bug#16470: 24.3.50; term mode and newlines with some window configurations

[Constantine Vetoshev <vetoshev@gmail.com>]

Working with a build from today's Git mirror, revision 41c2162. Running Emacs with -Q.

Something is wrong with term.el's handling of newlines in some window configurations.

The following steps reproduce the bug consistently on my machine:

0. Make sure you have no .zshrc file in your home directory.
1. Start Emacs (with -Q).
2. Stretch the frame so it has enough room for three reasonably large vertical splits.
3. Make 3 equally-sized vertical windows (C-x 3, C-x 3, C-x 3, C-x =).
4. Put your cursor in the right-most window.
5. Run M-x term, then select /bin/zsh as your shell. You should immediately see the inverted '%' which indicates newline oddness with zsh. If you run any command, e.g., ls, you will see '%' at the end of all output.
6. Try running 'unsetopt prompt_sp' in the zsh instance. You'll see the '%' go away, but this is undesirable, because it means that, e.g., 'echo -n hi' does not work properly.

Here is where things get even more strange.

7. exit from the zsh shell and kill the *terminal* buffer.
8. C-x 1 so you have just one empty *scratch* window.
9. M-x term, select /bin/zsh again.
10. No bad '%' behavior occurs now.

To summarize: when you make three vertical windows, term.el's handling of newlines breaks. The behavior seems tied to window splits. I have tried this with term-suppress-hard-newline set to t and nil, and it does not seem to make a difference.


In GNU Emacs 24.3.50.1 (x86_64-apple-darwin13.0.0, NS apple-appkit-1265.00)
 of 2014-01-16 on athena.local
Repository revision: 
Windowing system distributor `Apple', version 10.3.1265
Configured using:
 `configure --with-ns'

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

Major mode: Lisp Interaction

Minor modes in effect:
  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
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<help-echo> C-x <help-echo> 3 <help-echo> <down-mouse-1> 
<mouse-1> M-x t e r m <return> <return> l s <return> 
e x t i <backspace> <backspace> i t <return> <help-echo> 
C-x k <return> C-x 3 C-x + <help-echo> <down-mouse-1> 
<mouse-1> s-x M-x t e r m <return> <return> l s <return> 
e x i t <return> C-d C-x k <return> <help-echo> C-x 
C-g M-x t e r m <return> <return> e x i t <return> 
<help-echo> <help-echo> C-x 0 s-x M-x r e p o r t - 
<tab> <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
call-interactively: End of buffer
C-x C-g is undefined

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util
help-fns mail-prsvr mail-utils term disp-table easymenu ehelp ring
time-date tooltip electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel ns-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list newcomment lisp-mode prog-mode register page menu-bar
rfn-eshadow timer select scroll-bar mouse jit-lock font-lock syntax
facemenu font-core frame cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese hebrew greek romanian slovak
czech european ethiopic indian cyrillic chinese case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer nadvice loaddefs button
faces cus-face macroexp files text-properties overlay sha1 md5 base64
format env code-pages mule custom widget hashtable-print-readable
backquote make-network-process cocoa ns multi-tty emacs)