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emacs/admin/notes/multi-tty
Eli Zaretskii 19dcb237b5 ; Add 2022 to copyright years.
2022-01-01 02:45:51 -05:00

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-*- coding: utf-8; mode: text; -*-
Copyright (C) 2007-2022 Free Software Foundation, Inc.
See the end of the file for license conditions.
From README.multi-tty in the multi-tty branch.
Some of this information may be out of date.
THANKS
------
The following is a (sadly incomplete) list of people who have
contributed to the project by testing, submitting patches, bug
reports, and suggestions. Thanks!
Bernard Adrian <bernadrian@free.fr>
ARISAWA Akihiro <ari@mbf.ocn.ne.jp>
Vincent Bernat <bernat@luffy.cx>
Han Boetes <han@mijncomputer.nl>
Francisco Borges <borges@let.rug.nl>
Damien Cassou <damien.cassou@laposte.net>
Robert J. Chassell <bob@rattlesnake.com>
Romain Francoise <romain@orebokech.com>
Ami Fischman <ami@fischman.org>
Noah Friedman <friedman@splode.com>
Friedrich Delgado Friedrichs <friedel@nomaden.org>
Samium Gromoff <_deepfire@mail.ru>
Mikhail Gusarov <dottedmag@dottedmag.net>
Eric Hanchrow <offby1@blarg.net>
IRIE Tetsuya <irie@t.email.ne.jp>
Yoshiaki Kasahara <kasahara@nc.kyushu-u.ac.jp>
Bas Kok <nekkobassu@yahoo.com>
Jurej Kubelka <Juraj.Kubelka@email.cz>
David Lichteblau <david@lichteblau.com>
Richard Lewis <rtf@jabble.com>
mace <mace@kirjakaapeli.lib.hel.fi>
Suresh Madhu <madhu@cs.unm.edu>
Xavier Mallard <zedek@gnu-rox.org>
Istvan Marko <mi-mtty@kismala.com>
Ted Morse <morse@ciholas.com>
Gergely Nagy <algernon@debian.org>
Dan Nicolaescu <dann@ics.uci.edu>
Kalle Olavi Niemitalo <kon@iki.fi>
Mark Plaksin <happy@mcplaksin.org>
Frank Ruell <stoerte@dreamwarrior.net>
Tom Schutzer-Weissmann <trmsw@yahoo.co.uk>
Joakim Verona <joakim@verona.se>
Dan Waber <dwaber@logolalia.com>
and many others.
Richard Stallman was kind enough to review an earlier version of my
patches.
STATUS
------
It still needs to be ported to Windows/Mac/DOS. Both multiple
tty device support and simultaneous X and tty frame support works
fine. Emacsclient has been extended to support opening new tty and X
frames. It has been changed to open new Emacs frames by default.
Tested on GNU/Linux, Solaris 8, FreeBSD and OpenBSD.
Known problems:
* GTK support. If you compile your Emacs with the GTK
toolkit, some functionality of multi-tty may be lost. In
particular, you may get crashes while working on multiple X
displays at once. Previous releases of GTK had limitations
and bugs that prevented full-blown multi-display support in
Emacs. (GTK crashed when Emacs tries to disconnect from an
X server.) Things are much improved in the current GTK
version, but if you do experience crashes in libgtk, try
compiling Emacs with the Lucid toolkit instead.
* The single-kboard mode.
If your multi-tty Emacs session seems to be frozen, you
probably have a recursive editing session or a pending
minibuffer prompt (which is a kind of recursive editing) on
another display. To unfreeze your session, switch to that
display and complete the recursive edit, for example by
pressing C-] ('abort-recursive-edit').
I am sorry to say that currently there is no way to break
out of this "single-kboard mode" from a frozen display. If
you are unable to switch to the display that locks the
others (for example because it is on a remote computer),
then you can use emacsclient to break out of all recursive
editing sessions:
emacsclient -e '(top-level)'
Note that this (perhaps) unintuitive behavior is by design.
Single-kboard mode is required because of an intrinsic Emacs
limitation that is very hard to eliminate. (This limitation
is related to the single-threaded nature of Emacs.)
