Re: about P1 part of BIDI alogrithm

From: Eli Zaretskii <>
Date: Tue, 11 Oct 2011 19:20:06 +0200

> From: Philippe Verdy <>
> Date: Tue, 11 Oct 2011 17:03:51 +0200
> Cc: Kent Karlsson <>, Eli Zaretskii <>,,
> So you'll need to first compute the directionality of all characters
> in a paragraph (where paragraph are broken by strong line breaks
> encoded in the text (or in a upper-level protocol like HTML using "br"
> elements or elements delimiting blocks). Then you'll be able to map
> the mirrored glyphs (ignoring first all the candidate breaks). Then
> only you'll be able to perform the correct substitutions and
> positioning and finally to compute the advance widths that allow to
> determine the position of line breaks. Only then you'll be able to
> reorder the characters within broken lines.

Right. And that means running the UBA, or at least large portions of
it, twice, because computing the directionality means getting at least
as far as after I2 phase. (In addition, it means processing text in
batches, which is entirely against the design of the Emacs display
engine, but that's not a bidi issue.)
Received on Tue Oct 11 2011 - 12:22:47 CDT

This archive was generated by hypermail 2.2.0 : Tue Oct 11 2011 - 12:22:49 CDT