cameron McCormack" <cam@mcc.id.au>, "L. David Baron" <dbaron@dbaron.org>
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, "www-style list" <www-style@w3.org>
Message-ID: <op.xrzhhomsidj3kv@simons-mbp>
On Sun, 21 Dec 2014 01:07:06 +0100, L. David Baron <dbaron@dbaron.org>  
wrote:

> On Sunday 2014-12-21 10:22 +1100, Cameron McCormack wrote:
>> (2) Here is a case where assigning to a shorthand gives you (what I
>> think might be) unintuitive results:
>>
>>   div { margin: 1px;
>>         margin-inline-start: 0px; margin-inline-end: 0px;
>>         margin-block-start: 0px; margin-block-end: 0px; }
>>
>>   decl.style.margin = "2px";
>>
>> Since the declaration has all of the component longhands already, we
>> just overwrite each one with either 2px (for the physical ones) or
>> 0px (for the logical ones).  The result is that you'll still have
>> 0px margins, as the logical properties still appear after the
>> physical ones.
>
> Well, I wish setProperty always had append semantics (which I should
> perhaps call remove-and-append semantics), but it may be too late to
> go back to that.
>
> I believe it had remove-and-append semantics in Gecko prior to:
> https://bugzilla.mozilla.org/show_bug.cgi?id=288574 which switched
> to replace-or-append, although we've since added additional
> optimizations that depend on the replace-or-append semantics in:
> https://bugzilla.mozilla.org/show_bug.cgi?id=498562 .
>
> (By replace-or-append, I mean the algorithm in
> http://dev.w3.org/csswg/cssom/#set-a-css-declaration .
> Remove-or-append semantics would mean changing step 1 of that
> algorithm to remove the existing declaration, and then dropping the
> "Otherwise" from step 2.)
>
> (This is related to the debate we had last year about !important,
> http://lists.w3.org/Archives/Public/www-style/2013Sep/thread.html#msg201
> http://lists.w3.org/Archives/Public/www-style/2013Oct/thread.html#msg2
> in which I eventually gave in.)
>
>> Should we make assigning to 'margin' move the physical properties to
>> the end of the declaration?  (And if we do so, we'll need to ensure
>> that the empty string is returned when getting 'margin' if logical
>> properties appear after physical ones.)
>
> Well, it would probably need to move the physical and logical
> properties, once the 'logical' keyword is introduced.
>
> This is a bit of a mess; I don't see a good solution unless we can
> switch to append semantics for setProperty instead of
> replace-or-append.  (I'm curious if the current replace-or-append is
> fully interoperable.  Gecko did once do remove-and-append.)

http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3348

WebKit/Blink/Gecko/IE11 do replace-or-append, Presto does  
remove-and-append.

-- 
Simon Pieters
Opera Software
Received on Monday, 5 January 2015 09:46:59 UTC

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