When a window is selected by a command like `compile-goto-error', and the
buffer of that window have follow-mode enabled, the wrong location is
displayed.

Steps to repeat:

    emacs -Q src/alloc.c
    Make the window wide enough for three columns.
    C-x 3
    C-x 3
    M-x balance-windows RET
    M-x follow-mode RET
    C-x o
    C-x o
    M-x grep RET for *.c RET
    C-x o
    Go to a match of a line number a couple of pages into alloc.c, say line
1001
    RET
    Here, alloc.c is selected, but the wrong line is displayed.

This worked in Emacs 24.2 but is broken in Emacs 24.3 and on the bzr trunk.

The cause of the error seems to be a major rewrite of follow-mode. In the
24.2 version, the function `follow-post-command-hook' picked up the point
to work on, "dest", from the buffer associated with the window. In 24.3, is
simply use `(point)' of the current buffer.

I guess that this is a mistake introduced when the new function
`follow-adjust-window' was broken out from `follow-post-command-hook'.
"dest" is now a parameter of the new function, unfortunately, in the call
"(point)" is passed, which is located outside of the `(with-current-buffer
(window-buffer win) ...)' construct. Hence, it uses the point of the
current buffer rather than of the buffer of the selected window, which it
should.


(defun follow-post-command-hook ()
  "Ensure that the windows in Follow mode are adjacent after each command."
  (unless (input-pending-p)
    (let ((follow-inside-post-command-hook t)
  (win (selected-window)))
      ;; Work in the selected window, not in the current buffer.
      (with-current-buffer (window-buffer win)
(unless (and (symbolp this-command)
     (get this-command 'follow-mode-use-cache))
  (setq follow-windows-start-end-cache nil)))
      (follow-adjust-window win (point)))))      <-----        **** Outside
`with-current-buffer'.

(defun follow-adjust-window (win dest)
  ;; Adjust the window WIN and its followers.
  ...)

Clearly, the parameter `dest' gets its value from (point). However, as this
is outside the `with-current-buffer' construct it get it's value from
current buffer, not the buffer of the selected window (as before).

It should be trivial to fix, e.g. by adding `dest' to the `let', and
setting in the `with-current-construct' of `follow-post-command-hook', and
pass it, rather than (point) -- but I leave it to you to do the actual
implementation.

Sincerely,
    Anders Lindgren

Ps. I'm the original author of Follow mode.

In GNU Emacs 24.3.50.1 (x86_64-apple-darwin13.0.0, NS apple-appkit-1265.00)
 of 2014-01-09 on macpro.lan
Repository revision: 115931
monnier@iro.umontreal.ca-20140109015919-e2odlbm4kphig5ya
Windowing system distributor `Apple', version 10.3.1265
Configured using:
 `configure --with-ns'

Important settings:
  value of $LC_CTYPE: UTF-8
  locale-coding-system: utf-8-unix

Major mode: Help

Minor modes in effect:
  shell-dirtrack-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> F o
l l o w SPC m o d e SPC v b <backspace> <backspace>
b r o k n SPC <backspace> <backspace> e n SPC w h e
n SPC s t a r t e d SPC <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
w i n d o w SPC s e l e c t e d SPC f r o m <backspace>
<backspace> <backspace> <backspace> b u t SPC c u <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
b u r SPC <backspace> <backspace> t SPC c u r r e n
t SPC b u f f e r SPC s <backspace> i s <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> s e l e c t e d SPC <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> w <backspace> w h e n SPC <left>
<left> <left> <left> <left> <left> <left> <left> <left>
<left> <left> <left> <left> <left> <left> <left> <left>
<left> <right> <backspace> . <backspace> - C-e <backspace>
<backspace> <backspace> <backspace> h e n SPC <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> C o m p i l e <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> C-x p C-x p C-x o C-x o C-x o C-x o C-h
k <return> <down> <down> <down> C-x o C-x o C-x o <escape>
x <up> <return>

Recent messages:
follow-post-command-hook
follow-adjust-window
C-x p is undefined [3 times]
Making completion list...
Undo! [5 times]
Quit
C-x p is undefined
Quit
C-x p is undefined
Type "q" to restore previous buffer.

Load-path shadows:
None found.

Features:
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