From: Ted Hopp (firstname.lastname@example.org)
Date: Thu Oct 09 2003 - 07:45:21 CST
One issue with deleting a DGC non-atomically is that deleting only the base
character can lead to all sorts of strange and problematic combining
character sequences. At a minimum, deleting a base character should delete
the entire DGC atomically. In Hebrew, I don't see any problem with deleting
combining characters non-atomically (although one might want to limit this
to just off the logical end of the sequence out of user interface
considerations). I suppose that this might be more of an issue in some other
One might be tempted to use some sort of canonical ordering logic to keep
the complexity down, but the combining classes for Hebrew are so problematic
that this would be a lost cause.
I have used software where the cursor moves non-atomically across a DGC in
Hebrew and I find it extremely confusing. The only way to make sense of
what's happening is to remember the exact sequence in which the combining
characters were entered. If someone wants to support such movement anyway, I
think that the cursor shape needs to change dramatically to indicate what's
going on. This is something I've never seen done well (usually not at all).
Subtle changes in cursor position are useless as a visual indication to the
user of what's going on. One might even need to include some sort of glyph
highlighting to make clear the state of the text entry system.
Ted Hopp, Ph.D.
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