ishida >> blog

I see from a recent bugzilla report and some cursory testing that a (very) long-standing bug in Mozilla related to complex scripts has now been fixed.

Complex scripts include many non-Latin scripts that use combining characters or ligatures, or that apply shaping to adjacent characters like Arabic script.

It used to be that, when you highlighted text in a complex script, as you extended the edges of the highlighted area you would break apart combining characters from their base character, split ligatures and disrupt the joining behaviour of Arabic script characters.

The good news is that this no longer happens – it was fixed by the new text frame code. The bad news is that the highlighting still happens character by character, rather than at grapheme boundaries – which can make it tricky to know whether you got the combining characters or not.

UPDATE: I hear from Kevin Brosnan that the following will be fixed in Firefox 3. Hurrah! And thank you Mozilla team.

What doesn’t appear to be fixed is the behaviour of asian scripts when the CSS text-align:justify is applied.

I raised a bug report about this. I was amazed, after hearing about this from Indians and Pakistanis too, that there didn’t seem to be a bug report already. Come on users, don’t leave this up to the W3C!

Basically, the issue is that if you apply text-align: justify to some text in an Indian or Tibetan script the combining characters all get rendered alongside their base characters, ie. you go from this (showing, respectively, tibetan, devanagari (hindi and nepali), punjabi, telegu and thai text):

to this:

Strangely the effect doesn’t seem to apply to the Thai text, nor to other text with combining characters that I’ve tried.

That’s a pretty big bug for people in the affected region because it effectively means that text-align:justify can’t be used.

Ruby text above and below Japanese characters.

My last post mentioned an extension that takes care of Thai line breaking. In this post I want to point to another useful extension that handles ruby annotation.

Typically ruby is used in East Asian scripts to provide phonetic transcriptions of obscure characters, or characters that the reader is not expected to be familiar with. For example it is widely used in education materials and children’s texts. It is also occasionally used to convey information about the meaning of ideographic characters. For more information see Ruby Markup and Styling.

Ruby markup (called 振り仮名 [furigana] in Japan) is described by the W3C’s Ruby Annotation spec. It comes in two flavours, simple and complex.

Ruby markup is a part of XHTML 1.1 (served as XML), but native support is not widely available. IE doesn’t support XHTML 1.1, but it does support simple ruby markup in HTML and XHTML 1.0. This extension provides support in Firefox for both simple and complex ruby, in HTML, XHTML 1.0 and XHTML 1.1.

It passes all the I18n Activity ruby tests, with the exception of one *very* minor nit related to spacing of complex ruby annotation.

Before and after applying the extension.

Samphan Raruenrom has produced a Firefox extension based on ICU to handle Thai line breaking.

Thai line breaks respect word boundaries, but there are no spaces between words in written Thai. Spaces are used instead as phrase separators (like English comma and full stop). This means that dictionary-based lookup is needed to properly wrap Thai text.

The current release works on Windows and the current Firefox release, 2.0.0.4. The next release will also support Linux and will support future Mozilla Firefox/Thunderbird releases.

You can test this on our i18n articles translated into Thai.

This replaces work on a separate Thai version of Firefox.

Christopher Fynn of the National Library of Bhutan raised an interesting question on the W3C Style and I18n lists. Tibetan emphasis is often achieved using one of two small marks below a Tibetan syllable, a little like Japanese wakiten. The picture shows U+0F35: TIBETAN MARK NGAS BZUNG NYI ZLA in use. The other form is 0F37: TIBETAN MARK NGAS BZUNG SGOR RTAGS.

Chris was arguing that using CSS, rather than Unicode characters, to render these marks could be useful because:

• the mark applies to, and is centred below a whole ’syllable’ – not just the stack of the syllable – this may be easier to achieve with styling than font positioning where, say, a syllable has an even number of head characters (see examples to the far right in the picture)
• it would make it easier to search for text if these characters were not interspersed in it
• it would allow for flexibility in approaches to the visual style used for emphasis – you would be able to change between using these marks or alternatives such as use of red colour or changes in font size just by changing the CSS style sheet (as we can for English text).

There are of potential issues with this approach too. These include things like the fact that the horizontal centring of glyphs within the syllable is not trivial. The vertical placement is also particularly difficult. You will notice from the attached image that the height depends on the depth of the text it falls below. On the other hand, it isn’t easy to achieve this with diacritics either, given the number of possible permutations of characters in a syllable. Such positioning is much more complicated than that of the Japanese wakiten.

A bigger issue may turn out to be that the application for this is fairly limited, and user agent developers have other priorities – at least for commercial applications.

To follow along with, and perhaps contribute to, the discussion follow the thread on the style list or the www-international list.