I plan to implement better user notification and support for
breaking out of single-kboard mode from locked displays.
TESTING
-------
To test the multi-tty feature, start up the Emacs server with the
following commands:
emacs
M-x server-start
and then (from a shell prompt on another terminal) start emacsclient
with
emacsclient -t /optional/file/names... (for a tty frame)
emacsclient /optional/file/names... (for an X frame)
(Make sure both emacs and emacsclient are multi-tty versions.)
You'll hopefully have two fully working, independent frames on
separate terminals. The new frame is closed automatically when you
finish editing the specified files (C-x #), but delete-frame (C-x 5 0)
also works. Of course, you can create frames on more than two tty
devices.
Creating new frames on the same tty with C-x 5 2 (make-frame-command)
works, and behaves the same way as in previous Emacs versions. If you
exit emacs, all terminals should be restored to their previous states.
TIPS & TRICKS
-------------
I think the best way to use the new Emacs is to have it running inside
a disconnected GNU screen session, and always use emacsclient for
normal work. One advantage of this is that not a single keystroke of
your work will be lost if the display device that you are using
crashes, or the network connection times out, or whatever. (I had an
extremely unstable X server for some time while I was developing these
patches, and running Emacs this way has saved me a number of M-x
recover-session invocations.)
I use the following two bash scripts to handle my Emacs sessions:
-------------------------------------------------------connect-emacs--
#!/bin/bash
# Usage: connect-emacs <name> <args>...
#
# Connects to the Emacs instance called NAME. Starts up the instance
# if it is not already running. The rest of the arguments are passed
# to emacsclient.
name="$1"
shift
if [ -z "$name" ]; then
echo "Usage: connect_emacs <name> <args>..." >&2
exit 1
fi
preload-emacs "$name" wait
/usr/bin/emacsclient.emacs-multi-tty -s "$name" "$@"
----------------------------------------------------------------------
-------------------------------------------------------preload-emacs--
#!/bin/bash
# Usage: preload-emacs <name> [<waitp>]
#
# Preloads the Emacs instance called NAME in a detached screen
# session. Does nothing if the instance is already running. If WAITP
# is non-empty, the function waits until the server starts up and
# creates its socket; otherwise it returns immediately.
name="$1"
waitp="$2"
screendir="/var/run/screen/S-$USER"
if [ "${XDG_RUNTIME_DIR+set}" ]; then
serverdir="$XDG_RUNTIME_DIR/emacs"
else
serverdir="${TMPDIR-/tmp}/emacs$UID"
fi
emacs=/usr/bin/emacs-multi-tty # Or wherever you installed your multi-tty Emacs
if [ -z "$name" ]; then
echo "Usage: preload_emacs <name> [<waitp>]" >&2
exit 1
fi
if [ ! -e "$screendir"/*."$name" ]; then
if [ -e "$serverdir/$name" ]; then
# Delete leftover socket (for the wait option)
rm "$serverdir/$name"
fi
screen -dmS "$name" "$emacs" -nw --eval "(setq server-name \"$name\")" -f server-start
fi
if [ ! -z "$waitp" ]; then
while [ ! -e "$serverdir/$name" ]; do sleep 0.1; done
fi
----------------------------------------------------------------------
I have the following in my profile to have two instances automatically
preloaded for editing and email:
preload-emacs editor
preload-emacs gnus
It is useful to set up short aliases for connect-emacs. I use the
following:
alias edit="connect-emacs editor"
alias e=edit
alias et="connect-emacs editor -t"
alias gnus="connect-emacs gnus"
THINGS TO DO
------------
** See if 'tty-defined-color-alist' needs to be terminal-local.
Update: Dan says it should be, so convert it.
** Mikhail Gusarov suggest to add a hook akin to
'after-make-frame-functions' that is called whenever Emacs connects
to a new terminal. Good idea!
** emacsclient -t on the console does not work after su. You have to
use non-root accounts or start as root to see this.
Login: root
Password:
# su lorentey
$ emacsclient -t
*ERROR*: Could not open file: /dev/tty1
The tty can be opened as /dev/tty by emacsclient, but not by Emacs.
