Re: Directionality Standard

From: Richard Wordingham (
Date: Sat May 03 2008 - 08:24:15 CDT

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    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,
    (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,

    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.


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