Re: [css-text][css-conditional] language specific support for hyphenation and justification

On Tue, Jun 16, 2015 at 10:24 PM, Florian Rivoal <florian@rivoal.net> wrote:

> Many people (here's one example[1]) recommend that justification should
> only be used if you can also do hyphenation, as otherwise it looks bad.
>
> To do that in a browser, you may be tempted to write this:
>
>   p { text-align: left; }
>   @supports (hyphens: auto) {
>     p {
>       hyphens: auto;
>       text-align: justify;
>     }
>   }
>
> However, it doesn't quite do cut it.
>
> * Problem 1
>
> Support for hyphenation is language dependent. Even if a browser properly
> implements the 'hyphens' property, it may not have a dictionary to do it
> for the language at hand.
>
> * Problem 2
> "justification should only be done if you can also do hyphenation" is only
> true in some languages. For example, Japanese does not use hyphenation to
> do justification (See [2] for how it's done instead), and languages using
> the Arabic script can do pretty justification using kashida[3].
>
> Problem 1 would be addressed if we added something like
>   @supports hyphenation-language(fr) {...}
> but it seems awfully specific and narrow.
>
> Problem 2 can be handled by authors using :lang() selectors, so it is less
> of an issue. However, for stylesheets meant to be used over an open ended
> set of languages, being exhaustive is really tedious, and authors are
> unlikely to have the linguistic knowledge to do this properly.
>
> We could generalize a little bit, and go with something like (to be
> bikesheded):
>   @supports nice-justification(fr) {...}
> where the condition evaluates to true if one of the following is true:
> - The language should use hyphenation and the browser has the necessary
> resources to do it
> - The language should use some other approach (kashida, etc) and the
> browser knows how to do at least one of the acceptable techniques
> - The language is known not to need any language-specific algorithm or
> resource to justify well
>
> This is broader than @supports hyphenation-language(), but not by a whole
> lot, and it deciding which languages need what may be quite controversial,
> so I am not sure that's a great idea either.
>
> Any idea on how to solve this well?
>

It sounds like a valid use case, but I'm concerned about extending the
grammar of @supports.

What about adding values to hyphens property which allow authors to specify
the language the user agent should use for hyphenating, e.g. "p { hyphens:
lang(fr); }" or "p { hyphens: lang-fr; }", and then require the user agent
to consider a value invalid if the language specified is not supported.

In this way, we don't need to extend the grammar of @supports. In addition,
we provide more detailed control to authors about the hyphenating, although
other than being a condition, those values are almost useless.

- Xidorn