This seems to be a serious problem. Currently my only idea is to
bring back the ugly pty proxy hack from the initial versions of
multi-tty. Suggestions would be appreciated.
Update: we could change emacsclient to pass its open file
descriptor to the Emacs process. Unfortunately, this requires a
new Lisp-level Emacs API, and as file descriptors are not otherwise
exported to Lisp, this approach seems at least as ugly as the pty
proxy idea.
** lisp/vc.el depends on the terminal type during load time.
'vc-annotate-color-map' is one example that needs to be fixed.
** Understand how 'quit_throw_to_read_char' works, and fix any bugs
that come to light.
** See if getcjmp can be eliminated somehow. Why does Emacs allow
asynchronous input processing while it's reading input anyway?
** 'delete-frame' events are handled by 'special-event-map'
immediately when read by 'read_char'. This is fine but it prevents
higher-level keymaps from binding that event to get notified of the
deleted frame.
Sometimes it would be useful for Lisp code to be notified of frame
deletions after they have happened, usually because they want to
clean up after the deleted frame. Not all frame-local states can
be stored as a frame parameter. For example,
'display-splash-screen' uses 'recursive-edit' with a special keymap
override to create its buffer---and it leads to all kinds of
nastiness if Emacs stays in this recursive edit mode after the
frame containing the splash screen is deleted. Basically, the
splash-screen implementation wants to throw out of the recursive
edit when the frame is deleted; however, it is not legal to throw
from 'delete-frame-functions' because 'delete-frame' must not fail.
(Introducing 'delete-frame-after-functions' would not help either
because 'delete-frame' may not fail at that time either.)
Currently 'fancy-splash-screens' installs a
'delete-frame-functions' hook that sets up a timer to exit the
recursive edit. This is an adequate solution, but it would perhaps
be better to have something like a 'frame-deleted' event that could
be bound in the normal way.
** Trouble: 'setenv' doesn't actually set environment variables in the
Emacs process. This defeats the purpose of the elaborate
'server-with-environment' magic around the 'tgetent' call in
'init_tty'. D'oh.
** (Possibly) create hooks in struct device for creating frames on a
specific terminal, and eliminate the hackish terminal-related frame
parameters (display, tty, tty-type).
make_terminal_frame
create_tty_output
** Decide whether to keep the C implementation of terminal parameters,
or revert to the previous, purely Lisp code. It turned out that
local environments do not need terminal parameters after all.
** Move Fsend_string_to_terminal to term.c, and declare get_named_tty
as static, removing it from dispextern.h.
Move fatal to emacs.c and declare it somewhere.
** Search for 'suspend-emacs' references and replace them with
'suspend-frame', if necessary. Ditto for 'save-buffers-kill-emacs'
vs. 'save-buffers-kill-display'.
** Emacs crashes when a tty frame is resized so that there is no space
for all its windows. (Tom Schutzer-Weissmann)
** Report GTK multi-display problems to GTK maintainers. For extra
credit, fix them.
Currently you can not connect to new X displays when you compile
Emacs with GTK support. If you want to play around with GTK
multidisplay (and don't mind core dumps), you can edit src/config.h
and define HAVE_GTK_MULTIDISPLAY there by hand.
https://gitlab.gnome.org/GNOME/gtk/issues/221
Update: Han reports that GTK+ version 2.8.9 almost gets display
disconnects right. GTK will probably be fully fixed by the time
multi-tty gets into the trunk.
Update: I am still having problems with GTK+ 2.8.10. I have the
impression that the various multidisplay fixes will only get
released in GTK+ 2.10.
** Audit 'face-valid-attribute-values' usage in customize and
elsewhere. Its return value depends on the current window system.
Replace static initializers using it with runtime functions. For
example, custom's buttons are broken on non-initial device types.
** Possibly turn off the double C-g feature when there is an X frame.
C.f. (emacs)Emergency Escape.
** frames-on-display-list should also accept frames.
** Consider the 'tty-type' frame parameter and the 'display-tty-type'
function. They serve the exact same purpose. I think it may be
a good idea to eliminate one of them, preferably 'tty-type'.
