Re: vertical direction control

From: Timothy Partridge (
Date: Wed Mar 24 2004 - 15:17:05 EST

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    Peter Kirk recently said:

    > It seems strangely inconsistent to me that Unicode has detailed controls
    > for horizontal layout direction and the complex bidi algorithm, but has
    > nothing for vertical layout. I can force Latin text to be rendered right
    > to left or Hebrew left to right (although such overrides are hardly
    > plain text issues), but there is no way I can select vertical layout
    > even for languages in which that is a normal way of writing. We already
    > It would be easy to define new characters TOP-TO-BOTTOM EMBEDDING and
    > BOTTOM-TO-TOP EMBEDDING, with similar scope until the next PDF
    > character. The difficult part would be implementing this, and before
    > that defining the exact semantics (but Unicode could define the
    > semantics as beyond its scope). (Another problem would be deciding which
    > variant of mirrored characters e.g. brackets to use given that the
    > context is neither RTL nor LTR - this is a problem with Egyptian
    > hieroglyphs, many of which are mirrored in horizontal text.)

    For Egyptian hieroglyphs the characters generally face towards the start of
    the reading direction. (The occasional one is reversed, and sometimes whole
    texts face the wrong way.) So for horizontal l-to-r t-to-b face left, r-to-l
    t-to-b face right. For vertical t-to-b l-to-r face left, t-to-b r-to-l face
    right. In this case the fact the the inscription is top to bottom doesn't
    help - you need to know what the column arrangement is. You can even have
    both arrangements in one inscription, e.g. on either side of a doorway the
    figures face towards the door. (The bit over the door had the same
    arrangement as one of the sides rather than meeting halfway in the example
    I've seen.) IIRC it's like

    R L
    R L

    Captions next to people in a larger picture usually face in the same
    direction as the person.


    Tim Partridge. Any opinions expressed are mine only and not those of my employer

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