I think this calls for an implementation note on UAX#9 along these lines.
-------------------------
During line breaking, if a line is broken at the location of a SHY, the
text around the line break may change. A common case is the replacement
of the invisible SHY by a visible HYPHEN, but see Section x.x in the
Unicode Standard.
For the purposes of the Bidi Algorithm, apply steps .. to .. after any
substitutions have been made, using the directional classes for the
substituted characters, instead of a single BN for the SHY character.
<example>
Note, no special action need be taken for a SHY character in the middle
of a line, unless they are rendered as visible glyphs in a "show hidden
character" mode. In the latter case, the recommendation would be to
treat the visible symbol substituted for the SHY as having bidi class ON.
------------------------
I am not sure whether -car CBA or car- CBA is the right answer, nor
whether the substitution will always be limited to the preceding line.
(Old orthography German had Bäc<SHY>ker turning in to Bäk-|ker, where
I've used | to show the line ending.) Those are details that the UBA
should be ignorant about. The important thing is that the array of bidi
directional classes is not constrained to contain a single entry for BN
at the location of the original SHY.
If "car- CBA" is the right answer then the substitution would have to be
HYPHEN plus LRM to get this to come out right, but that would be under
the control of the line-breaking conventions, and not legislated by the UBA.
A./
On 4/1/2014 1:31 PM, Whistler, Ken wrote:
Richard Wordingham noted:
> As U+2010 HYPHEN would result in text like 'car-', in an English
> influenced context I would also go with 'car-'.
That's always a possibility, I suppose, but I'm not sure what
"English influenced context" means here.
The examples I just gave were for a RTL paragraph context.
In a LTR paragraph context, the same input would end up in
a very different order:
Trace: Entering br_UBA_ReverseLevels [L2]
Current State: 19
Text: 05D0 05D1 05D2 0020 0063 0061 0072 002D
Bidi_Class: R R R L L L L L
Levels: 1 1 1 0 0 0 0 0
Runs: <L-----------------------------------L>
Order: [2 1 0 3 4 5 6 7]
And you get the display:
CBA car-
--------->
As opposed to:
-car CBA
<---------
In either case, the hyphen-minus (or hyphen), ends up at the *end of
the line*.
My take is that *if* I am going to insert a visible glyph at the point
of the
SHY, it would probably be best to insert it at the actual line break
at the
end of the line, to be in the same position as an explicit
hyphen-minus with
the same line break.
--Ken
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