** The handling of lisp/term/*.el, and frame creation in general, is a
big, big mess. How come the terminal-specific file is loaded by
tty-create-frame-with-faces? I don't think it is necessary to load
these files for each frame; once per terminal should be enough.
Update: lisp/term/*.el is not loaded repeatedly anymore, but
faces.el still needs to be cleaned up.
** Fix frame-set-background-mode in this branch. It was recently
changed in CVS, and frame.el in multi-tty has not yet been adapted
for the changes. (It needs to look at
default-frame-background-mode.) (Update: maybe it is fixed now;
needs testing.)
** I think '(set-)terminal-local-value' and the terminal parameter
mechanism should be integrated into a single framework.
(Update: '(set-)terminal-local-value' is now eliminated, but the
terminal-local variables should still be accessible as terminal
parameters. This also applies to 'display-name' and similar
functions.)
** Add the following hooks: after-delete-frame-hook (for server.el,
instead of delete-frame-functions),
after-delete-terminal-functions, after-create-terminal-functions.
** BULK RENAME: The 'display-' prefix of new Lisp-level functions
conflicts with stuff like 'display-time-mode'. Use 'device-'
or 'terminal-' instead. I think I prefer 'terminal-'.
It turns out that most of the offending Lisp functions were defined
in the trunk. Therefore, compatibility aliases should be defined
for the following names:
display-color-cells terminal-color-cells
display-color-p terminal-color-p
display-graphic-p terminal-graphic-p
display-grayscale-p terminal-grayscale-p
display-images-p terminal-images-p
display-mm-height terminal-mm-height
display-mm-width terminal-mm-width
display-mouse-p terminal-mouse-p
display-multi-font-p terminal-multi-font-p
display-multi-frame-p terminal-multi-frame-p
display-pixel-height terminal-pixel-height
display-pixel-width terminal-pixel-width
display-pixels-per-inch terminal-pixels-per-inch
display-planes terminal-planes
display-popup-menus-p terminal-popup-menus-p
display-save-under terminal-save-under
display-screens terminal-screens
display-supports-face-attributes-p terminal-supports-face-attributes-p
display-visual-class terminal-visual-class
framep-on-display framep-on-terminal
frames-on-display-list frames-on-terminal-list
The following functions were introduced in the multi-tty branch, and
were renamed without aliases:
delete-display delete-terminal
display-controlling-tty-p controlling-tty-p
display-list terminal-list
display-live-p terminal-live-p
display-name terminal-name
display-tty-type tty-type
frame-display frame-terminal
selected-display selected-terminal
** The single-keyboard mode of MULTI_KBOARD is extremely confusing
sometimes; Emacs does not respond to stimuli from other keyboards.
At least a beep or a message would be important, if the single-mode
is still required to prevent interference. (Reported by Dan
Nicolaescu.)
Update: selecting a region with the mouse enables single_kboard
under X. This is very confusing.
Update: After discussions with Richard Stallman, this will be
resolved by having locked displays warn the user to wait, and
introducing a complex protocol to remotely bail out of
single-kboard mode by pressing C-g.
Update: Warning the user is not trivial to implement, as Emacs has
only one echo area, shared by all frames. Ideally the warning
should not be displayed on the display that is locking the others.
Perhaps the high probability of user confusion caused by
single_kboard mode deserves a special case in the display code.
Alternatively, it might be good enough to signal single_kboard mode
by changing the modelines or some other frame-local display element
on the locked out displays.
Update: In fact struct kboard does have an echo_string slot.
