Hi Ed, I put together a New Tai Lue shaper for hb-ng a while ago, as a simple example of a script needing minor reordering. The patch was forwarded to the hb mailing list on March 3, 2011 (see message "Shape for New Tai Lue"), if you'd like to have a look; that might provide you with a starting-point.
JK On 22 Apr 2011, at 17:31, Ed wrote: > Hi, Behdad and other HB contributors, > > As some of you know, I'm working on creating a Unicode font for the > Tai Tham script which is one of the many Brāhmī-derived abugidas of > Southeast Asia (our project URL: http://hariphunchai.unifont.org/ ). > > Like other Indic scripts, Tai Tham shaping is complex and requires > reordering of certain glyphs. Currently, no operating system provides > support for Tai Tham re-ordering. However Tai Tham's re-ordering > requirements are much simpler than (for example) those Devanagari. > > As it seems that HarfBuzz is now reaching a more mature state, I am > hoping that now is a good time to bring up the idea of having HB > support Tai Tham re-ordering. > > Here, in general, is what is required: > > (1) U+1A55 TAI THAM CONSONANT SIGN MEDIAL RA needs to be reordered to > appear *before* a consonant cluster (CC): > > LOGICAL BACKSTORE => VISUAL LAYOUT > <CC> + <U+1A55> => <U+1A55><CC> > > (2) The following five Prefixed Dependent Vowel (PDV) signs, U+1A6E, > U+1A6F, U+1A70, U+1A71, U+1A72, need to be reordered to appear > *before* a consonant cluster (CC) which may include MEDIAL RA (w/MR): > > <CC> + <PDV> => <PDV><CC> > <CCw/MR> + <PDV> => <PDV><CCw/MR> > > That's about it! > > There are other features of Tai Tham, such as subjoined consonants, > but I believe only the 2 features above require specialized shaper > code while everything else can be achieved using standard OpenType > features such as GSUB without resorting to specialized shaper code. > > Note that if Tai Tham is implemented, then it will be simple to > implement other 'Tai' scripts like Tai Viet and New Tai Lue that have > very similar features. > > Anyone interested in helping sort this out, please contact me. Thanks! - Ed > _______________________________________________ > HarfBuzz mailing list > [email protected] > http://lists.freedesktop.org/mailman/listinfo/harfbuzz _______________________________________________ HarfBuzz mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/harfbuzz
