bug#16148: Cursor stuck on line ending w/ visual-order-cursor movement - move-point-visually fails.

bug#16148: Cursor stuck on line ending w/ visual-order-cursor movement - move-point-visually fails.

[David Reitter]

With a certain combination of settings, cursor movement to the left fails at the (right) end of lines:

Emacs -Q -nw

[Enter and evaluate the following:]

	(whitespace-newline-mode 1)
	(global-hl-line-mode 1)
	(setq visual-order-cursor-movement t)

[Then press left-arrow repeatedly.  Cursor will get "stuck" on a line ending.]


Further observations:
- the "-nw" is not necessary - this is just to simplify things.
- `hl-line-mode' alone does not suffice - it has to the be `global-hl-line-mode'.



Second, simpler recipe:

Emacs -Q -nw

[Enter and evaluate the following:]

	(whitespace-newline-mode 1)

Place cursor at end of line, then M-: (move-point-visually -1)  RET.
Nothing happens.







In GNU Emacs 24.3.50.3 (x86_64-apple-darwin13.0.0, NS apple-appkit-1265.00)
 of 2013-12-07 on momo

[git revision 9d4f4d00978ceed46c4c30fe41c258716f9e042e - last change Sat Dec 7 20:46]

Configured using:
 `configure --with-ns'

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

bug#16148: Cursor stuck on line ending w/ visual-order-cursor movement - move-point-visually fails.

[Eli Zaretskii]

> From: David Reitter <david.reitter@gmail.com>
> Date: Sat, 14 Dec 2013 12:53:51 -0500
> 
> With a certain combination of settings, cursor movement to the left fails at the (right) end of lines:
> 
> Emacs -Q -nw
> 
> [Enter and evaluate the following:]
> 
> 	(whitespace-newline-mode 1)
> 	(global-hl-line-mode 1)
> 	(setq visual-order-cursor-movement t)
> 
> [Then press left-arrow repeatedly.  Cursor will get "stuck" on a line ending.]

Fixed.

> - `hl-line-mode' alone does not suffice - it has to the be `global-hl-line-mode'.

That's because move-point-visually uses 2 separate strategies, and the
problem was only in one of them.  You need to work very hard for
move-point-visually to fall back on the second strategy, but the
combination of the above 2 mode, each one of which is a redisplay
optimizations killer, succeeded in doing just that.

> Second, simpler recipe:
> 
> Emacs -Q -nw
> 
> [Enter and evaluate the following:]
> 
> 	(whitespace-newline-mode 1)
> 
> Place cursor at end of line, then M-: (move-point-visually -1)  RET.
> Nothing happens.

This is the same problem (M-: also forces move-point-visually to use
the 2nd strategy), so it is also fixed.

Thanks.