bug#21662: 25.0.50; visible-bell causes display artifacts on OS X 10.11

[Steve Purcell]

I'm using snapshot builds from emacsformacosx.com on my Macbook, and I
have `visible-bell' set to t. Since upgrading OS X from 10.10 to 10.11 I
see display artifacts: specifically, there appears to be no redraw after
the visible bell square flashes in the centre of the frame, so the frame
contents are left obscured or blurred.

I had initially noticed this with an older snapshot build, and have
verified that it still occurs using the latest snapshot (dated Oct
10).

Happy to provide further info upon request.



In GNU Emacs 25.0.50.1 (x86_64-apple-darwin13.4.0, NS appkit-1265.21 Version 
10.9.5 (Build 13F1112))
 of 2015-10-10
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp''

Configured features:
ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

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

Major mode: Emacs-Lisp

Minor modes in effect:
  shell-dirtrack-mode: t
  global-flycheck-mode: t
  flycheck-mode: t
  elisp-slime-nav-mode: t
  redshank-mode: t
  aggressive-indent-mode: t
  rainbow-delimiters-mode: t
  highlight-quoted-mode: t
  highlight-symbol-nav-mode: t
  highlight-symbol-mode: t
  diff-hl-mode: t
  diff-auto-refine-mode: t
  bug-reference-prog-mode: t
  paredit-mode: t
  goto-address-prog-mode: t
  auto-insert-mode: t
  auto-compile-on-load-mode: t
  auto-compile-on-save-mode: t
  auto-compile-mode: t
  ipretty-mode: t
  global-rinari-mode: t
  guide-key-mode: t
  hes-mode: t
  global-page-break-lines-mode: t
  page-break-lines-mode: t
  delete-selection-mode: t
  cua-mode: t
  show-paren-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  global-whitespace-cleanup-mode: t
  whitespace-cleanup-mode: t
  global-auto-revert-mode: t
  electric-pair-mode: t
  savehist-mode: t
  desktop-save-mode: t
  winner-mode: t
  global-auto-complete-mode: t
  auto-complete-mode: t
  ido-ubiquitous-mode: t
  ido-everywhere: t
  recentf-mode: t
  global-anzu-mode: t
  anzu-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  global-prettify-symbols-mode: t
  prettify-symbols-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Desktop: 26.79ms to restore nil
Desktop: 24.35ms to restore nil
Wrote /Users/steve/.emacs.d/.emacs.desktop.lock
Desktop: 1 frame, 72 buffers restored.
Desktop restored in 12698.73ms
For information about GNU Emacs and the GNU system, type C-h C-a.
Evaluating...
t
Quit [3 times]
Press key for agenda command:

Load-path shadows:
/Users/steve/.emacs.d/elpa/helm-20151009.1117/helm-multi-match hides 
/Users/steve/.emacs.d/elpa/helm-core-20151009.905/helm-multi-match
/Users/steve/.emacs.d/elpa/emms-20150810.832/tq hides 
/Applications/Emacs.app/Contents/Resources/lisp/emacs-lisp/tq

Features:
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Memory information:
((conses 16 1076507 477227)
 (symbols 48 57378 0)
 (miscs 40 7194 9146)
 (strings 32 159666 250836)
 (string-bytes 1 4581130)
 (vectors 16 113288)
 (vector-slots 8 1498997 875754)
 (floats 8 1030 1234)
 (intervals 56 30825 2420)
 (buffers 976 93))