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    • OT Sub Prioritisation (Need Help)

    Posts: 12
    in Type Design Software
    I'm working on a monospaced, and playing around with ligatures for i_i, i_l, l_i, and l_l.

    I'm trying to set it up so that the sequence i l l becomes i l_l, not i_l l.

    The ordering of my substitution rules for i_l and l_l doesn't make a difference and nothing else I can think of or find online helps either.

    Thanks in advance.
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    Comments

    • Posts: 243
      set the first line of your feature to:
      sub i l' l' by l_l;
      The order of the substution rules does matter, and you need to define the longest substitutions first.
    • Posts: 3,355
      Try putting the l_l substitution in a separate lookup before the i_l lookup.
    • Posts: 12
      Thanks @Paul van der Laan, that did it.

      Thanks, too, @John Hudson.
    • Posts: 979
      and you need to define the longest substitutions first.
      Actually, this is not strictly true for features in Adobe syntax which are being compiled by AFDKO. From http://www.adobe.com/devnet/opentype/afdko/topic_feature_file_syntax.html#5.d :

      “A contiguous set of ligature rules does not need to be ordered in any particular way by the font editor; the implementation software must do the appropriate sorting.”

      The compiler is supposed to be responsible for ordering the longest substitutions first.
    • Posts: 3,355
      In this case, though, the substitutions are of equal length:

       i l -> i_l
       l l -> l_l

      Paul has suggested a way to handle this by making the substitution for the sequence <i l l> to /i l_l/ contextual. That's certainly one solution.

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