Re: [emacs-bidi] Mixed L2R and R2L paragraphs and horizontal scroll

[Ehud Karni]

On Sat, 30 Jan 2010 15:44:28 Eli Zaretskii wrote:
>
> Here's a peculiar design decision that needs to be made for the bidi
> display: how to display horizontally scrolled lines in a buffer with
> mixed L2R and R2L paragraphs.
>
> Let me start with an example of 2 single-line paragraphs (the frame
> around the text shows the window borders):
>
>       +---------------------------------------+
>       |abcdefghijk                            |
>       |                            KJIHGFEDCBA|
>       |                                       |
>       +---------------------------------------+

[sniped]  Eli's final conclusion for scrolled text is:

>       +---------+---------+-------------------+
>       |$ijk     |abcdefgh$|abcdefghijk        |
>       |     KJI$|$HGFEDCBA|        KJIHGFEDCBA|
>       |         |         |                   |
>       +---------+---------+-------------------+

I agree with Eli's decision, but it applies only to non-technical text.

Consider Example1: a list of items, each line has: name, quantity,
catalog-id and description. Most of the names are in Latin but some
are in Hebrew.
In this case there must be an external dictation of paragraph direction.

Example 2: same list as above, all the names are in Latin, the
description is very long, some of the descriptions are in Hebrew.
       +----------------------------------------+
       |name1 1234 catag1 very-long-description |
       |name2 1234 catag2 NOITPIRCSED-GNOL-YREV |
       +----------------------------------------+
and in a smaller window:
       +-------------------------------+
       |name1 1234 catag1 very-long-de$|
       |name2 1234 catag2 ED-GNOL-YREV$|
       +-------------------------------+
scrolled (5) in a smaller window:
       +-------------------------------+
       |$1234 catag1 very-long-descrip$|
       |$1234 catag2 PIRCSED-GNOL-YREV$|
       +--------------------------------
scrolled (23) in a smaller window:
       +-------------------------------+
       |$ong-description               |
       |$NOITPIRCSED-GNO               |
       +--------------------------------

Example 3: text, mostly in Hebrew but some lines have no Hebrew,
like arithmetic formulas (Latin + digits + neutrals only) or
ls output (real recent email I got).

Here we could use either external dictation of RTL direction or
automatic paragraph direction. In RTL direction the formula may be
displayed wrongly (if neutral characters are on the sides). When
automatic paragraph direction is used, short lines may be too far
apart. In this case, something like `right-margin-goal-column' as
suggested by RMS is a good solution.

Ehud.


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