[HarfBuzz] Verbose shaping process information

[Behdad Esfahbod]

On 14-08-30 05:07 PM, Olivier Berten wrote:
> Hi!

Hi Olivier,


> Is there a way to see what Harbuzz is doing step by step in order to
> debug font features?

No, not currently.


> Something like:
> Input string: <U+xxxx, U+yyyy, U+zzzz>
> Requested features: ss01
> Using XXXX engine
> Reordering string: <U+xxxx, U+wwww, U+zzzz, U+yyyy>
> Switching to glyphs level: <unixxxx, uniwwww, unizzzz, uniyyyy>
> Applying 'pref' (1 substitution): <unixxxx, uniwwww, unizzzz_alt, uniyyyy>

This last part is the most interesting one to most people.  It's not
straightforward though, since OpenType structures substitutions into lookups,
and multiple lookups can be referenced from each feature.  So the mapping is
not as clear cut as expected.

That said, this is frequently requested, and extremely useful in my own
debugging too, so I have had wanted to add it.  Will take a look after I'm
back from vacation.

behdad

> etc.
> 
> Yours,
> 
> Olivier
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-- 
behdad
http://behdad.org/