[csswg-drafts] [css-text-4] Add an optional second value to `hyphenate-character` to render the unchosen `­` (#12255)

jfrech has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-text-4] Add an optional second value to `hyphenate-character` to render the unchosen `­` ==
### Status quo
Currently, `hyphenate-character`'s values are defined as (cf. https://www.w3.org/TR/css-text-4/#hyphenate-character [2025-05-31])

````
hyphenate-character = auto | <string>
````

with the semantics that when a `&shy;` word-break opportunity is taken, the `&shy;` character is rendered as the given string (which has an `auto` default). When a `&shy;` word-break opportunity isn't taken, the `&shy;` character isn't rendered.

### Proposal
I propose adding a second, optional argument to `hyphenate-character` with default value `""` that specifies the rendering of a `&shy;` character whose word-break opportunity isn't taken:

````
hyphenate-character = auto | <string> | <string> <string>
````

The rendered, untaken `&shy;` becomes part of the physical text with regards to selection ranges.

### Motivation
Hyphenation rules in modern English (e.g. `en-GB`) and German after the spelling reform (e.g. `de-DE`) fit `hyphenate-character`'s model well: when you can break, break and add a hyphen, else don't break and leave the word alone.

However, when typesetting German preceding the spelling reform (language code `de-DE-1901`), hyphenation *may add and remove letters*:

````text
((de-DE-1901))

Nach Tagen der Suche konnte sie eine Pampelmuse entdecken, und begann, ein Stilleben anzufertigen.
                                                     ^^ "ck" -> "k-k"         ^^ "ll" -> "ll-l"
    
Nach Tagen der Suche konnte
sie eine Pampelmuse entdek-
ken, und begann, ein Still-
leben anzufertigen.
````

*Adding* letters `"ll" -> "ll-l"` when breaking can be achieved with contemporary CSS:

````html
<p lang="de-DE-1901">Nach Tagen der Suche konnte sie eine Pampelmuse entdecken, und begann, ein
<span style="hyphenate-character: 'l-';">Stil&shy;le</span>&shy;ben
anzufertigen.</p>
````

But *changing* letters `"ck" -> "k-k"` when breaking, to my knowledge, cannot be achieved in pure CSS (I have written an ECMAScript resize observer which changes letters' `display: none` styling, though it possibly falls into a never-ending loop when the font rendering gives different characters too dissimilar widths).  
With an unused-`&shy;` text parameter to `hyphenate-character`, the break opportunity could be aptly described:

````html
<p lang="de-DE-1901">Nach Tagen der Suche konnte sie eine Pampelmuse
ent&shy;<span style="hyphenate-character: 'k-' 'c';">de&shy;ken</span>,
und begann, ein Stilleben anzufertigen.</p>
````

### Raison d'être
I think adding an as-described non-taken `&shy;` rendering argument to `hyphenate-character` opens up the possibility for correctly breaking justified `de-DE-1901` text, a feature CSS is currently lacking, through a generic feature without introducing `de-DE-1901`-specific styling rules.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/12255 using your GitHub account


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Received on Saturday, 31 May 2025 19:15:55 UTC