Re: Jumping Cursor. Was: Right-to-Left Punctuation Problem

From: Gregg Reynolds (
Date: Tue Aug 02 2005 - 00:08:53 CDT

  • Next message: David Starner: "Re: Jumping Cursor. Was: Right-to-Left Punctuation Problem"

    Kenneth Whistler wrote:

    > And you haven't thought through the consequences of having duplicated
    > digits with different directionality. You might think an end

    Ok, here's an example. Assume that

            123 are LTR, MSD
            xyz are RTL, LSD (1, 2, 3, respectively)

    and that lower case is LTR Latin, and Upper case is RTL Arabic.

    Then "I saw one hundred twenty three elephants" looks like:

    A) LTR context
    display: i saw 123 elephants # LTR within LTR typesetting
    coded text: [i saw 123 elephants] # and MSD polarity

    B) LTR context
    display: i saw xyz elephants # RTL within LTR typesetting
    coded: [i saw zyx elephants] # but LSD polarity - bidi needed

    C) RTL context
    display: STNAHPELE xyz WAS I # RTL within RTL typesetting
    coded: [I SAW zyx ELEPHANTS] # and LSD polarity

    D) RTL context
    display STNAHPELE 123 WAS I # LTR within RTL typsetting
    coded [I SAW 123 ELEPHANTS] # and MSD polarity - bidi needed

    (I tried to construct this using Arabic, but naturally found it
    impossible to mix letters and digits.)

    Obviously cases A and C are the most desirable; no string reversing
    logic required. In each case the typographic semantics result it the
    correct display.

    As for existing software handling the new characters: every Unicode
    character has typesetting semantics - directionality, combining, etc.
    So when a new character comes along, applications that don't understand
    it should not typeset it. Indeed it's a bug if they do, since you can't
    typeset a glpyh if you don't know its typesetting semantics.

    So to me that doesn't look so bad. What am I missing?


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