** The session management module is prone to crashes when the X
connection is closed and then later I try to connect to a new X
session:
#0 0xb7ebc806 in SmcGetIceConnection () from /usr/X11R6/lib/libSM.so.6
#1 0x080e6641 in x_session_check_input (bufp=0xbf86c9c0) at xsmfns.c:144
#2 0x080d3bbc in XTread_socket (device=0xa722ff8, expected=1, hold_quit=0xbf86ca90) at xterm.c:7037
#3 0x080fa404 in read_avail_input (expected=1) at keyboard.c:6696
#4 0x080fa4ca in handle_async_input () at keyboard.c:6900
#5 0x080d51fa in x_term_init (display_name=162628899, xrm_option=0x0, resource_name=0x857068c "emacs") at xterm.c:10622
#6 0x080d920e in x_display_info_for_name (name=162628899) at xfns.c:3975
#7 0x080d92f9 in check_x_display_info (object=1) at xfns.c:274
#8 0x080d97b8 in Fx_create_frame (parms=151221485) at xfns.c:3016
#9 0x0815bf72 in Ffuncall (nargs=2, args=0xbf86ceec) at eval.c:2851
I installed a workaround to prevent this. The X session manager is
only contacted when the very first display in the Emacs session is
an X display. Also, x_delete_display() on this display aborts
session management, and XTread_socket only calls
x_session_check_input when it is called for the display that the
session was opened on. While this does not really fix the bug, it
makes it much less frequent, because session manager support will
not normally be enabled when Emacs can survive the shutdown of the
X server.
See if xsmfns.c should be updated.
** Hunt down display-related functions in frame.el and extend them all
to accept display ids.
** rif->flush_display_optional (NULL) calls should be replaced by a
new global function.
** The set-locale-environment hack (adding the DISPLAY option) should
be replaced with a clean design.
** standard-display-table should be display-local.
standard-display-european should be display-local.
** With iswitchb-default-method set to 'always-frame, only frames on
the current display should be considered. This might involve
extending 'get-buffer-window'.
** Have a look at Vlocale_coding_system. Seems like it would be a
tedious job to localize it, although most references use it for
interfacing with libc and are therefore OK with the global
definition.
Exceptions found so far: x-select-text and
x-selection-value (old name: x-cut-buffer-or-selection-value).
** Have a look at fatal_error_hook.
** Have a look at set_frame_matrix_frame.
** Check if we got term-setup-hook right.
** I think tip_frame should be display-local.
** Check display reference count handling in x_create_tip_frame.
** make-frame does not correctly handle extra parameters in its
argument:
(frame-parameter (make-frame (list (cons 'foobar 42))) 'foobar)
=> nil
(This is likely an error in the CVS trunk.)
** Gergely Nagy suggests that C-x # should only kill the current
frame, not any other emacsclient frame that may have the same file
opened for editing. I think I agree with him.
** Very strange bug: visible-bell does not work on secondary
terminals in xterm and konsole. The screen does flicker a bit,
but it's so quick it isn't noticeable.
(Update: This is probably some problem with padding or whatnot on
the secondary terminals.)
** Move baud_rate to struct display.
** Implement support for starting an interactive Emacs session without
an initial frame. (The user would connect to it and open frames
later, with emacsclient.)
** Implement Mac/Windows/DOS support. Many XXX comments mark things
that probably need updating, ChangeLogs will help in spotting
changes to X specific files that may need porting.
** Do a grep on XXX and ?? for more issues.
** flow-ctrl.el must be updated.
** Fix stuff_char for multi-tty. Doesn't seem to be of high priority.
DIARY OF CHANGES
----------------
(ex-TODO items with explanations.)
-- Introduce a new struct for terminal devices.
(Done, see struct tty_output. The list of members is not yet
complete.)
-- Change the bootstrap procedure to initialize tty_list.
(Done, but needs review.)
-- Change make-terminal-frame to support specifying another tty.
(Done, new frame parameters: 'tty' and 'tty-type'.)
-- Implement support for reading from multiple terminals.
(Done, read_avail_input tries to read from each terminal, until one
succeeds. MULTI_KBOARD is not used. Secondary terminals don't send
SIGIO!)
(Update: They do, now.)
(Update2: After enabling X, they don't.)
-- other-frame should cycle through the frames on the 'current'
terminal only.
(Done, by trivially modifying next_frame and prev_frame.)
-- Support different terminal sizes.
(Done, no problem.)
-- Make sure terminal resizes are handled gracefully. (Could be
problematic.)
(Done. We don't get automatic SIGWINCH for additional ttys,
though.)
-- Extend emacsclient to automatically open a new tty when it connects
to Emacs.
