[HarfBuzz] Question about HarfBuzz-ng CTL Shaper Status

Ed ed.trager at gmail.com
Thu Sep 16 07:29:17 PDT 2010

On Thu, Sep 16, 2010 at 3:42 AM, Jonathan Kew <jonathan at jfkew.plus.com> wrote:
> On 16 Sep 2010, at 02:33, Ed wrote:
>> Hi, Behdad and everyone,
>> Just want to confirm something:
>> I thought Harfbuzz-ng did not yet have "complex text shaper" support.
>> But in Firefox 4 beta with gfx.font_rendering.harfbuzz.level set to 1,
>> Devanagari and Arabic looks correct.  So shapers are present then?
> No. Firefox is using harfbuzz only for certain "simple" scripts such as Latin; it falls back to platform code (CoreText on OS X, Uniscribe on Windows) for complex scripts.

And old Pango-harfbuzz-whatever on Linux?

Also, if I am trying to test Tai Tham Unicode fonts which utilize
OpenType features such as mark-to-base (mark), mark-to-mark (mkmk),
and contextual ligatures (clig) --but doing so using Latin "dflt"
since there is no tag for Tai Tham-- is Firefox 4x really using
Harfbuzz-ng or not?

It seems possible --even likely given the kinds of results I am seeing
so far-- that Firefox is perhaps marking the runs of text as being Tai
Tham and so would not be using the new Harfbuzz-ng

And is there any possible way to know what renderer FF is really using
for any given run of text.  I guess the answer is probably not ...

- Ed

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