bug#37784: Buffer messed up when scrolling undecorated frame

bug#37784: Buffer messed up when scrolling undecorated frame

[Carlos Pita]

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When I set:

(set-frame-parameter nil 'undecorated t)

and then change to another window and back to emacs, then scroll
around the window, I often end up with a very messed up buffer and
have to run redraw-display in order to sanitize its contents. See
attached screenshot.

I've tested this in an environment featuring:

* Gnome 3.32
* Ubuntu 19.04
* Emacs built from emacs-26 branch (of course, run with -Q)

After restoring decorations the problem stop happening.

Any idea about what could be causing this?

Best regards
--
Carlos

---

In GNU Emacs 26.3.50 (build 11, x86_64-pc-linux-gnu, GTK+ Version
3.24.8, cairo version 1.16.0)
 of 2019-10-16 built on carlos
Repository revision: 116a7369bcb97341be7d6ffe3f832bf52159a99a
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Ubuntu 19.04

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...

Configured using:
 'configure --prefix=/home/carlos/Local/stow/emacs-26 --with-cairo
 'CFLAGS=-O3 -g0''

Configured features:
XPM JPEG TIFF GIF PNG CAIRO SOUND DBUS GSETTINGS GLIB NOTIFY LIBSELINUX
GNUTLS FREETYPE XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM THREADS

Important settings:
  value of $LC_MONETARY: es_AR.UTF-8
  value of $LC_NUMERIC: es_AR.UTF-8
  value of $LC_TIME: es_AR.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  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 message rmc puny seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils elec-pair time-date
mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page menu-bar
rfn-eshadow isearch timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core term/tty-colors frame cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads dbusbind
inotify dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 94873 8334)
 (symbols 48 20247 1)
 (miscs 40 44 118)
 (strings 32 28311 1604)
 (string-bytes 1 753138)
 (vectors 16 13910)
 (vector-slots 8 501264 11006)
 (floats 8 49 68)
 (intervals 56 231 0)
 (buffers 992 12))

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bug#37784: Buffer messed up when scrolling undecorated frame

[Carlos Pita]

Very easily reproducible in emacs-26.2 tag also, but not in master
branch. Do you know what commit could have fixed this? I would like to
backport the change to emacs-26.

bug#37784: Buffer messed up when scrolling undecorated frame

[Lars Ingebrigtsen]

Carlos Pita <carlosjosepita@gmail.com> writes:

> Very easily reproducible in emacs-26.2 tag also, but not in master
> branch. Do you know what commit could have fixed this? I would like to
> backport the change to emacs-26.

There will probably be no further emacs-26 releases, so that seems
unnecessary.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#37784: Buffer messed up when scrolling undecorated frame

[Carlos Pita]

> There will probably be no further emacs-26 releases, so that seems
> unnecessary.

I know, it's just for personal usage, just if anybody aware of this
issue could spare me the pain of bisecting it. Anyway, we can close
this. Thx!

bug#37784: Buffer messed up when scrolling undecorated frame

[Eli Zaretskii]

> From: Carlos Pita <carlosjosepita@gmail.com>
> Date: Wed, 16 Oct 2019 21:52:24 -0300
> 
> When I set:
> 
> (set-frame-parameter nil 'undecorated t)
> 
> and then change to another window and back to emacs, then scroll
> around the window, I often end up with a very messed up buffer and
> have to run redraw-display in order to sanitize its contents. See
> attached screenshot.

What happens if you trigger redisplay after that setting, but before
switching off from the Emacs frame?

bug#37784: Buffer messed up when scrolling undecorated frame

[Eli Zaretskii]

> From: Carlos Pita <carlosjosepita@gmail.com>
> Date: Wed, 16 Oct 2019 22:50:47 -0300
> 
> Very easily reproducible in emacs-26.2 tag also, but not in master
> branch. Do you know what commit could have fixed this? I would like to
> backport the change to emacs-26.

Please don't do any development of new features on Emacs 26, it will
save you from bumping into bugs that are long solved.

bug#37784: Buffer messed up when scrolling undecorated frame

[martin rudalics]

 > I know, it's just for personal usage, just if anybody aware of this
 > issue could spare me the pain of bisecting it.

If and when you get around bisecting this, please tell us the results.
Maybe there was or is some further breakage in this area.

I would try building Emasc 26 without Cairo first, there are some
essential fixes for Cairo in Emacs 27 and I'm not sure whether they
have been all ported back to Emacs 26.3.

martin