(Done. It's an ugly hack, needs more work.)
-- Redisplay must refresh the topmost frame on *all* terminals, not
just the initial terminal.
(Done, but introduced an ugly redisplay problems. Ugh.)
-- Fix redisplay problems.
(Done; it turned out that the entire Wcm structure must be moved
inside tty_output. Why didn't I catch this earlier?)
-- Provide a way for emacsclient to tell Emacs that the tty has been
resized.
(Done, simply forward the SIGWINCH signal.)
-- Each keypress should automatically select the frame corresponding
to the terminal that it was coming from. This means that Emacs
must know from which terminal the last keyboard event came from.
(Done, it was quite simple, the input event system already
supported multiple frames.)
-- Fix SIGIO issue with secondary terminals.
(Done, emacsclient signals Emacs after writing to the proxy pseudo
terminal. Note that this means that multi-tty does not work with
raw ttys!)
(Update: This is bullshit. There is a read_input_waiting function,
extend that somehow.)
(Update of update: The first update was not right either, extending
read_input_waiting was not necessary. Secondary ttys do seem to
send signals on input.)
(Update^3: Not any more.)
-- Make make-terminal-frame look up the 'tty' and 'tty-type' frame
parameters from the currently selected terminal before the global
default.
(Done.)
-- Put all cached terminal escape sequences into struct tty_output.
Currently, they are still stored in global variables, so we don't
really support multiple terminal types.
(Done. It was not fun.)
-- Implement sane error handling after initialization. (Currently
emacs exits if you specify a bad terminal type.) The helpful error
messages must still be provided when Emacs starts.
(Done.)
-- Implement terminal deletion, i.e., deleting local frames, closing
the tty device and restoring its previous state without exiting
Emacs.
(Done, but at the moment only called when an error happens during
initialization. There is a memory corruption error around this
somewhere.) (Update: now it is fully enabled.)
-- Implement automatic deletion of terminals when the last frame on
that terminal is closed.
(Done.)
-- Restore tty screen after closing the terminal.
(Done, we do the same as Emacs 21.2 for all terminals.)
-- 'TERM=dumb src/emacs' does not restore the terminal state.
(Done.)
-- C-g should work on secondary terminals.
(Done, but the binding is not configurable.)
-- Deal with SIGHUP in Emacs and in emacsclient. (After this, the
server-frames may be removed from server.el.)
(Done, nothing to do. It seems that Emacs does not receive SIGHUP
from secondary ttys, which is actually a good thing.) (Update: I
think it would be a bad idea to remove server-frames.)
-- Change emacsclient/server.el to support the -t argument better,
i.e. automatically close the socket when the frame is closed.
(Seems to be working OK.)
-- Fix mysterious memory corruption error with tty deletion. To
trigger it, try the following shell command:
while true; do TERM=no-such-terminal-definition emacsclient -h; done
Emacs usually dumps core after a few dozen iterations. (The bug
seems to be related to the xfreeing or bzeroing of
tty_output.Wcm. Maybe there are outside references to struct Wcm?
Why were these vars collected into a struct before multi-tty
support?)
(Done. Whew. It turned out that the problem had nothing to do
with hypothetical external references to Wcm, or any other
tty_output component; it was simply that delete_tty closed the
filehandles of secondary ttys twice, resulting in fclose doubly
freeing memory. Utterly trivial matter. I love the C's memory
management, it puts hair on your chest.)
-- Support raw secondary terminals. (Note that SIGIO works only on
the controlling terminal.) Hint: extend read_input_waiting for
multiple ttys and hopefully this will be fixed.
(Done, it seems to have been working already for some time. It
seems F_SETOWN does work, after all. Not sure what made it fail
earlier, but it seems to be fixed (there were several changes
around request_sigio, maybe one of them did it).
read_input_waiting is only used in sys_select, don't change
it.) (Update: After adding X support, it's broken again.)
(Update^2: No it isn't.) :-)
-- Find out why does Emacs abort when it wants to close its
controlling tty. Hint: chan_process[] array. Hey, maybe
noninterrupt-IO would work, too? Update: no, there is no process
for stdin/out.
