[css-values-4] Support ic unit ("水" CJK water ideograph, U+6C34)

• Component: CSS
• Status: RESOLVED FIXED

[Gérard Talbot]

CSS4 Values and Units, 6.1.1. Font-relative lengths section, ic unit
https://www.w3.org/TR/css-values-4/#ic
states

"
ic unit
Equal to the used advance measure of the “水” (CJK water ideograph, U+6C34) 
glyph found in the font used to render it.

This measurement is a typically an exact measure (in the few fonts with 
proportional fullwidth glyphs, an approximation) of a **single fullwidth 
glyph’s advance measure**, thus allowing measurements based on an expected 
glyph count.

In the cases where it is impossible or impractical to determine the 
ideographic advance measure, it must be assumed to be 1em.
"

9 Tests
-------

In horizontal-tb writing-mode:
http://w3c-test.org/css/css-values/ic-unit-001.html

With text-orientation: upright; and writing-mode: vertical-rl;
http://w3c-test.org/css/css-values/ic-unit-002.html

With text-orientation: mixed; and writing-mode: vertical-rl;
http://w3c-test.org/css/css-values/ic-unit-003.html

With text-orientation: sideways; and writing-mode: vertical-rl;
http://w3c-test.org/css/css-values/ic-unit-004.html

In horizontal-tb writing-mode:
http://w3c-test.org/css/css-values/ic-unit-008.html

With (initial) text-orientation: mixed; and writing-mode: vertical-rl;
http://w3c-test.org/css/css-values/ic-unit-009.html

With text-orientation: mixed; and writing-mode: vertical-rl;
http://w3c-test.org/css/css-values/ic-unit-010.html

With text-orientation: upright; and writing-mode: vertical-rl;
http://w3c-test.org/css/css-values/ic-unit-011.html

With text-orientation: sideways; and writing-mode: vertical-rl;
http://w3c-test.org/css/css-values/ic-unit-012.html


Right now, no browser supports any of these 9 tests

https://wpt.fyi/results/css/css-values?label=master

I searched for duplicate and did not find any.

[Gérard Talbot]

Correspondent Mozilla Bug report
https://bugzilla.mozilla.org/show_bug.cgi?id=1531223

[Radar WebKit Bug Importer]

<rdar://problem/48532261>

[Myles C. Maxfield]

+1 to this request. This should happen.

[Gérard Talbot]

Correspondent Blink Bug report
https://bugs.chromium.org/p/chromium/issues/detail?id=937101

[Kiet Ho]

Resolved in https://bugs.webkit.org/show_bug.cgi?id=204276