RE: Generic base characters

From: Peter Constable (
Date: Sun Jul 15 2007 - 14:53:57 CDT

  • Next message: Sinnathurai Srivas: "Re: Generic base characters"

    It's not entirely clear to me what you want. If you want a vowel mark to appear in isolation without any visible base, then use U+00A0 NO-BREAK SPACE as the base.


    -----Original Message-----
    From: Sinnathurai Srivas []
    Sent: Sunday, July 15, 2007 1:19 AM
    To: Peter Constable; Unicode List
    Subject: Re: Generic base characters

    The principle behind dotted circle is very problem some.
    One does not always need a base character when writing.
    I know in Tamil longer than long vowels and longer than long dipthongs are
    reality and it is part of Grammar. But Unicode defines it differently. So it
    is not a problem with Microsoft, but a problem with Unicode definition. I
    think we need to find a way to either remove the ristrictions placed by
    dotted circle or find other technical solution for this problem
    Words line
    Auai, varuuum etc are in use.

    Is this proposition to remove dotted circle possible?


    ----- Original Message -----
    From: "Peter Constable" <>
    To: "Unicode List" <>
    Sent: 15 July 2007 06:14
    Subject: RE: Generic base characters

    > From: [] On
    > Behalf Of Christopher Fynn
    >> The Microsoft OpenType shaping engine, Uniscribe, seems to
    >> automatically insert a dotted circle as a base character
    >> for isolated combining marks - and this behavior is outside
    >> of the control of the font developer.
    >> IMO it would be much better if font developers were
    >> responsible for defining their own sets of these base glyphs
    >> for combining marks - including the base for isolated
    >> combining marks - and their own lookups for rendering the
    >> resulting combinations.
    > Uniscribe inserts a dotted circle glyph only when the author has not
    > included a valid base character for the mark. Font developers are always
    > responsible for their own lookups for rendering a mark glyph on a base.
    > But there's nothing the font developer can do about the scenario in which
    > an author fails to include a base.
    > Perhaps you have in mind that a font developer should control what glyph
    > is used in that situation, but I see a need, on the assumption that
    > authors should, and normally are, explicitly intentional about what is in
    > their document, and that Uniscribe's fallback rendering is just that: a
    > fallback.
    >> As base glyphs one might want to include the dotted circle;
    >> non-breaking space or fixed width spaces such as em space or
    >> en space;
    > Unicode specifies that combining marks in isolation -- with no visible
    > base -- should be combined with NO-BREAK SPACE, not any of the other space
    > characters in the standard.
    >> Right now if I have a lookup in an OpenType font to place
    >> an isolated mark on the dotted circle Uniscribe also inserts
    >> dotted circle and I end up getting two doted circles...
    >> Not all OpenType shaping engines exhibhit this behaviour.
    > A bug, which can be looked at.
    > Peter

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