I discovered there was an issue when I tried using a test font I created
with the following as one of its lookups (in ttx format):
<Lookup index="1">
<LookupType value="1"/>
<LookupFlag value="0"/>
<!-- SubTableCount=1 -->
<SingleSubst index="0">
<Substitution in="j" out="i"/>
<Substitution in="zero" out="one"/>
</SingleSubst>
</Lookup>
There is one lookup here, but 2 substitutions. My program needs to iterate
through each substitution individually, but the
function hb_ot_layout_lookup_collect_glyphs only returns 2 unordered sets
representing all the input and output characters for this lookup. How can
I get one substitution at a time?
On Tue, Aug 29, 2023 at 3:13 PM Werner LEMBERG <[email protected]> wrote:
>
> > As I was testing my attempt at supporting GSUB lookups, I found that
> > hb_ot_layout_lookup_collect_glyphs, is actually not what I need,
> > because I assumed that each lookup contains exactly one
> > substitution, when it actually may contain multiple. What I really
> > need is a way to get each individual substitution. How do I do
> > this?
>
> It's not completely clear to me what you exactly need, please give an
> example.
>
> Behdad, any idea whether HarfBuzz can help here? Otherwise it is
> probably necessary to parse the GSUB table by ourselves, which is
> something I would like to avoid...
>
>
> Werner
>
