Re: `C-b' is backward-char, `left' is left-char - why?

[David Kastrup <dak@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: David Kastrup <dak@gnu.org>
>> Date: Sun, 05 Jun 2011 19:26:58 +0200
>> 
>> However, there is no reason that straight visual movement when using
>> shift-selection would interfere with selection as such: you just can't
>> expect that the marked region is visually contiguous.  The size of the
>> selection will jump when crossing visually from L2R and R2L.
>> 
>> But I see no logical problem with that.
>
> The problems with this are not logical, they are with implementing it
> (both the movement itself and the resulting selection and highlight).
> Patches are welcome.

The resulting selection and highlight appear to do just what is needed
already and don't seem to have a problem with visual discontinuity.

So only the movement itself would appear to be an issue.

If one has text like

llllllllRRRRRRRRllllll

there is a difference between the cursor being just to the right of the
first lll passage (namely before all of the RRR), and being just to the
left of the RRR passage (namely after all of the RRR).  Since being just
to the left of the RRR passage is the same point position as being just
to the left of the second lll passage, the effect of shift-marking while
moving left (let's reserve uppercase now for the marked passage) would
flip:

llllllllrrrrRrrrllllll
llllllllrrrRRrrrllllll
llllllllrrRRRrrrllllll
llllllllrRRRRrrrllllll
llllllllRRRRRrrrllllll
lllllllLrrrrrRRRllllll

Actually, I've just tried entering mixed L2R and R2L stuff with the
keyboard and bidi-display-reordering set, and I find it quite
distracting that the insertion point for "reversed" text (with regard to
the current paragraph direction) gets increasingly distant from the
cursor itself.

-- 
David Kastrup