(Done. Added add/delete_keyboard_wait_descriptor to
term_init/delete_tty. The hint was right, in a way.)
-- Issue with SIGIO: it needs to be disabled during redisplay. See if
fcntl kernel behavior could be emulated by emacsclient.
(Done. Simply disabled the SIGIO emulation hack in emacsclient.)
(Update: it was added back.) (Update^2: and removed again.)
-- server.el: There are issues with saving files in buffers of closed
clients. Try editing a file with emacsclient -f, and (without
saving it) do a delete-frame. The frame is closed without
question, and a surprising confirmation prompt appears in another
frame.
(Done. delete-frame now asks for confirmation if it still has
pending buffers, and modified buffers don't seem to be deleted.)
-- emacsclient.el, server.el: Handle eval or file open errors when
doing -t.
(Done.)
-- Make parts of struct tty_output accessible from Lisp. The device
name and the type is sufficient.
(Done, see frame-tty-name and frame-tty-type.)
-- Export delete_tty to the Lisp environment, for emacsclient.
(Done, see delete-tty.)
-- Get rid of the accessor macros in termchar.h, or define macros for
all members.
(Done.)
-- Move device-specific parameters (like costs) commonly used by
device backends to a common, device-dependent structure.
(Done. See struct display_method in termhooks.h.)
-- Fix X support.
(Done. Well, it seems to be working.)
-- Allow simultaneous X and tty frames. (Handling input could be
tricky. Or maybe not.)
(Done. Allowed, that is. It is currently extremely unstable, to
the point of being unusable. The rif variable causes constant
core dumps. Handling input is indeed tricky.)
-- Rewrite multi-tty input in terms of MULTI_KBOARD.
(Done. In fact, there was no need to rewrite anything, I just
added a kboard member to tty_display_info, and initialized the
frame's kboard from there.)
-- Fix rif issue with X-tty combo sessions. IMHO the best thing to do
is to get rid of that global variable (and use the value in
display_method, which is guaranteed to be correct).
(Done, did exactly that. Core dumps during combo sessions became
much rarer. In fact, I have not yet met a single one.)
-- Add multi-tty support to talk.el.
(Done.)
-- Clean up the source of emacsclient. It is a mess.
(Done, eliminated stupid proxy-pty kludge.)
-- Fix faces on tty frames during X-tty combo sessions. There is an
init_frame_faces call in init_sys_modes, see if there is a problem
with it.
(Done, there was a stupid mistake in
Ftty_supports_face_attributes_p. Colors are broken, though.)
-- C-x 5 2, C-x 5 o, C-x 5 0 on an emacsclient frame unexpectedly
exits emacsclient. This is a result of trying to be clever with
delete-frame-functions.
(Fixed, added delete-tty-after-functions, and changed server.el to
use it.)
-- Something with (maybe) multi-keyboard support broke function keys
and arrows on ttys during X+tty combo sessions. Debug this.
(I can't reproduce it, maybe the terminal type was wrong.)
-- Fix input from raw ttys (again).
(Now it seems to work all right.)
-- During an X-tty combo session, a (message "Hello") from a tty frame
goes to the X frame. Fix this.
(Done. There was a safeguard against writing to the initial
terminal frame during bootstrap which prevented echo_area_display
from working correctly on a tty frame during a combo session.)
-- If there are no frames on its controlling terminal, Emacs should
exit if the user presses C-c there.
(Done, as far as possible. See the SIGTERM comment in
interrupt_signal on why this seems to be impossible to solve this
in general.)
-- During an X session, Emacs seems to read from stdin. Also, Emacs
fails to start without a controlling tty.
(Fixed by replacing the troublesome termcap display with a dummy
bootstrap display during bootstrap.
-- Do tty output through struct display, like graphical display
backends.
(Done.)
-- Define an output_initial value for output_method for the initial
frame that is dumped with Emacs. Checking for this frame (e.g. in
cmd_error_internal) is ugly.
(Done, breaking interactive temacs.)
-- The command "emacsclient -t -e '(delete-frame)'" fails to exit.
