On Thu, 13 May 2004 16:33:51 -0400, [EMAIL PROTECTED] wrote: > > That's irrelevant. L2R and R2L scripts are often mixed in the same > sentence, whereas it's barely possible to mix horizontal and vertical > scripts on the same page; when it must be done, the vertical script > is generally rotated to become a L2R horizontal one (even Mongolian). > A page that contained both Mongolian and vertical CJK might require > a vertical bidirectional algorithm, but AFAIK that question has not > yet arisen.
I'm a little confused by the last sentence. Mongolian and traditional Chinese are both written vertically from top to bottom, and so a vertical bidirectional algorithm is not relevant. Mixed Chinese/Mongolian and Chinese/Manchu texts are extremely common. Traditionally vertical layout of mixed Mongolian/Chinese text is preferred, but in modern Chinese books that have individual Mongolian words and phrases embedded in Chinese text then horizontal layout is common (with any complete passages of Mongolian text usually typeset vertically on a separate page). Where Mongolian and Chinese do differ is that traditional Chinese is written in vertical columns from right to left across the page, whereas Mongolian and Manchu are written in vertical columns from left to right across the page (because the Uighur script from which Mongolian derives is actually a rotated RTL script). In bilingual Manchu-Chinese texts, which were common during the Manchu Qing dynasty [1644-1911], the text normally follows the Manchu page layout, with vertical lines of Manchu and Chinese interleaved from left to right across the page, so that from a Chinese perspective the book reads backwards. As I suggested in a recent thread on mixed horizontal/vertical layout, if you did have mixed Top-To-Bottom (TTB) and Bottom-To-Top (BTT) scripts such as Mongolian and Ogham (not that Ogham's strictly BTT, but it is largely BTT in monumental inscriptions -- although for convenience it is almost always written LTR on paper and on screen ... and even in the Unicode code charts), then you could deal with their conflicting directionality as if they were rotated LTR and RTL scripts by means of LRO, RLO and PDF control codes [202C..202D]. Peter and Ken's remarks in this thread seem to suggest that this interpretation is correct, and that the terms "Left-to-Right" and "Right-to-Left" are relative directions not absolute directions with respect to plain text layout. A plain text editor would normally lay out vertical text such as Mongolian horizontally whether you like it or not; but if there were a plain text editor that laid everything out vertically then presumably the bidi algorithm and bidi control characters would not be invalidated simply because mixed LTR and RTL text were laid out in vertical lines rather than horizontal lines. As has been stated time and time again, mixing vertical and horizontal textual orientation in the same document is beyond the scope of a plain text standard, and rendering mixed horizontal/vertical text is certainly beyond the ability of any plain text editor that I know of. Markup is the appropriate way to deal with mixed horizontal/vertical/diagonal/circular/spiral text (Artemis Fowl has a constructed "script" with spiral textual orientation), not dozens of new directional control characters. Andrew
