[HarfBuzz] bug in hb_ot_layout_lookup_collect_glyphs?

[Werner LEMBERG]

Behdad,


HarfBuzz doesn't validate glyph indices returned by
`hb_ot_layout_lookup_collect_glyphs'.  I think this qualifies as a
bug.

The attached font incorrectly uses glyph index 0xFFFF in a GSUB
lookup.  ttx says

  <GSUB>
    ...
    <LookupList>
      <!-- LookupCount=8 -->   
      <Lookup index="0">
        <LookupType value="1"/>
        <LookupFlag value="0"/>   
        <!-- SubTableCount=1 -->
        <SingleSubst index="0" Format="2">
          ...
          <Substitution in="uni0162" out="glyph65535"/>  
          <Substitution in="uni0163" out="glyph65535"/>  

and HarfBuzz happily returns 0xFFFF, too.


    Werner
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