bug#3347: 23.0.93; unnecessary display updates with mouse-drag-region

[YAMAMOTO Mitsuharu]

Mouse dragging over a text in the default face causes unnecessary
updates in other windows displaying the same buffer.

Steps to reproduce:

  1. Invoke "Quartz Debug.app" on Mac OS X and check the "Flash screen
     updates" button.
  2. $ emacs -Q -D
  3. C-x 2
  4. Drag the mouse over the *scratch* buffer text in the first
     window.

Result:

  The text not only in the first window but also the other one is
  flashed whereas the latter doesn't need updates.  The flashed area
  corresponds to the extended/shrunken part of the region in the first
  window.

The updates in the second window do not happen if the text is in
non-default face (e.g., start with "emacs -Q" instead of "emacs -Q
-D").

I can't observe this phenomenon on Emacs 22.3.

                                     YAMAMOTO Mitsuharu
                                mituharu@math.s.chiba-u.ac.jp

In GNU Emacs 23.0.93.1 (powerpc-apple-darwin9.6.0, X toolkit)
 of 2009-05-22 on yamamoto-mitsuharu-no-power-mac-g5.local
Windowing system distributor `The X.Org Foundation', version 11.0.10402000
configured using `configure  '--without-jpeg' '--without-gif' '--without-tiff''

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: ja_JP.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t