Flickering of mode line buttons

[Marshall, Simon]

src/emacs -Q
C-x 2           ; split windows makes flickering more obvious

In the selected window, move the mouse across the "*scratch*" or "Lisp
Interaction" mode-line buttons.  I see the other buttons, particularly the
buttons on the left (coding, read-only, modified) flickering as they are
repeatedly redrawn.  (It's possible that the whole mode-line is being
repeatedly redrawn - it's more obvious with the buttons.)  I also see
redrawing continue intermittently for a few seconds after I stop moving the
mouse (though still within a button).

In GNU Emacs 22.0.50.1 (sparc-sun-solaris2.8, X toolkit)
 of 2006-09-11 on perth
X server distributor `Hummingbird Ltd.', version 11.0.100015
configured using `configure 'CFLAGS=-g''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: en_GB.ISO8859-1
  value of $LC_CTYPE: en_GB.ISO8859-1
  value of $LC_MESSAGES: C
  value of $LC_MONETARY: en_GB.ISO8859-1
  value of $LC_NUMERIC: en_GB.ISO8859-1
  value of $LC_TIME: en_GB.ISO8859-1
  value of $LANG: en_GB.ISO8859-1
  locale-coding-system: iso-8859-1
  default-enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-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
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  line-number-mode: t