Re: selections and combining characters

From: Andrew Dunbar (hippietrail@yahoo.com)
Date: Mon Apr 22 2002 - 23:44:06 EDT

  • Next message: Andrew Dunbar: "Re: undo and combining characters"

     --- Paul Rohr <paul@abisource.com> wrote: > At 09:30
    PM 4/22/02 +0200, Karl Ove Hufthammer
    > wrote:
    > >Paul Rohr <paul@abisource.com> wrote in
    >
    >news:3.0.5.32.20020422090436.0341acf0@mail.abisource.com:
    > >
    > >> How should selections work for combining
    > characters?
    > >
    > >See chapter 5.12 of the Unicode book, available
    > online at
    > ><URL:
    > http://www.unicode.org/unicode/uni2book/ch05.pdf >.
    >
    > Thanks for the excellent reference, Karl.
    >
    > My question remains, but now the possible answers
    > can be far more precisely
    > defined. Specifically:
    >
    > 1. Which level of consistent character boundaries
    > Just Works?
    >
    --------------------------------------------------------------
    > In the vocabulary of 5.12 here, the choices are:
    >
    > - Cluster Boundaries
    > - Stacked Boundaries
    > - Atomic Character Boundaries

    I'd vote for Stacked Boundaries first. Cluster
    boundaries seem to make sense for scripts that the
    user doesn't understand. Atomic Boundaries might be
    added at some stage as part of adding this RFE:
    http://bugzilla.abisource.com/show_bug.cgi?id=1441
    But this would be a very low priority IMHO.

    > Since AbiWord is designed to allow easy entry,
    > manipulation, and formatting
    > of large quantities of text, I'd think we should
    > rule out the third option.
    > It might make re-entry of portions of a composed
    > character easier, but it
    > opens up a rat's nest of formatting issues in the
    > UI.

    Agreed. But maybe add it some day.

    > As for the other two, I'm not a native speaker of
    > Devangari, but I'm willing
    > to guess that cluster selection would be preferred
    > behavior for them. For
    > example, is it ever meaningful to make *part* of the
    > "ka + vowel sign a"
    > cluster bold?

    Yes because they are typed as seperate characters.
    They are never typed combined.
    It might make sense when editing a multilingual
    document containing scripts you don't understand but
    is this likely to occur?

    > OK, now I'll duck while the native speakers set me
    > straight. :-)

    Oh and Devanagari isn't a language, it's a script
    which
    is used to write Hindi, Nepali, Sanskrit, and Marathi.

    > 2. Which selection mode Just Works for bidi text?
    > --------------------------------------------------
    > According to section 3.1.3 of one of Karl's other
    > references:
    >
    >
    >
    http://www.w3.org/TR/charmod/#sec-VisualRenderingUnits
    >
    > there are two possible selection modes for BiDi
    > text:
    >
    > - logical selection mode
    > - visual selection mode

    Only logical makes sense really. Even though it
    looks confusing to non-RTL language users, it makes
    sense. Visual would mean you actually select *two*
    parts of your document! No clipboard format can
    handle multiple parts - and what would it mean to
    paste them anyway?

    > As one of the parties responsible for the selection
    > code Tomas inherited,
    > I'd guess he may have found it easier to implement
    > the logical mode, but I
    > wasn't paying enough attention when that got
    > implemented.

    I haven't been able to test it ):

    > Is the other mode more desirable? If so, how bad
    > would it be to encapsulate
    > the necessary selection logic to allow discontiguous
    > selections?

    I honestly can't see a use for it. English speakers
    may at first think this one makes sense but it
    doesn't.

    Andrew Dunbar.

    > Paul

    =====
    http://linguaphile.sourceforge.net http://www.abisource.com

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