Re: 3 big bidi bugs

From: Timothy Partridge (timpart@perdix.demon.co.uk)
Date: Wed May 29 2002 - 15:42:34 EDT


Bernard Miller recently said:

> This can be fixed by rewording step L2 such that a reversal happens from the
> highest embedding level to each lower contiguous embedding level, regardless
> if the embedding level is represented by a character on the line, until the
> embedding level of 1 is reached (or, as an optimization, until the first odd
> embedding level equal to or lower than the lowest embedding level
> represented by a character on the line).

I had always interpreted L2 in the manner of your suggested correction, but
perhaps the language could be clarified.

> (2) Line width dependent mangling, spelling conventions for quotes:
> What is the purpose of step X10 if not to allow something like LEFT DOUBLE
> QUOTATION MARK to be used as if it was an OPEN DOUBLE QUOTATION MARK? One
> simply puts an embedding inside a quotation, such as <RLE>quotation<PDF>.

Surely if the quotation is meant to be right to left the RLE and PDF should
be outside the entire thing, including the quotes. After all the intention
is for the quotes to match the text is it not?

> (3) Mirroring ambiguities:
> What if eor = sor?

> text: R RLO whatever PDF N LRO whatever PDF
> embedding level at step X9: 1 3 3 1 2 2
> directional type at step X10: R R R ? L L

Have you perhaps misunderstood <sor> and <eor>? They are imaginary things
inserted at the run boundaries, not a role undertaken by an actual character
inside the run.

For the above I make them as follows:

> text: R RLO whatever PDF N LRO whatever PDF
> embedding level at step X9: 1 3 3 1 2 2
                               <s> <e><s> <e><s> <e><s> <e>
> directional type at step X10: R R R R R R R R ? L L L L L

In particular at the start of the level 1 run in the middle the highest
level on either side of the boundary is 3 so the direction of the <sor> (and
the preceding <eor>) is R. At the end of the run the highest level is 2 so
the <eor> is L as is that of the following <sor>.

The Neutral has a conflict of directions surrounding it so it takes the
embedding direction which is R.

   Tim

-- 
Tim Partridge. Any opinions expressed are mine only and not those of my employer



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