Ancient history: WHY did ATM and Worldscript II conflict?

Discussion in 'Apple' started by Casey Carter, Jan 22, 2004.

  1. Casey Carter

    Casey Carter Guest

    If anybody out there knows the answer to this, well then my hat's off to
    you, because I've wondered about it for /years/. (Never actually thought
    about asking the ultimate repository of obscure knowledge -- Usenet --
    until 10 minutes ago, though. :-/ )

    Why do Adobe Type Manager and Worldscript II conflict? Everyone knows
    that they *do* -- ATM won't even load, and spits up a dialog box telling
    you as much, if Worldscript II is enabled. But why? Bad programming?
    They patch the same globals? Aliens from Venus stole Adobe's brain and
    replaced it with a wax replica?

    Of course it's entirely moot now that Postscript rendering (and Unicode)
    are rolled into OSX. But I always found it mildly irritating that you
    could have Postscript font smoothing -- OR the Arabic/Hebrew/Indic
    language kits -- but never both at the same time. Very weird. Anyone
    know why?
    Casey Carter, Jan 22, 2004
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  2. Casey Carter

    David Opstad Guest

    Probably something to do with the differences in glyph addressing
    between TrueType and Type 1. WS II made assumptions about specific glyph
    IDs for the Arabic rendering forms (in the low-half of the 256 one-byte
    character codes), and used a "pamc" backwards-mapping table in the FOND
    to allow the font to identify which character code mapped to which
    glyph. (It was called "pamc" because it was the backwards of the "cmap"
    table in the sfnt-housed TrueType fonts. The "cmap" went from character
    code to glyph ID, and the "pamc" went from glyph ID back to character
    code, as I recall).

    The situation was even more baroque for the Indic scripts, where there
    was something called an "associated" font containing the overflow glyphs
    (since 256 character codepoints were insufficient for the minimal
    required set of conjuncts, matras, special half-forms, and so on). This
    all worked in TrueType, because it's easy to obtain a numeric glyph ID
    for any glyph in the font, but because of the way the mapping works in a
    PS font it's much harder there.

    It's all much cleaner now, of course, with Unicode and AAT fully
    supported on all OS X systems. But in its day, WorldScript was a pretty
    amazing thing!

    Dave Opstad
    Line Layout Weenie (ret.)
    David Opstad, Jan 22, 2004
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  3. Casey Carter

    Casey Carter Guest

    Wow! The straight dope, from one who knows. I knew Usenet was the way to
    go. :)

    Thanks for answering a long-held question!
    Casey Carter, Jan 25, 2004
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