[css‑fonts‑4] Create keywords for `unicode‑range`

[ExE-Boss]

https://drafts.csswg.org/css-fonts/#unicode-range-desc

Inspired by @Crissov’s comment in #2855 (comment):

emoji world indeed make more sense in a font descriptor than as a font family.

@font-face {
  font-family: Twemoji;
  unicode-range: emoji;
} 

---

emoji would be a new <unicode‑range> keyword equivalent to enumerating all the Unicode codepoints where emoji reside.

[Crissov]

Alternatively, a list of ISO 15924 script codes could be allowed for the unicode-range font descriptor. The standard provides the special codes Zsye and 993 for emojis. Thatʼs more versatile and less spec maintenance work than keeping a custom list of keywords in CSS Fonts, but it is also less readable.

PS: #1744 was somewhat similar, requesting a language or lang descriptor, but scripts make more sense.

[svgeesus]

Adding script names or language names is a recurring request, and we do need to address it at some point. I agree with @Crissov that scripts make more sense than languages.

For example, this is both cumbersome and fragile against future additions:

@font-face {
            	font-family: 'Headings';
            	src: url(fonts/Japanese.woff);
            	unicode-range: U+A5, U+4E00-9FFF, U+30??, U+FF00-FF9F;
            	/* yen, kanji, hiragana, katakana */
            }

I agree with @Crissov that using an existing list, provided it is well maintained, well documented and readily available, is much better than getting into the business of script or language registries.

It isn't clear to me that ISO 15924:2004 defines which characters are included in each script. I wasn't keen to spend the CHF 68 to find out. Anyone know? Or is that all contained in the registry?

Unicode® Standard Annex #24 Unicode Script Property is online, and freely available, and appears to be a superset of ISO 15924.

I'm happy that the registry is online and that Unicode is the registration authority. That at least means that ISO and Unicode are striving to be in alignment here (with a few exceptions, like Fractur and Gaelige being distinct in ISO 15924 and unified in Unicode UAX 24.

I plan to reach out to the maintainers of the registry to confirm the exact status.

[svgeesus]

Hmm. From the registry

Hira;410;Hiragana;hiragana;Hiragana;1.1;2004-05-01

That says that Hiragana exists, but not which code points are covered.

[svgeesus]

The complete list is in the Scripts file. For example

# ================================================

3041..3096    ; Hiragana # Lo  [86] HIRAGANA LETTER SMALL A..HIRAGANA LETTER SMALL KE
309D..309E    ; Hiragana # Lm   [2] HIRAGANA ITERATION MARK..HIRAGANA VOICED ITERATION MARK
309F          ; Hiragana # Lo       HIRAGANA DIGRAPH YORI
1B001..1B11E  ; Hiragana # Lo [286] HIRAGANA LETTER ARCHAIC YE..HENTAIGANA LETTER N-MU-MO-2
1B150..1B152  ; Hiragana # Lo   [3] HIRAGANA LETTER SMALL WI..HIRAGANA LETTER SMALL WO
1F200         ; Hiragana # So       SQUARE HIRAGANA HOKA

# Total code points: 379

# ================================================

[faceless2]

Using the Unicode Script property as shorthand for a ranges is a really, really good idea. More intuitive, less error prone, less verbose, and it's a public list that's already baked into CSS implementations - the Unicode Script property is already referenced by css-text-3. Thumbs up to this whole issue.