bug#39188: closed (28.0.50; w32 cursor redisplay problem)

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Your message dated Tue, 21 Jan 2020 18:32:54 +0200
with message-id <address@hidden>
and subject line Re: bug#39188: 28.0.50; w32 cursor redisplay problem
has caused the debbugs.gnu.org bug report #39188,
regarding 28.0.50; w32 cursor redisplay problem
to be marked as done.

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39188: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=39188
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--- Begin Message --- Subject: 28.0.50; w32 cursor redisplay problem Date: Sun, 19 Jan 2020 10:17:01 +0100

With the current master (and for a couple of months), I observe this redisplay problem where moving the cursor up or down, when the buffer is scrolled, the cursor may leave some ghost trace. This is with w32-use-visible-system-caret set to t. It seems the problem does not happen if this variable is set to nil.

Picture with several traces of the cursor :

Best regards,

Fabrice

In GNU Emacs 28.0.50 (build 1, x86_64-w64-mingw32)
 of 2020-01-18 built on MARVIN
Repository revision: 17db2bd9c17c84c647d8093a7f03f1b0a55ddcc4
Repository branch: windows
Windowing system distributor 'Microsoft Corp.', version 10.0.19041
System Description: Microsoft Windows 10 Education (v10.0.2004.19041.21)

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list... [2 times]
previous-line: Beginning of buffer [21 times]
Unable to read file "c:/Home/Org/templates/level-0.org" [2 times]
previous-line: Beginning of buffer [18 times]
Making completion list...
previous-line: Beginning of buffer [30 times]
Making completion list...
user-error: End of history; no default available

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS NOTIFY W32NOTIFY ACL GNUTLS
LIBXML2 HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS MODULES THREADS JSON PDUMPER
LCMS2 GMP

Important settings:
  value of $LANG: fr_FR
  locale-coding-system: cp1252

Major mode: Org

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-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-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug sendmail tango-dark-theme ffap thingatpt
org-element avl-tree generator ol-eww ol-rmail ol-mhe ol-irc ol-info
ol-gnus nnir gnus-sum url url-proxy url-privacy url-expand url-methods
url-history mailcap shr url-cookie url-domsuf url-util url-parse
auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs json map
url-vars svg xml dom browse-url gnus-group gnus-undo gnus-start
gnus-cloud nnimap nnmail mail-source utf7 netrc nnoo parse-time iso8601
gnus-spec gnus-int gnus-range message rmc puny rfc822 mml mml-sec
password-cache epa derived epg epg-config mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader gnus-win gnus
nnheader gnus-util rmail rmail-loaddefs rfc2047 rfc2045 ietf-drums
text-property-search seq byte-opt gv bytecomp byte-compile cconv
mail-utils mm-util mail-prsvr wid-edit ol-docview doc-view jka-compr
image-mode exif dired dired-loaddefs ol-bibtex bibtex ol-bbdb ol-w3m org
ob ob-tangle ob-ref ob-lob ob-table ob-exp org-macro org-footnote
org-src ob-comint org-pcomplete pcomplete comint ansi-color ring
org-list org-faces org-entities time-date subr-x org-version
ob-emacs-lisp ob-core ob-eval org-table ol org-keys org-compat advice
org-macs org-loaddefs format-spec find-func cal-menu calendar
cal-loaddefs vc-git diff-mode easymenu cl-loaddefs cl-lib bug-reference
noutline outline easy-mmode tooltip eldoc electric uniquify ediff-hook
vc-hooks lisp-float-type mwheel dos-w32 ls-lisp disp-table term/w32-win
w32-win w32-vars term/common-win tool-bar dnd fontset image regexp-opt
fringe tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
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base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads w32notify dbusbind w32 lcms2 multi-tty
make-network-process emacs)

Memory information:
((conses 16 167083 14304)
 (symbols 48 18300 1)
 (strings 32 60912 2917)
 (string-bytes 1 2024991)
 (vectors 16 29488)
 (vector-slots 8 331793 13298)
 (floats 8 191 294)
 (intervals 56 1214 0)
 (buffers 1000 14))

--- End Message ---

> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#39188: 28.0.50; w32 cursor redisplay problem
>
>
>
>
> Date: 
>
> Tue, 21 Jan 2020 18:32:54 +0200
>
>
>
>
> > From: Fabrice Popineau <address@hidden>
> > Date: Mon, 20 Jan 2020 19:41:48 +0100
> > Cc: address@hidden
> > 
> > Maybe it is not the most important bug (except if Windows start to tell
> > emacs that there are screen readers everywhere)
>
> I found the problem.  As part of redisplay, we sometimes scroll
> rectangular portions of the window, as pixels, up and down.  When we
> do so, we first turn off the cursor, but when the system caret is used
> instead of the cursor, we hide and unhide the caret in a separate UI
> thread.  So there's a race between the main thread which scrolls the
> pixels and the UI thread that draws the caret, and that race causes
> the pixels of the caret to sometimes be copied with the rectangular
> area that is scrolled.
>
> The solution is to disable the scrolling in w32_scroll_run when the
> system caret is in use.  This slows down redisplay to some extent
> (because w32_scroll_run is a redisplay optimization), but I don't see
> any easy way around that.
>
> Should be fixed now on the emacs-27 branch.
>
>
> --- End Message ---