mouse-drag-mode-line-1 bug or feature?

[Stephen Berman]

1. emacs -Q (or -q)
2. C-x 2
3. Put the mouse pointer over the upper mode line, click mouse-1 and
drag the mouse up or down, thereby raising or lowering the upper mode
line, then release mouse-1. 
4. Put the mouse pointer over the lower mode line, click mouse-1 and
drag the mouse down: nothing happens.  This is as I expect.
5. Put the mouse pointer over the lower mode line, click mouse-1 and
drag the mouse up: the *upper* mode line moves down or up until the
vertically centered position (after step 2) is restored.  This
surprised me. 

I never noticed the behavior in (5) until just now, but it's been
there for some time (it's there in an Emacs 22 binary I still have
from last November, earlier ones I don't have any more), but it's not
in Emacs 21.3 (i.e., there dragging the lower mode line of an
unequally vertically split window does not move the upper mode line).
If it's a feature it is undocumented (at least I couldn't find any
mention of it; if I've overlooked its documentation, sorry for the
noise). 



In GNU Emacs 22.0.50.10 (i686-pc-linux-gnu, GTK+ Version 2.8.7)
 of 2006-02-12 on escher
X server distributor `The X.Org Foundation', version 11.0.60802000
configured using `configure '--with-x-toolkit=gtk''

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: en_US.UTF-8
  locale-coding-system: utf-8
  default-enable-multibyte-characters: t

Major mode: Group

Minor modes in effect:
  gnus-topic-mode: t
  gnus-undo-mode: t
  tabbar-mwheel-mode: t
  tabbar-mode: t
  recentf-mode: t
  show-paren-mode: t
  display-time-mode: t
  tooltip-mode: t
  auto-compression-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  column-number-mode: t
  line-number-mode: t

Recent input:
u C-w . <backspace> - d C-w - m o d C-s C-w C-w C-s 
C-g C-f C-a <down-mouse-1> <mouse-movement> <mouse-movement> 
<drag-mouse-1> <right> C-x C-f <up> . 5 <tab> <return> 
C-s C-s C-s <up> <S-up> C-c j h e <tab> <return> <help-echo> 
<down-mouse-1> <mouse-2> <help-echo> <f1> <down-mouse-5> 
<mouse-5> <down-mouse-5> <mouse-5> <down-mouse-4> <mouse-4> 
<double-down-mouse-4> <double-mouse-4> <triple-down-mouse-4> 
<triple-mouse-4> <down-mouse-4> <mouse-4> <double-down-mouse-4> 
<double-mouse-4> <triple-down-mouse-4> <triple-mouse-4> 
<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> <down-mouse-5> <mouse-5> <double-down-mouse-5> 
<double-mouse-5> <S-left> <S-left> <S-up> <S-right> 
M-x e m a <tab> r e <tab> p <tab> <backspace> <backspace> 
<backspace> <M-backspace> r e p o <tab> r <tab> <r
eturn>

Recent messages:
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