Re: Vertical BIDI

From: John Cowan (
Date: Tue May 18 2004 - 21:54:47 CDT

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    Philippe Verdy scripsit:

    > This creates an interesting problem: Put in the same sentence Han
    > (Chinese) and Mongolian words in a vertical layout (I don't think this
    > is unlikely, as Mongolian is also spoken in China, and there's also
    > a Chinese community in Mongolia). So Chinese ideographs will be laid
    > out vertically from top to bottom (but not rotated, except for a few
    > characters like ideographic punctuation marks or symbols), and Mongolian
    > will be laid out from bottom to top in their normal stack orientation.

    In fact no; both Mongolian (or Manchu, which is unified with it in
    Unicode) and Chinese are written TTB. When Mongolian stands alone, the
    columns progress from left to right, but when it's mixed with Han, the
    columns progress from right to left, as is the case with Chinese alone.
    Presumably this is about like writing a Latin-script language with upright
    glyphs and LTR, but progressing from the bottom of the page to the top:
    annoying but legible.

    > Now admit that you want to present it horizontally: Han ideographs will
    > not be rotated but will flow on rows from left to right. Suppose you
    > have performed the Bidi processing according to the previous vertical
    > presentation, then Mongolian stacks will flow from right to left
    > (but unlike Han ideographs, they will need to be rotated...)

    You don't. Horizontal Mongolian runs left to right, which means that
    with respect to its Aramaic ancestor the glyphs are upside down.

    Now when mixing Ogham vertical text with other vertical scripts, you
    do indeed need to use RLO ... PDF to force it into bidirectional
    behavior, but it's the only such case.

    There seem to be two different alternatives for RTL horizontal alphabets
    in a vertical context, depending on which way the glyphs are rotated.

    But you, Wormtongue, you have done what you could for your true master.  Some
    reward you have earned at least.  Yet Saruman is apt to overlook his bargains.
    I should advise you to go quickly and remind him, lest he forget your faithful
    service.  --Gandalf             John Cowan <>

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