L2/04-168

Date: 2004-05-24 12:31:41 -0700
Subject: Bidi Errata
Source: Behdad Esfahbod

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Subject:  Default bidi types for reserved and non-character slots

The default property values for Bidi_class in UCD.html lacks default
BN entries, which by exploring DerivedBidiClass.txt I've found to be
these:

2060..206F
FDD0..FDEF
FFF0..FFF8
E0000..E0FFF

FFFE..FFFF
1FFFE..1FFFF
2FFFE..2FFFF
3FFFE..3FFFF
4FFFE..4FFFF
5FFFE..5FFFF
6FFFE..6FFFF
7FFFE..7FFFF
8FFFE..8FFFF
9FFFE..9FFFF
AFFFE..AFFFF
BFFFE..BFFFF
CFFFE..CFFFF
DFFFE..DFFFF
EFFFE..EFFFF
FFFFE..FFFFF
10FFFE..10FFFF

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Subject:  Directional run in UAX#9

The relatively new section on Shaping in UAX#9 reads:

"Shaping is logically applied after the bidirectional algorithm
is used, and limited to characters within the same directional
run."

But a "directional run" is not defined in the document.  In BD7 a
"level run" is defined as "a maximal substring of characters that
have the same embedding level."

So the immediate defition for "direction run" that comes to my mind
is "a maximal substring of characters that have the same
embedding level parity (all odd or all even)." which makes sense
in the context it's used.  It should probably be documented somewhere
in that document.

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