Re: Mixed L2R and R2L paragraphs and horizontal scroll

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 31 Jan 2010 21:01:29 +0100
> From: martin rudalics <rudalics@gmx.at>
> CC: emacs-bidi@gnu.org, emacs-devel@gnu.org
> 
>  > In a R2L line, columns should be numbered from the
>  > right margin of the window.
> 
> Technically columns are numbered by counting characters following the
> last newline in the buffer text.

As Miles points out, it's not a simple character counting, but I see
what you mean.

> Just that for R2L text you have to jump to the end of the text first
> and then go back in the text.

Actually, if a R2L line displays text made mostly of strong R
characters (which is normally the case), the first character at the
right margin of the window is also the first character following the
newline in the buffer's logical order.


> So I suppose you're using the term window margin as metaphor here.

Yes, in a sense.  In the displayed portion of the buffer, that is
really the window margin, though.

> 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?

Yes, the truncation for R2L lines will happen at the left, and the
truncation glyph will be displayed there as well.  (It actually
already works like that, at least on a tty.)

>  > And since the columns are numbered from the right margin, hscroll,
>  > too, should scroll R2L lines to the right when L2R lines are hscrolled
>  > to the left.  That's the only reasonable way of generalizing the
>  > current unidirectional hscroll, IMO.  It also preserves the semantics
>  > of window-hscroll (modulo the fact that R2L lines are scrolled from
>  > the right margin, not the left one).
>  >
>  > Makes sense?
> 
> Sounds simple and robust.

Thanks for the feedback.