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[csswg-drafts] [css-content][selectors] :level(an+b) Pseudo Class

From: Christoph Päper via GitHub <sysbot+gh@w3.org>
Date: Thu, 28 Jul 2016 08:16:56 +0000
To: public-css-archive@w3.org
Message-ID: <issues.opened-168038513-1469693815-sysbot+gh@w3.org>
Crissov has just created a new issue for 
https://github.com/w3c/csswg-drafts:

== [css-content][selectors] :level(an+b) Pseudo Class ==
The [generation of bookmark 
levels](https://drafts.csswg.org/css-content/#bookmark-generation) has
 been discussed e.g. in #204 and [in November 2015 on 
www-style](https://lists.w3.org/Archives/Public/www-style/2015Nov/0310.html).
 @frivoal had shown that it’s nearly impossible to recreate the HTML5 
outline algorithm with existing Selectors, so `bookmark-level: auto` 
would make some sense. That value hasn’t been added to the drafts, 
though, and I would like to propose a different solution, a new 
pseudo-class.

Nesting, stacking or hierarchy levels are of interest for styling in 
several cases, e.g. headings or sections and lists in document markup 
languages or layers and sprites in images. So let there be an abstract
 **level** that depends on the host language and may differ among its 
element types. Since a pseudo class increases specify, the followin 
rulesets should describe the usually desired behavior for HTML:

    :level(0) { bookmark-level: none; }
    h1, h2:level(1), h3:level(1), h4:level(1), h5:level(1), 
h6:level(1) { bookmark-level: 1; }
    h2, h1:level(2), h3:level(2), h4:level(2), h5:level(2), 
h6:level(2) { bookmark-level: 2; }
    h3, h1:level(3), h2:level(3), h4:level(3), h5:level(3), 
h6:level(3) { bookmark-level: 3; }
    h4, h1:level(4), h2:level(4), h3:level(4), h5:level(4), 
h6:level(4) { bookmark-level: 4; }
    h5, h1:level(5), h2:level(5), h3:level(5), h4:level(5), 
h6:level(5) { bookmark-level: 5; }
    h6, h1:level(6), h2:level(6), h3:level(6), h4:level(6), 
h5:level(6) { bookmark-level: 6; }

The syntax inside parentheses would probably follow the existing 
`an+b` syntax, but I‘m not sure we’d need to differentiate 
`:first-level`, `:last-level` and `:nth-level()`, but it would be 
consistent.

Likewise, one could easily ensure the same marker style for items in 
nested lists, no matter if the structure mixes `ol`, `ul` and `dl`.

    ul>li:level(2) { list-style-type: disc; }

Please view or discuss this issue at 
https://github.com/w3c/csswg-drafts/issues/351 using your GitHub 
account
Received on Thursday, 28 July 2016 08:17:13 UTC

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