Re: Directionality Standard

From: Behnam (
Date: Fri Dec 21 2007 - 17:32:08 CST

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    I do not expect all applications support rtl. Because unfortunately I
    am realistic. What I do expect though, is that my rtl paragraph,
    going to an application that doesn't support rtl, and then from that
    application to yet again another application which does support rtl,
    reappear in rtl. The same way that the encoded text reappears intact.
    This is what Unicode should ensure that it happens as it does for the
    characters themselves.

    I also believe that different formats and mediums should solve their
    technical problems without interfering with directionality encoded in
    a text.

    I'm amazed that Unicode has put so much effort in implementing bidi
    algorithm to so many characters, and so little, to keep it useful.


    On 20-Dec-07, at 11:48 AM, Jony Rosenne wrote:

    > The difficulty with invisible marks is that they are not visible
    > and thus
    > are easily overlooked.
    > Jony
    > -----Original Message-----
    > From: [mailto:unicode-
    >] On
    > Behalf Of Asmus Freytag
    > Sent: Thursday, December 20, 2007 10:31 AM
    > To: Kent Karlsson
    > Cc: 'Stephane Bortzmeyer'; 'Behnam';
    > Subject: Re: Directionality Standard
    > Kent,
    > adding a LRM or RLM at the head of the paragraph allows the Unicode
    > text
    > itself to carry an indication of the desired top-level directionality.
    > That indication will be picked up by any implementation of the
    > *default*
    > algorithm (but is easily overridden by any external markup in
    > protocols
    > that support it.). The way it works, is that the mark counts as a
    > letter
    > with strong directionality, in this case the first strong letter used
    > for setting the top-level directionality, while being otherwise
    > invisible in the display.
    > A./
    > On 12/19/2007 3:02 PM, Kent Karlsson wrote:
    >> Stephane Bortzmeyer wrote:
    >>>> Can't a Hebrew site have a news in Hebrew, with a long quotation of
    >>>> the speech of an American politician in English in an ltr
    >>>> paragraph?
    >>> Yes, and Unicode handles it fine, in plain text, without the need
    >>> for
    >>> support from a markup language (because each Unicode character has a
    >>> direction).
    >> No, that's not the issue. The display of a line of bidi text (with
    >> actual mix of directions) becomes completely different depending on
    >> the top level paragraph direction. That is NOT derived from "each
    >> Unicode character has a direction" (considering just those that
    >> have strong directionality).
    >> The initial poster in this thread gave a good example. But here is a
    >> simpler one, using the convention that uppercase denotes RTL letters.
    >> The *same* input text, logical order "ABCdefGHI", gets the display
    >> CBAdefIHG if the top level direction is LTR (a.k.a. level 0)
    >> IHGdefCBA if the top level direction is RTL (a.k.a. level 1)
    >> The top level paragraph direction is not inherent in the text (and
    >> *cannot* be), though the bidi algorithm specifies a default, but just
    >> a default, usually overriden by markup (or language tag) when markup
    >> (or language tag) is available, since the default is not stable for
    >> editing (unless the editor forces the use of a LRM or RLM char at the
    >> beginning of each paragraph).
    >> /kent k

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