Fwd: Re: selections and combining characters

From: Hubert Figuiere (hub@nyorp.abisource.com)
Date: Thu Apr 25 2002 - 04:35:49 EDT

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    To: Paul Rohr <paul@abisource.com>
    Cc: abiword-dev@abisource.com
    Subject: Re: selections and combining characters
    References: <3.0.5.32.20020422090436.0341acf0@mail.abisource.com>
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    From: Havoc Pennington <hp@redhat.com>
    Date: 24 Apr 2002 22:18:37 -0400
    In-Reply-To: <3.0.5.32.20020423224228.03066100@mail.abisource.com>
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    Paul Rohr <paul@abisource.com> writes:
    > Of the three alternatives described in the Unicode book, I think we've
    > started converging on a rough-but-not-overly-literate consensus that the
    > least preferable option (for us) would be handling atomic character
    > boundaries.
    >

    The Pango is_cursor_position field currently corresponds to
    "graphemes" (see page 126). The text on that page says
    that a grapheme is the logical unit of text and "should behave as
    units in terms of mouse selection, arrow key movement, backspacing,
    and so on."

    In discussion on the list there seemed to be some sentiment that the
    Unicode grapheme algorithm doesn't give exactly the cursor behavior
    that some languages expect, so we allow a language engine to override
    and perhaps modify this.

    There's also some indication (supported by the last paragraph of
    section 5.12) that users want to be able to configure this or
    have it be different in different situations. So we have some idea
    that Pango (and GTK) will support that eventually. This will introduce
    more subtle behaviors into GTK that would need to be synced with a
    custom AbiWord implementation...

    In any case the is_cursor_position field is defined to correspond
    to where you should let people move the cursor, so you could certainly
    just punt the issue to Pango for now.

    To answer your question, I don't remember if the grapheme algorithm
    comes up with "cluster" or "stack" or if it varies by language. In
    any case it avoids the hard one (atomic).

    Havoc

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