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[csswg-drafts] [css-text] Ignore Variation Selectors

From: Christoph Päper via GitHub <sysbot+gh@w3.org>
Date: Thu, 04 Jan 2018 21:58:35 +0000
To: public-css-archive@w3.org
Message-ID: <issues.opened-286125861-1515103114-sysbot+gh@w3.org>
Crissov has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-text] Ignore Variation Selectors ==
In #1144 I proposed a property to remove, add or override [Unicode Variation Selectors](http://unicode.org/faq/vs.html) (‘VS’, chiefly U+FE0x) from/to all applicable characters. The main use case presented was consistent presentation of possible emoji characters by enforcing either VS-15 or VS-16. The WG decided against adding an `override` keyword to the `font-presentation` property. I am now proposing `text-transform-variant` again, but limited to stripping (or keeping) *all* VSs.

Variation selectors by definition do not change the semantics of the character varied. While emoji variation sequences usually come in pairs, others only document one specific variant, e.g. a slashed digit zero vs. the default design, which may depend on the font features set (OT `zero`, CSS `font-variant-numeric: slashed-zero`). Most variation sequences come in groups that are using VSs (usually VS-1 and VS-2) in a consistent way (but math symbols hardly do), e.g. Myanmar characters may be switched to a _dotted form_. This means variation sequences are close to or even crossing the border between character encoding and typography, hence design. They thus become in scope of CSS.

Changing the variant can usually be considered less consequential than changing letter case. It is also much more simple to implement because it only involves dropping certain Unicode Code points. Font selection should not be affected for non-emoji sequences, because it is always expected that only the base glyph without variation may be displayed. (Some emoji fonts only contain colorful glyphs which in many cases are only appropriate if VS-16 was present; e.g.  Symbola, on the other hand, only contains text-like characters which can also be considered inappropriate for one class of emojis.)

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/2166 using your GitHub account
Received on Thursday, 4 January 2018 21:58:36 UTC

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