bug#35067: 26.1; Editing particular .html file is slow.

bug#35067: 26.1; Editing particular .html file is slow.

[Scott Haines]

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Dear Emacs maintainers:

Here are the steps to see Emacs editing this .html file very slowly.

1. Copy the file http://gnuplot.sourceforge.net/demo_canvas_5.2/simple.html
to your computer and open it in Emacs. 

2. Press the down arrow key repeatedly.
3. Around row 55 Emacs will become very slow in its response.
This .html file has JavaScript. This may or may not be significant.

Yours truly,
Scott Haines



In GNU Emacs 26.1 (build 1, x86_64-w64-mingw32)
 of 2018-05-30 built on CIRROCUMULUS
Repository revision: 07f8f9bc5a51f5aa94eb099f3e15fbe0c20ea1ea
Windowing system distributor 'Microsoft Corp.', version 10.0.17763
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS THREADS LCMS2

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

Major mode: HTML+

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-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
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc dired dired-loaddefs rfc822
mml mml-sec epa epg mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail mhtml-mode css-mode smie color
eww puny mm-url gnus nnheader gnus-util rmail rmail-loaddefs rfc2047
rfc2045 ietf-drums mail-utils wid-edit mm-util mail-prsvr url-queue url
url-proxy url-privacy url-expand url-methods url-history url-cookie
url-domsuf url-util mailcap shr svg xml browse-url format-spec js advice
json map imenu thingatpt cc-mode cc-fonts cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs sgml-mode dom flyspell
ispell gnugo derived pcase easy-mmode finder-inf package easymenu
epg-config url-handlers url-parse auth-source cl-seq eieio eieio-core
cl-macs eieio-loaddefs password-cache url-vars seq byte-opt gv bytecomp
byte-compile cconv cl-loaddefs cl-lib time-date mule-util 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
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 w32notify w32 lcms2
multi-tty make-network-process emacs)

Memory information:
((conses 16 183849 9126)
 (symbols 56 28776 1)
 (miscs 48 42 100)
 (strings 32 55494 1453)
 (string-bytes 1 1574531)
 (vectors 16 23680)
 (vector-slots 8 599193 7740)
 (floats 8 241 348)
 (intervals 56 1193 1558)
 (buffers 992 12))

Sent from Mail for Windows 10


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bug#35067: 26.1; Editing particular .html file is slow.

[Eli Zaretskii]

On April 1, 2019 8:59:07 AM GMT+03:00, Scott Haines <scotthaines.mn@comcast.net> wrote:
> 
> 
> Dear Emacs maintainers:
> 
> Here are the steps to see Emacs editing this .html file very slowly.
> 
> 1. Copy the file
> http://gnuplot.sourceforge.net/demo_canvas_5.2/simple.html
> to your computer and open it in Emacs. 
> 
> 2. Press the down arrow key repeatedly.
> 3. Around row 55 Emacs will become very slow in its response.
> This .html file has JavaScript. This may or may not be significant.


That file has a 100K line in the area where you see slowdown.  Emacs has known problems with displaying very long lines.

On my system, the slowdown is bearable, at least in "emacs -Q", and turning on truncate-lines makes display fast again.  If you see this in a customized session, perhaps some of the customizations add more slowdown.