Bug 235525 – Browsers don't hyphenate Mongolian text

• Status: NEW
• Component: Layout and Rendering

[r12a]

Hyphenation occurs in writing Mongolian and Todo. U+1806 MONGOLIAN TODO SOFT HYPHEN is used to indicate resumption of a broken word. It functions like U+2010 HYPHEN, except that it appears at the beginning of a line rather than at the end. (Note that lines of Mongolian text are vertical, and progress from left to right.)

Specs:
issue Better describe the likely outcomes of hyphenation Open.
https://github.com/w3c/csswg-drafts/issues/5973

css-text Describes how to apply hyphenation. It makes no special mention of Mongolian, nor of which character to use and where.
https://drafts.csswg.org/css-text-3/#hyphenation

css-text Has a hyphenate-character property which will allow users to specify the character to use for hyphenation, but it doesn't allow control of the location of the character.
https://drafts.csswg.org/css-text-4/#hyphenation

Actual results:

Note: Webkit is unable to display traditional Mongolian script, so this is a secondary problem.  It still needs to be logged, however, so that it can be fixed for Mongolian content authors once they are able to use WebKit browsers.

Interactive test, Mongolian text is hyphenated when hyphens:auto is set
https://github.com/w3c/line_paragraph_tests/issues/64
Gecko: ❌ Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:94.0) Gecko/20100101 Firefox/94.0
Blink: ❌ Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36
Webkit: ❌ Safari doesn't display correctly. Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.1 Safari/605.1.15

Interactive test, Mongolian adds a hyphen to the start of the second line when a word is manually hyphenated with SHY
https://github.com/w3c/line_paragraph_tests/issues/65
Gecko: ? Produces a vertical baseline extension at the bottom of the first line. Not clear whether this is just part of the cursive glyph or a hyphen.. Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:94.0) Gecko/20100101 Firefox/94.0
Blink: ❌ Produces a horizontal hyphen at the bottom of the first line. Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36
Webkit: ❌ Unable to correctly display traditional Mongolian script. Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.1 Safari/605.1.15

i18n test suite, CSS3 Text, hyphens
https://www.w3.org/International/i18n-tests/results/hyphens#auto
General tests for hyphens support. (Results may need updating.)

Expected results:

Please enable hyphenation for Traditional Mongolian text, and show the correct hyphenation character at the start of the second line.

[Radar WebKit Bug Importer]

<rdar://problem/88276524>

[Fuqiao Xue]

Should we close this, per https://github.com/w3c/mlreq/issues/40#issuecomment-2519990316 ?