bug#4858: 23.1.50; Lines truncated, word-wrap=t and truncate-partial-...=nil

With window margins non-nil it sometimes happen that lines are truncated
even though word-wrap is t, truncacte-lines and
truncate-partial-width-windows are both nil.

Setting word-wrap to nil makes the line wraps and when setting it back to t
the lines are truncated again.

I can't easily reproduce it, but I have seen it many times.


In GNU Emacs 23.1.50.1 (i386-mingw-nt5.1.2600)
 of 2009-10-15
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags
-Ic:/g/include -fno-crossjumping'

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: ENU
  value of $XMODIFIERS: nil
  locale-coding-system: cp1252
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-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
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-SPC M-h <up> <down> <down> <down> C-g M-x v i p e
r - m o d e <return> <f10> <menu-bar> <help-menu>
<send-emacs-bug-report>

Recent messages:
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