Re: about P1 part of BIDI alogrithm

From: Kent Karlsson <>
Date: Tue, 11 Oct 2011 12:39:57 +0200

Den 2011-10-11 09:43, skrev "Eli Zaretskii" <>:

> Let me give you just one example: if the character should be mirrored,
> you cannot decide whether it fits the display line until _after_ you
> know what its mirrored glyph looks like. But mirroring is only
> resolved at a very late stage of reordering, so if you want to reorder
> _after_ breaking into display lines, you will have to back up and
> reconsider that decision after reordering, which will slow you down.

Well, I think there is a silent (but reasonable, I would say) assumption
that mirroring does not change the width of a glyph... I would think that if
a font does not fulfill that, then you have a font problem (or mix of fonts
problem), not a bidi problem. Glyphs for characters that may mirror do not
normally form ligatures with other glyphs; and even if they do, the width of
the ligature should not change relative to the total with of the preligature
glyphs involving glyphs for mirrorable characters (and if it does change
anyway, you again have a font problem that may result in a somewhat ugly
display that should be fixed by fixing the font, not a bidi problem). I'm
not thinking about Emacs here, but in general.

    /Kent K
Received on Tue Oct 11 2011 - 05:45:04 CDT

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