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Re: [css3-text-layout] New editor's draft - margin-before/after/start/end ?etc.

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 4 Jun 2010 08:44:25 -0700
Message-ID: <AANLkTinI9ZlhlvD_jpfuQaGWwlS4DKYTcqvVUqMGC7qr@mail.gmail.com>
To: "MURATA Makoto (FAMILY Given)" <eb2m-mrt@asahi-net.or.jp>
Cc: www-style@w3.org
On Fri, Jun 4, 2010 at 6:18 AM, MURATA Makoto (FAMILY Given)
<eb2m-mrt@asahi-net.or.jp> wrote:
> Håkon,
> Your modified :ttb proposal (not the modified :lang proposal) addresses
> the requirement to a certain extent.
>> So, the pseudo-class selectors would mean:
>>   :lrt   horizontal writing is supported and @dir has been set to 'lrt'
>>   :rtl   horizontal writing is supported and @dir has been set to 'rtl'
>>   :ttb   vertial writing is supported
> However, I am not sure if I like this proposal.
> First, what is needed is  relativity based on the principal writing mode
> chosen by the browser or user rather than relativity based on the
> capability of the browser.  Even if a browser supports vertical writing,
> the pseudo selector should not apply when the user chooses
> horizontal writing as the principal writing mode (the writing mode of the body
> element)

Agreed that they should match dynamically based on the current mode,
not whether something is supported or not.

> Second, I think :rtl and :ttb are just too different.  The former is
> based on the @dir attribute, while the latter is not.   They should
> be separated.

They do indeed come from different sources, but they describe similar
problems.  Many of the issues that you have with laying out a document
different in horizontal and vertical writing modes apply equally
*within* horizontal writing when you swap from ltr to rtl.  That is to
say, the start/end directions is important to both rtl and ttb writing
modes (the before/after directions are less important to purely
horizontal writing modes).

> Third, are there any requirements for :rtl?  Isn't [dir="rtl"]
> good enough?

No, as explained previously; @dir "inherits" down the tree, so in
order to use just @dir you have to constantly use descendant
selectors.  An :ltr/:rtl pseudo lets you directly get at the direction
information that each element carries around anyway.

> Fourth, Japanese and Taiwanese users will need a pseudo selector
> for horizontal writing.  It has nothing to do with the @dir attribute
> but it should apply when the browser or user chooses "horizontal"
> as the principal writing mode.

When they are written horizontally, presumably they act like any other
horizontally-written language, and thus go either right-to-left or
left-to-right, correct?  If so, then using :ltr or :rtl (whichever is
appropriate) would let you apply rules for only horizontal writing.

> Fifth, I have no ideas about where in the CSS3 family of specifications
> the :ttb psuedo selector will be introduced.

Being a selector, it would show up in CSS4 Selectors.

> Sixth, *-before, etc. is already described in a editor's draft.
> It may be sketchy, but it is in the draft.  But :ttb is just an idea.

That's mostly irrelevant.  Being in a draft versus an email doesn't
afford an idea any special status.  Hopefully the idea in the draft is
somewhat more fleshed out and detailed, but that's it.

Received on Friday, 4 June 2010 15:45:17 UTC

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