bug#4759: 23.1; Minor Visual Corruption ("Flyspecks") on 23.1/OSX

[Tom Feist]

When scrolling (either via wheel or cursor keys / C-n+p) under certain
conditions the buffer view will become corrupted with tiny 'flyspecks'  
which
appear to be parts of the buffer text which have been incorrectly over- 
drawn.
(That is, they typically share the same colours as the font-locked  
text which
"created" them moves across the screen.)

They remain in position fixed relative to the buffer (They do not move  
with the
text as it scrolls) until either a buffer switch or C-l redraws the  
screen.
They may also be eliminated if a portion of text scrolls over them and  
is
correctly over-drawn.

A sample of the corruption can be seen at
<url:http://metavore.org/faff/emacs-flyspecks.png> along the left-hand  
margin,
approx 7 chars in.

Finally, their occurrence frequency seems to be related to the  
specific face font. They
occur occasionally with the default (Apple-Monaco-13) font, but are  
far more
prevalent with the Anonymous_Pro font (available from
 <url:http://www.ms-studio.com/FontSales/anonymouspro.html>).

As yet I have not found a font which does not cause them, merely  
alters their
relative frequency of occurrence.

Further testing indicates that the problem may be related to anti- 
aliasing of the fonts.
Setting `ns-antialias-text' to nil eliminates the glitches, but at the  
cost of incredibly ugly
fonts, and so isn't really a suitable fix.

Thanks,

Tom Feist.

In GNU Emacs 23.1.1 (i386-apple-darwin9.8.0, NS apple-appkit-949.54)
 of 2009-08-16 on black.local
Windowing system distributor `Apple', version 10.3.949
configured using `configure  '--with-ns''

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: nil
  value of $XMODIFIERS: nil
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  shell-dirtrack-mode: t
  eldoc-mode: t
  cua-mode: t
  global-auto-complete-mode: t
  auto-complete-mode: t
  global-auto-revert-mode: t
  yas/global-mode: t
  yas/minor-mode: t
  diff-auto-refine-mode: t
  show-paren-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-x C-f C-g M-x v e r s i o n <return> C-x C-f . e
m a c s <return> <wheel-down> <double-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<wheel-up> <double-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <wheel-down> M-x
e m a c s - b u g <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading tramp...done
Quit
GNU Emacs 23.1.1 (i386-apple-darwin9.8.0, NS apple-appkit-949.54) of  
2009-08-16 on black.local
OVERVIEW
Starting new Ispell process [en] ...
Restoring clock data
Loading /Users/tomfeist/.emacs.d/org-clock-save.el (source)...done
Loading vc-svn...done
call-interactively: Text is read-only