Re: [emacs-bidi] status? news?

[Behdad Esfahbod]

On Mon, 5 Feb 2001, Eli Zaretskii wrote:

>
> On Mon, 5 Feb 2001, Behdad Esfahbod wrote:
>
> > On Mon, 5 Feb 2001, Eli Zaretskii wrote:
> >
> > > > Date: Sun, 21 Jan 2001 17:37:21 +0330 (IRT)
> > > > From: Roozbeh Pournader <address@hidden>
> > > >
> > > > On Sun, 21 Jan 2001, Eli Zaretskii wrote:
> > > >
> > > > > Could you please elaborate on these problems with next text lines?
> > > >
> > > > With implicit bidi support (with LRM and RLM, but without LRE, RLE,
> > > > LRO, RLO, and PDF), you can first break the lines, and then apply bidi 
> > > > to
> > > > each line separately for reordering before the display.
> > > >
> > > > With explicit support, you should first do bidi on the whole paragraph,
> > > > then break the lines, and finally reorder the text. This is considered
> > > > hard to do in many applications.
> > >
> > > Nevertheless, the Unicode algorithm specifically says that
> > > line-breaking should happen _before_ reordering.  Is that a bug in
> > > UTR9?
> >
> > I Don't think so, in the "Reordering Resolved Levels" of UTR9 it says:
> > "
> > Logically there are the following steps:
> > ...
> > o  the accumulated widths of those glyphs (in logical order) are used
> >    to determine line breaks.
> > o  for each line, rules L1-L4 are used to reorder the characters on
> >    that line.
> > ...
> > "
>
> Precisely!  This says that you determine line breaks by accumulating the
> glyph widths _in_logical_order_, and only after that reorder the
> characters on each line into the visual order.
>
> This seems to contradict what Roozbeh said in the message to which I
> replied, see the quotations above.
>
> Am I missing something?
>

I have discussed this too much with Roozbeh, as both of us agree, You
must do in this order:
1 calculate the embedding levels (roozbeh called "apply bidi"),
2 select the proper glyphs,
3 break lines,
4 reorder

you cannot break lines before calculating the embedding levels,
because explicit marks may affect the glyph selecting phase.