I have fixed this in the trunk, but I'm not satisfied with the solution, but it will have to do for now.
The problem has to do with LCD-smoothing. As you can see in the attached picture
one pixel of the A in the lower right corner extends in to the box for T. As Emacs does not know about these pixels, when we write a Y over the A, the pixel remains.
You can see the same effect when Y is replaced with for example A. The top right part of the Y has an extra pixel in the next character box, that remains.
The current solution is to turn off LCD-smoothing. A better solution would be to draw the whole line every time. Or somehow keep track of adjacent characters that needs to be redrawn. But that may involve the display engine and is a bigger task.
Jan D.
16 maj 2012 kl. 00:02 skrev Frank Marcoline <fvmarcoline@gmail.com>:
Bug: Scrolling can leave behind traces of old text.
The traces appear to be cyan outlines of the right hand
side of characters which previously occupied the same location.
For example, a "Y" will leave behind a small cyan dot from its upper
right, an "A" will leave behind a small cyan dot from its lower right.
Steps to reproduce:
1) /Applications/Emacs.app/Contents/MacOS/Emacs -Q
2) C-x C-f helix.pqr [Ret]
3) Rapidly scroll up and down with two-finger drag gesture
I have attached the file helix.pqr, for which the effect is
very pronounced, and a screenshot faithfully reproducing
the effect. Note the small cyan marks on the left of
many numbers and letters.
This version of emacs came from http://emacsformacosx.com/
In GNU Emacs 23.4.1 (x86_64-apple-darwin, NS apple-appkit-1038.36)
of 2012-01-29 on bob.porkrind.org
Windowing system distributor `Apple', version 10.3.1138
configured using `configure '--host=x86_64-apple-darwin'
'--build=i686-apple-darwin' '--with-ns'
'build_alias=i686-apple-darwin' 'host_alias=x86_64-apple-darwin'
'CC=gcc -mmacosx-version-min=10.5''
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
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
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
auto-encryption-mode: t
auto-compression-mode: t
line-number-mode: t
transient-mark-mode: t
Recent input:
<wheel-up> <double-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <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> <triple-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> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <wheel-down> <double-wheel-down>
<triple-wheel-down> <wheel-up> <double-wheel-up> <triple-wheel-up>
<wheel-up> <double-wheel-up> <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> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <wheel-down>
<double-wheel-down> <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> <triple-wheel-down> <triple-wheel-down>
<wheel-up> <double-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <wheel-up> <double-wheel-up> <wheel-down>
<wheel-down> <double-wheel-down> <wheel-up> <wheel-down>
<wheel-down> <wheel-up> <double-wheel-up> <wheel-up>
<wheel-up> <double-wheel-up> <triple-wheel-up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <down> <down> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <down> C-x b <return>
<wheel-up> <double-wheel-up> <triple-wheel-up> <triple-wheel-up>
<wheel-down> <double-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> <wheel-down> <double-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <wheel-up> <double-wheel-up> <wheel-down>
<double-wheel-down> <triple-wheel-down> <wheel-down>
<double-wheel-down> <triple-wheel-down> <wheel-up>
<double-wheel-up> <triple-wheel-up> <triple-wheel-up>
<wheel-down> <double-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> <wheel-down> <double-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>
<wheel-down> <double-wheel-down> <triple-wheel-down>
<wheel-up> <double-wheel-up> <triple-wheel-up> <wheel-down>
<double-wheel-down> <wheel-down> <double-wheel-down>
M-x b u g <tab> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> r e p <tab> o r <tab> <return>
Recent messages:
Saving file /Users/fvm/.emacs...
Wrote /Users/fvm/.emacs
byte-code: Beginning of buffer [8 times]
byte-code: End of buffer [13 times]
byte-code: Beginning of buffer [13 times]
byte-code: End of buffer [26 times]
byte-code: Beginning of buffer [14 times]
byte-code: End of buffer [2 times]
Making completion list...
byte-code: End of buffer [4 times]
Load-path shadows:
None found.
Features:
(shadow sort mail-extr message ecomplete rfc822 mml mml-sec
password-cache mm-decode mm-bodies mm-encode mailcap mail-parse rfc2231
rfc2047 rfc2045 qp ietf-drums mailabbrev nnheader gnus-util netrc
time-date mm-util mail-prsvr gmm-utils wid-edit mailheader canlock sha1
hex-util hashcash mail-utils emacsbug help-mode view vc-hg cc-mode
cc-fonts cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
regexp-opt tooltip ediff-hook vc-hooks lisp-float-type mwheel ns-win
easymenu tool-bar dnd fontset image fringe lisp-mode register page
menu-bar rfn-eshadow timer select scroll-bar mldrag mouse jit-lock
font-lock syntax facemenu font-core frame cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew
greek romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev loaddefs button
minibuffer faces cus-face files text-properties overlay md5 base64
format env code-pages mule custom widget hashtable-print-readable
backquote make-network-process ns multi-tty emacs)
<helix.pqr><Screen Shot 2012-05-15 at 2.54.44 PM.png>