From: Richard Wordingham (richard.wordingham@ntlworld.com)
Date: Sat May 03 2008 - 08:24:15 CDT
Otto Stolz wrote on Friday, January 11, 2008 11:12 AM
> Hello Waleed Oransa,
> you have written:
>> What we need is a standard way to encode the directionality of the text
>> that all Unicode-compliant component vendors respect.
> As explained earlier in this thread, you do not have
> to insert such marks “each time”: They are only needed
> in two exceptional cases:
> - if a paragraph starts with an insertion of opposite
> directionality,
> - or when punctuation marks between runs of different
> directionalities belong to the inserted (rather than
> the surrounding) string.
> Whenever a paragraph starts with a string in the paragraph’s
> basic directionality, and contains an insertion in opposite
> directionality, the bidi algorithm will it render as intented.
> This will account for the vast majority of cases.
>
> Only the exceptional cases, as outlined above, will require
> an additional RLM, or LRM, respectively. So the burden on the
> authors is not unreasonably high.
Unfortunately, it's a bit worse than that if a 'higher level protocol
specifies the paragraph level'. The display of <ARABIC LETTER JEEM,
ASTERISK, EXCLAMATION MARK, LATIN SMALL LETTER X> depends on the run level
(Rule N2), which may not be under user control if a 'higher level protocol
specifies the paragraph level', as for example happens in Notepad. Thus, to
be sure of a paragraph consisting of <ASTERISK, EXCLAMATION MARK> displaying
right to left, you need to enter it as <RLM, ASTERISK, EXCLAMATION MARK,
RLM>.
Now, <ASTERISK, EXCLAMATION MARK> is rather an odd string. However,
<ARABIC-INDIC DIGIT 2, ASTERISK> might not be so odd if it is the label on a
trace in a graph, and it has the same display issues.
Richard.
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