bug#18793: 24.4; zero width rectangular selection displaces text

[Carlos Pita]

1) Put the point at the beginning of the following sequence of a's.
2) Start a rectangular selection with C-x Space.
3) Move the point one char to the right.
4) Move it one char to the left so that it returns to the left margin.
5) Repeat 3 and 4 a number of times.

aaaaaaaaaaa

Do you see how the sequences of a's moves back and forward? This is not
nice and the example is not that artificial. Having lines separated by
empty lines is very common, so:

1) Put the point at the beginning of the following sequence of a's.
2) Start a rectangular selection with C-x Space.
3) Move the point one char to the right to make the selection width = 1.
4) Move the point down 5 times to extend the selection up to the line of c's.

aaaaaaaaaaa

bbbbbbbbbbb

ccccccccccc

Text looks like jelly, doesn't it? I understand that having a visual
indicator of the empty selection is a good thing but what about the
following alternatives:

a) Keep the thin line near the fringe even when the selection is not
zero width, so no displacement will happen. Or,

b) Use the fringe instead of the buffer.








In GNU Emacs 24.4.1 (i686-pc-linux-gnu, GTK+ Version 3.12.2)
 of 2014-10-22 on carlos
Windowing system distributor `The X.Org Foundation', version 11.0.11502000
Configured using:
 `configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --with-x-toolkit=gtk3 --with-xft
 'CFLAGS=-march=i686 -mtune=generic -O2 -pipe -fstack-protector-strong
 --param=ssp-buffer-size=4' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'

Important settings:
  value of $LC_COLLATE: C
  value of $LC_TIME: es_AR.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Article

Minor modes in effect:
  show-paren-mode: t
  shell-dirtrack-mode: t
  yas-global-mode: t
  yas-minor-mode: t
  ido-ubiquitous-mode: t
  ido-everywhere: t
  winner-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <down-mouse-4> <mouse-4> <double-down-mouse-4> 
<double-mouse-4> <triple-down-mouse-4> <triple-mouse-4> 
<triple-down-mouse-4> <triple-mouse-4> <triple-down-mouse-4> 
<triple-mouse-4> <triple-down-mouse-4> <triple-mouse-4> 
<triple-down-mouse-4> <triple-mouse-4> <triple-down-mouse-4> 
<triple-mouse-4> <down-mouse-5> <mouse-5> <double-down-mouse-5> 
<double-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <down-mouse-5> 
<mouse-5> <double-down-mouse-5> <double-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> C-x k <return> <down> <down> <down> 
<down> <down> <up> <up> C-x SPC <up> <up> <right> <right> 
<right> <right> <right> <right> <up> <up> <up> <up> 
<up> <up> <up> <up> <up> <up> <up> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<up> <up> <up> <up> <up> <up> <up> <up> C-g <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <up> <up> <up> <up> <up> <up> <up> <up> <prior> 
<prior> <up> <up> <up> <up> C-SPC <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <up> <up> 
<up> C-x SPC <down> <down> <down> <down> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <left> <left> <left> <left> <left> <left> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> <right> <up> 
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up> 
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up> 
<down> <down> <up> <right> <right> <right> <left> <left> 
<down> <right> <down> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> C-g <up> M-x r e p o r t - 
e m a c s <tab> <return>

Recent messages:
byte-code: Beginning of buffer
Contacting host: www.google.com.ar:80
byte-code: End of buffer [4 times]
Mark set
Mark set (rectangle mode)
Quit
End of buffer [2 times]
scroll-down-command: Beginning of buffer
Mark set
Rectangle-Mark mode enabled
Quit

Load-path shadows:
~/.emacs.d/lisp/rmail hides /usr/share/emacs/24.4/lisp/mail/rmail

Features:
(shadow emacsbug sendmail rect url-queue timezone shr-color color
url-http url-gw url-auth eww mm-url shr sort smiley gnus-cite mail-extr
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url-privacy url-expand url-methods url-history url-cookie url-domsuf
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gnus-start gnus-spec gnus-int gnus-range message idna rfc822 mml mml-sec
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text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 8 329590 34438)
 (symbols 24 43603 0)
 (miscs 20 317 1004)
 (strings 16 96587 8119)
 (string-bytes 1 3029362)
 (vectors 8 43899)
 (vector-slots 4 1544164 30648)
 (floats 8 797 571)
 (intervals 28 539 279)
 (buffers 512 31)
 (heap 1024 70848 1737))