[HarfBuzz] Change in HarfBuzz after version 0.90 ?

Ed Trager ed.trager at gmail.com
Fri Dec 27 10:05:05 PST 2013

Hi, Johnathan,

In your patch:

+    /* XXX This hack belongs to the SEA shaper (for Tai Tham):

+       reorder SAKOT to ensure it comes after any tone marks. */

+    if (unlikely (unicode == 0x1A60)) return 254;

... could the return value be something a bit more symbolic?  Just so that
people like me who don't really have time to delve into the details of
HarfBuzz code will have a better hint about what the "254" represents in
this case?

Just my 2 cents, thanks! ;)

- Ed

On Fri, Dec 27, 2013 at 12:09 PM, Jonathan Kew <jfkthame at googlemail.com>wrote:

> On 27/12/13 16:21, Ed Trager wrote:
>> Hi, Martin, Richard, and Danh Hong,
>> With regard to forcing the re-ordering of the
>> UCD-enforced-but-totally-broken normalisation of TAI THAM TONE MARK plus
>> U+1A60, does the following approach in the OpenType feature file make
>> sense as the quickest and cleanest way to do it or not?:
>> Basically the idea is to compose the out-of-order pair of characters
>> into a ligature; and then take that ligature and decompose it back to a
>> pair of characters that are in the correct order:
>> If there is a better way to do this in OpenType, please enlighten me!
>> :-)  I was trying to get this to work last night, so far without success:
> The trouble with this idea (or at least one trouble with it!) is that by
> the time your lookups have a chance to do anything, harfbuzz has already
> inserted dotted-circle glyphs because it treated the (normalized) sequence
> as being a "broken" cluster. The pattern for a "consonant syllable" in the
> SEAsian shaper allows for a <sakot, consonant> pair (i.e. a subjoined
> consonant) among the various possible syllable-tail items, but it does not
> allow for the <sakot> and <cons> to be separated by other marks, which is
> what the normalization does.
> You -might- be able to work around this by explicitly including the dotted
> circles in your ligature-composition rules, though that will make them all
> more cumbersome. The better way forward is for us to fix harfbuzz, as
> previously suggested.
> Possible patch attached; Behdad, wdyt?
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