Re: Need for Level Direction Mark

From: Kent Karlsson <>
Date: Thu, 22 Sep 2011 23:46:10 +0200

Den 2011-09-22 10:54, skrev "Philippe Verdy" <>:

> 2011/9/21 Richard Wordingham <>:
>> LRE...PDF acts like a character with BiDi class L, and likewise for
>> RLE...PDF.  I suppose the principle is that in a right-to-left context a
>> word composed of letters of BiDi class L should be treated like an
>> embedding.
> That's where I think this behavior is wrong. this shoud just set the
> direction to be used internally, hiding this detail to the outside.
> Both sequences should behave like if this was a single character with
> weak Bidi class. Otherwise they are not really "embedding". Even the
> name "pop directional format" is misleading in this case because it
> actually does not restore the state that was before the state pushed
> by LRE/RLE.

I think LRE...PDF (and similarly for the other start bidi bracketings)
should behave as if they had an inherent LDM (LEVEL DIRECTION MARK);
as I have hinted before.

If one changes LRE etc. to have an inherent LDM *functionality*, an
actual character for LDM is not needed, *nor* is a new bidi category
needed. The function of an LDM character can then be achieved by
<LRE, PDF> (or <RLE, PDF>, <LRO, PDF>, or <RLO, PDF>); note: empty
string between the start and end bidi control codes.

I still think there are plenty of other reasons to go for a UBA v.2;
also the change suggested here is probably best done in a UBA v.2
rather than in the current UBA.

    /Kent K
Received on Thu Sep 22 2011 - 16:49:53 CDT

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