Re: Unicode complaints

From: Mark Davis (
Date: Fri Mar 16 2001 - 10:27:00 EST

That sounds like a promising line. It should certainly be possible to do a
more optimized algorithm for supporting visual look&feel.

(For people that want to try using the reverse bidi algorithm for supporting
things like visual cut&paste and character entry, there is one in ICU.)

----- Original Message -----
From: "Roozbeh Pournader" <>
To: "Unicode List" <>
Cc: "Unicode List" <>; "Behdad Esfahbod"
Sent: Friday, March 16, 2001 06:41
Subject: Re: Unicode complaints

> On Thu, 15 Mar 2001, Mark Davis wrote:
> > There are a huge number of problems in the analysis of text that occur
> > visual ordering; these are avoided with logical ordering, which is why
> > ended up using that for Unicode.
> I know and agree. As I previously told, I am with Unicode in this. I was
> only saying that the current approach of implementors of using only a
> logical buffer, a logical cursor, and a visual to logical position
> translation table in the case their user clicks in the middle of the text,
> is annoying for the general user.
> > Even with logical ordering, one can make the editing process work as
> > you describe. For example, for character input one can make sure that
> > the inserted character appears at the cursor. The key to implementing
> > that is to insert the character at a position where it would show up
> > at the cursor *after* running through the bidi algorithm. A
> > brute-force way to do that is to run the bidi algorithm to get visual
> > order, insert the character, then run it backwards to get the logical
> > order again, which tells you where to put the character. (This is a
> > very rough description -- there are a number of nuances involved, but
> > it can be done.)
> I have thought of that. There are also some other ways that rely on
> the revese bidi algorithm. What I prefer, and am looking forward to find
> the time to implement it, is storing also things like embedding levels
> with text, which means we can have both logical and visual at hand. And
> then trying to have a best guess at when the user wants the character
> lgocially inserted when she presses a key, based on the embedding level
> and the characters at left and right. It also should have some state,
> "entering Indic numbers" or things like that, to help the intelligence.
> --roozbeh

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