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.