Re: Hl-line and visual-line

[Eli Zaretskii <eliz@gnu.org>]

> From: David Reitter <david.reitter@gmail.com>
> Date: Sun, 23 May 2010 15:13:42 -0400
> Cc: tassilo@member.fsf.org,
>  emacs-devel@gnu.org
> 
> The first use case would be to jump to beginning and end of a visual line.  That means, if point is at any of {abcde JIHGF}, beginning would be at "a" and the end at " " (between "E " and "F").
> If point is at any of {ABCDE xyz}, then beginning would be at "E" and end would be after "z".

This already works today, so no change seems to be needed to cover
this.

> C-k (kill-visual-line) would probably need to be rewritten anyway.

Why? it seems to work already, killing the visual line.  Am I missing
something?

> The second use case would be to actually capture a whole line.  I have functions that kill the whole line (from left to right).   They would use `kill-region' from X to Y.   The same goes for hl-line-mode, where ONE overlay is drawn.
> So, these functions would need a new function such as "regions-within-visual-line" or so, returning a list of (from . to) regions, or some other means of identifying the region. 

Sorry, I don't get this part.  Can you give an example that uses
kill-region and another one with one overlay for hl-line-mode, and
explain how the list of the form you mention would help?

> Are we going to have discontinuous regions?  When I set the Mark at "c" in your example, and point at "G", what is highlighted (transient-mark-mode), and what is killed?

Both the region and kill commands work in logical order.  So after
C-w, you will see

  ab JIHG xyz

I don't think we should have discontinuous regions.  Their semantics
is not clear (there's more than one way of interpreting them), and no
bidi-aware application I've seen supports them.

Users expect logical-order regions.  Logical-order regions may surprise
the first time you see it, but are easy to get used to, since that's
the order you read the text you mark.

> (NB You're throwing some of the most basic assumptions away.   This could get interesting.)

Yes, I'm in this "interesting" stuff for several months now.