Bug#389476: xterm: ansi color slows scrolling down
Package: xterm
Version: 210-3
Severity: minor
I've noticed that there is a considerable slowdown in scrolling speed
when lines contain ansi-color codes that change the background (!)
colour.
This slowdown is hardly noticeable on a reasonably fast machine, but
on my trusty old toshiba libretto (only 266 Mhz, but I'll never part
with it) listing a directory with 200 files with ls --color=yes is
unbearably slow.
This must have crept in a few updates ago, I can't remember scrolling
being that slow on the laptop before. It's not fixed in 210-3.1
(tested on the laptop, uses same distribution and software, but
neomagic display hardware) and not in upstream (220) either.
The following loop in a bash tests that behaviour:
bogomips=`grep bogomips /proc/cpuinfo|tail -1|cut -f2 -d:|cut -f1 -d.`; wallclock=`date +%s`;i=0; while [ $i -lt $bogomips ]; do echo -e "\033[47m$i\033[00m"; i=$(($i + 1)); done; echo $((`date +%s` - $wallclock)) seconds
Outputs numbers up to $bogomips with white background. Will take about
10 seconds on my athlon 550 at home and the machines at work (intel
2800 mhz), and about 55 seconds on my laptop. I assume something
causes additional sluggishness on the laptop (maybe the display
driver? There's an old bug at
https://bugs.freedesktop.org/show_bug.cgi?id=1877 which might be
related).
The slowdown only happens when the background colour is changed, so if
you change the first escape sequence in the echo string to e.g.
"\033[31m" (red foreground) the whole loop takes about 1 second.
Also there is no slowdown in rxvt, on any machine.
I think this should probably be forwarded to upstream but I'd like it
to be in the debian BTS nonetheless.
Finally I manage to hit a bug that is actually reproducible! :)
Kind regards
Friedel
-- System Information:
Debian Release: testing/unstable
APT prefers unstable
APT policy: (990, 'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: i386 (i686)
Shell: /bin/sh linked to /bin/bash
Kernel: Linux 2.6.17-2-k7
Locale: LANG=de_DE.utf8, LC_CTYPE=de_DE.utf8 (charmap=UTF-8) (ignored: LC_ALL set to de_DE.utf8)
Versions of packages xterm depends on:
ii libc6 2.3.6.ds1-4 GNU C Library: Shared libraries
ii libfontconfig1 2.3.2-7 generic font configuration library
ii libice6 1:1.0.0-3 X11 Inter-Client Exchange library
ii libncurses5 5.5-2 Shared libraries for terminal hand
ii libsm6 1:1.0.0-4 X11 Session Management library
ii libx11-6 2:1.0.0-8 X11 client-side library
ii libxaw7 1:1.0.2-4 X11 Athena Widget library
ii libxext6 1:1.0.1-2 X11 miscellaneous extension librar
ii libxft2 2.1.8.2-8 FreeType-based font drawing librar
ii libxmu6 1:1.0.1-3 X11 miscellaneous utility library
ii libxt6 1:1.0.0-5 X11 toolkit intrinsics library
ii xbitmaps 1.0.1-2 Base X bitmaps
Versions of packages xterm recommends:
ii xutils 1:7.1.ds-1 X Window System utility programs
-- no debconf information
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