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bug#39733: 26.3; Unclear direct color mode documentation can cause loadi
From: |
Daniel Long Sockwell |
Subject: |
bug#39733: 26.3; Unclear direct color mode documentation can cause loading delays |
Date: |
Fri, 21 Feb 2020 21:36:05 -0500 |
User-agent: |
mu4e 1.1.0; emacs 26.3 |
The Emacs manual describes the process for enabling direct color mode
for terminal Emacs with the following:
> Emacs can be invoked with a custom definition as shown below
>> $ cat terminfo-24bit.src
>>
>> # Use colon separators.
>> xterm-24bit|xterm with 24-bit direct color mode,
>> use=xterm-256color,
>> setb24=\E[48:2:%p1%{65536}%/%d:%p1%{256}%/%{255}%&%d:%p1%{255}%&%dm,
>> setf24=\E[38:2:%p1%{65536}%/%d:%p1%{256}%/%{255}%&%d:%p1%{255}%&%dm,
>> # Use semicolon separators.
>> xterm-24bits|xterm with 24-bit direct color mode,
>> use=xterm-256color,
>> setb24=\E[48;2;%p1%{65536}%/%d;%p1%{256}%/%{255}%&%d;%p1%{255}%&%dm,
>> setf24=\E[38;2;%p1%{65536}%/%d;%p1%{256}%/%{255}%&%d;%p1%{255}%&%dm,
>>
>> $ tic -x -o ~/.terminfo terminfo-24bit.src
>>
>> $ TERM=xterm-24bit emacs -nw
Source: Emacs FAQ, 5.3
I followed these directions literally, and enabled direct color support
in Emacs, apparently without issue. However, what I did not realize was
that I ought *not* to have followed the example literally – instead, I
should have replaced "xterm" with my actual $TERM value. (In
retrospect, that is fairly obvious, but it wasn't at the time, in part
because I've come across other areas where setting a $TERM value of
xterm was a valid workaround. And, as I said, following the directions
literally appeared to work as shown by the output of `M-x
list-colors-display`.)
Months later, I realized that I was experiencing a very odd bug: my
Emacs instance was taking well over 2 seconds to start in a terminal,
even when invoked with `emacs -Q -nw`. Even more oddly, I determined
`M-x emacs-init-time` showed a very low time – whatever was causing the
slowdown was outside of the normal init process. After fairly extensive
testing, I discovered that the slowdown was caused by a pselect
timeout. This one, according to strace:
> pselect6(5, [4], [], NULL, {tv_sec=1, tv_nsec=998526670}, {NULL, 8}) =
> 0 (Timeout) <2.000940>
After even more testing, I determined that the issue was caused by the
terminfo/$TERM settings: apparently, if the user has a $TERM value that
does not match their terminal, Emacs will have a 2-second delay before
launching, waiting for whatever that pselect call is looking for.
Once I finally figured the above out, I decided to file this bug in the
hope that the documentation can be updated and other can avoid spending
as long with this issue as I did. Specifically, I believe that Section
5.3 should be updated to indicate that users should modify the custom
definition provided to use the appropriate $TERM value for their own
terminal.
Beyond that, the fact that an incorrect $TERM setting results in a
2-second delay in launching Emacs may, itself, be an Emacs bug – after
all, the incorrect $TERM/terminfo settings *worked* to display correct
colors in Emacs. It may be that there is a way to avoid this delay, or
at least to signal the error to the user via *Messages*. But I don't
know enough about Emacs' internals to be sure of that.
Either way, it was certainly an interesting process to debug!
Best regards,
Daniel
In GNU Emacs 26.3 (build 1, x86_64-pc-linux-gnu)
of 2019-09-18 built on svetlemodry
System Description: Antergos Linux
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...
Configured using:
'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
--localstatedir=/var --without-x --without-sound --with-modules
'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fno-plt'
CPPFLAGS=-D_FORTIFY_SOURCE=2
LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'
Configured features:
DBUS NOTIFY ACL GNUTLS LIBXML2 ZLIB MODULES THREADS LIBSYSTEMD
Important settings:
value of $LC_COLLATE: en_US.UTF-8
value of $LANG: en_US.UTF-8
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
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
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 tool-bar rmail-loaddefs mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
regexp-opt rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
term/xterm xterm time-date elec-pair mule-util tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type tabulated-list replace
newcomment text-mode elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow isearch timer select 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 multi-tty make-network-process emacs)
Memory information:
((conses 16 97828 8897)
(symbols 48 19448 1)
(miscs 40 40 96)
(strings 32 27649 1398)
(string-bytes 1 739458)
(vectors 16 11875)
(vector-slots 8 449294 5376)
(floats 8 49 66)
(intervals 56 208 0)
(buffers 992 12))
- bug#39733: 26.3; Unclear direct color mode documentation can cause loading delays,
Daniel Long Sockwell <=