[HarfBuzz] The canonical ordering of hamza marks

[Khaled Hosny]

On Mon, Sep 10, 2012 at 07:36:19PM +0100, Jonathan Kew wrote:
> On 2/9/12 05:07, Khaled Hosny wrote:
> >On Sat, Sep 01, 2012 at 06:40:40PM -0400, Behdad Esfahbod wrote:
> >>On 08/26/2012 07:15 PM, Khaled Hosny wrote:
> >>>Hi Behdad,
> >>>
> >>>I just noticed that hamza above and below marks (U+0654, U+0655), are
> >>>reordered after Arabic vowel marks because they have much higher
> >>>combining classes, 230 and 222 (the "generic" combining class above and
> >>>below, respectively), which breaks mkmk positioning.
> >>>
> >>>I tried to make a patch to handle them like the shadda, but I'm not sure
> >>>how safe it is with such generic combining classes.
> >>
> >>Khaled,
> >>
> >>Given that there's a few handfuls of Arabic marks with 220/230 ccc, can you
> >>help me figure out what the expected behavior is, in respect to the main marks
> >>and shadda?  I can try to implement that after.
> >
> >Ideally, I think hamza and madda should come first, then shadda, then
> >the vowel marks then everything else:
> >
> >* hamzat and maddat: U+0653-U+0655, U+065F, U+0674, U+06E4
> >* shadda: U+0651
> >* vowel marks: U+064B-U+0650, U+0652, U+0656-U+065E, U+08F0-U+08F2
> >
> 
> The ordering of madda and vowel marks was raised on the Unicode list
> in July 2011, and at that point the responses indicated that madda
> should *follow* vowel marks; see
> http://www.unicode.org/mail-arch/unicode-ml/y2011-m07/0143.html and
> its replies.

Even without reading the replies, this makes perfect sense (fr Quranic
usage at least, ordinary Arabic use of madda wouldn't combine it with
vowel marks anyway).

Regards,
 Khaled