Re: Mixed L2R and R2L paragraphs and horizontal scroll

[tomas]

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On Tue, Feb 02, 2010 at 09:08:16AM +0100, martin rudalics wrote:
> >     There is one thing I conceptually don't understand yet: When I 
> currently
> >     shrink the width of a window Emacs doesn't hide text at the left side 
> of
> >     the window but text at the right side may get truncated when the 
> window
> >     becomes too small.  Will this behavior be reverted for R2L text in 
> the
> >     sense that text at the left side is truncated?
> >
> > Since R2L text lines start from the right margin, that will remain
> > true after changes in window width.  This is true independent of how
> > hscroll works.
>
> With L2R and R2L lines in one and the same buffer we have to decide
> which line type is given preference whenever shrinking a window
> truncates at least one L2R and at least one R2L line.

(AFAIU) not if you follow Eli's approach of "moving from center" (i.e.
anchor R2L lines right and L2R lines left (which looks as the most
compelling approach to me [1]). That would be "inverted scrolling" in
Stefan's classification in this thread.

There seem to be some limitations to this model, like what to do when
L2R and R2L mix in a line (especially in structured lines, like table
rows, cf. Ehud's post in this thread).

> preference" here means which line type is allowed to place its first
> column at the respective window margin.  Usually, the preferred line
> type can be derived from the position of `point'.  For example, when
> `point' is at the beginning of a R2L line it's appropriate to show the
> right margin when shrinking the associated window.

It seems to me that you'd prefer to keep R2L and L2R texts rigidly tied
(column-wise), if i understand you correctly (i.e. Stefan's "rigid
scrolling"). But I don't know whether this is well-defined without
pre-supposing some arbitrary text with to begin with (and what do you do
with proportional fonts? Ligatures?).

Regards

[1] Disclaimer: I do follow those bidi discussions, but my headd spins
so fast that I don't think my judgements are very valid at the moment.

- -- tomás
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