Re: Implement BIDI algorithm by line

From: li bo <libo.imc_at_gmail.com>
Date: Tue, 23 Aug 2011 10:02:05 +0800

 Yes, this is the algorithm I have read. http://unicode.org/reports/tr9/
But I don't know why user must take a paragraph as a unit to determine the
embedding levels. Why can't i shape the text first and then wrapping the
line, and determining the embedding levels for characters within a line.
finally, reordering the characters within a line.
If a paragraph is too long, i think it's a big memory occupied. This would
be a limite in embedding system such as mobile phone.
On Tue, Aug 23, 2011 at 2:18 AM, CE Whitehead <cewcathar_at_hotmail.com> wrote:

> Hi.
>
> I think many line breaks within paragraphs are soft line breaks but that
> embedding levels have to be taken into account when deciding the width of
> the glyphs; that's as near as I can tell.
>
> Here is the description of the algorithm -- is this what you have read?
> http://unicode.org/reports/tr9/
> Some rules are in fact applied after the line wrapping (after the soft
> breaks) --
> "The following rules describe the logical process of finding the correct
> display order. As opposed to resolution phases, these rules act on a
> per-line basis* and are applied after any line wrapping is applied to the
> paragraph.*
> Logically there are the following steps:
>
> - The levels of the text are determined according to the previous
> rules.
> - The characters are shaped into glyphs according to their context *(taking
> the embedding levels into account for mirroring).*
> - The accumulated widths of those glyphs *(in logical order)* are used
> to determine line breaks.
> - For each line, rules L1 <http://unicode.org/reports/tr9/#L1>L4<http://unicode.org/reports/tr9/#L4>are used to reorder the characters on that line."
>
>
>
> (I'd have to reread the whole document on line breaking then on bidi to
> answer this truely; sorry; hope this helps anyway)
> --C. E. Whitehead
> cewcathar_at_hotmail.com
>
Received on Mon Aug 22 2011 - 21:06:40 CDT

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