[alreq] Vertical text handling in Unicode

r12a has just created a new issue for https://github.com/w3c/alreq:

== Vertical text handling in Unicode ==
This is brought here from https://github.com/w3c/alreq/issues/102

@behnam wrote

Continuing the discussion on behavior in vertical lines...

>From http://www.unicode.org/reports/tr9/#Vertical_Text

> In the case of vertical line orientation, the Bidirectional Algorithm is still used to determine the levels of the text. However, these levels are not used to reorder the text, because the characters are usually ordered uniformly from top to bottom. Instead, the levels are used to determine the rotation of the text. Sometimes vertical lines follow a vertical baseline in which each character is oriented as normal (with no rotation), with characters ordered from top to bottom whether they are Hebrew, numbers, or Latin. When setting text using the Arabic script in vertical lines, it is more common to employ a horizontal baseline that is rotated by 90° counterclockwise so that the characters are ordered from top to bottom. Latin text and numbers may be rotated 90° clockwise so that the characters are also ordered from top to bottom.
> 
> The Bidirectional Algorithm is used when some characters are ordered from bottom to top. For example, this happens with a mixture of Arabic and Latin glyphs when all the glyphs are rotated uniformly 90° clockwise. The Unicode Standard does not specify whether text is presented horizontally or vertically, or whether text is rotated. That is left up to higher-level protocols.

Therefore, Unicode recommends here that when there's only one text (strong chars only) direction, the Arabic should be written top-to-bottom, so glyph rotations should be 90º CCW. This contradicts the behavior recommended by latest CSS specs, and what we have in the document at the moment.

What do you think?

Please view or discuss this issue at https://github.com/w3c/alreq/issues/140 using your GitHub account

Received on Tuesday, 12 September 2017 15:30:05 UTC