(Fixed.)
-- frame-creation-function should always create a frame that is on the
same display as the selected frame. Maybe frame-creation-function
should simply be removed and make-frame changed to do the right
thing.
(Done, with a nice hack. frame-creation-function is now frame-local.)
-- Fix C-g on raw ttys.
(Done. I disabled the interrupt/quit keys on all secondary
terminals, so Emacs sees C-g as normal input. This looks like an
overkill, because emacsclient has extra code to pass SIGINT to
Emacs, so C-g should remain the interrupt/quit key on emacsclient
frames. See the next entry why implementing this distinction would
be a bad idea.)
-- Make sure C-g goes to the right frame with ttys. This is hard, as
SIGINT doesn't have a tty parameter. :-(
(Done, the previous change fixes this as a pleasant side effect.)
-- I have seen a case when Emacs with multiple ttys fell into a loop
eating 100% of CPU time. Strace showed this loop:
getpid() = 30284
kill(30284, SIGIO) = 0
--- SIGIO (I/O possible) @ 0 (0) ---
ioctl(6, FIONREAD, [0]) = -1 EIO (Input/output error)
ioctl(5, FIONREAD, [0]) = -1 EIO (Input/output error)
ioctl(0, FIONREAD, [0]) = 0
sigreturn() = ? (mask now [])
gettimeofday({1072842297, 747760}, NULL) = 0
gettimeofday({1072842297, 747806}, NULL) = 0
select(9, [0 3 5 6], NULL, NULL, {0, 0}) = 2 (in [5 6], left {0, 0})
select(9, [0 3 5 6], NULL, NULL, {0, 0}) = 2 (in [5 6], left {0, 0})
gettimeofday({1072842297, 748245}, NULL) = 0
I have seen something similar with a single X frame, but have not
been able to reproduce it for debugging.
Update: This may have been caused by checking for nread != 0
instead of nread > 0 after calling read_socket_hook in
read_avail_input.
(Fixed. This was caused by unconditionally including stdin in
input_wait_mask in init_process_emacs. The select call in
wait_reading_process_input always returned immediately, indicating
that there is pending input from stdin, which nobody read.
Note that the above strace output seems to be an unrelated but
similar bug. I think that is now fixed.)
-- Exiting Emacs while there are emacsclient frames doesn't restore the
ttys to their default states.
(This seems to be fixed by some previous change.)
-- Allow opening an X session after -nw.
(Done.)
-- Fix color handling during tty+X combo sessions. (It seems that tty
sessions automatically convert the face colors to terminal colors
when the face is loaded. This conversion must happen instead on
the fly in write_glyphs, which might be problematic, as color
approximation is currently done in lisp (term/tty-colors.el).)
(Update: hm, colors seem to work fine if I start emacs with -nw and
then create an X frame. Maybe it's just a small buglet somewhere.)
(Seems to be fixed. The problem was in startup.el, it did not
initialize tty colors when the initial window system was
graphical.)
-- emacs -nw --eval '(y-or-n-p "Foobar")' segfaults. (Reported by
Romain Francoise)
(Fixed, there was a keyboard initialization problem.)
-- Fix interactive use of temacs. There are face-related SEGVs, most
likely because of changes in realize_default_face, realize_face.
(Fixed.)
-- Don't exit Emacs when the last X connection fails during a
multi-display session.
(Fixed.)
-- Dan Nicolaescu noticed that starting emacsclient on the same
terminal device that is the controlling tty of the Emacs process
gives unexpected results.
(Fixed.)
-- Istvan Marko reported that Emacs hang on ttys if it was started
from a shell script.
(Fixed. There was a bug in the multi-tty version of
narrow_foreground_group. tcsetpgrp blocks if it is called from a
process that is not in the same process group as the tty.)
-- emacsclient -t from an Emacs term buffer does not work, complains
about face problems. This can even lock up Emacs (if the recursive
frame sets single_kboard). Update: the face problems are caused by
bugs in term.el, not in multi-tty. The lockup is caused by
single_kboard mode, and is not easily resolvable. The best thing to
do is to simply refuse to create a tty frame of type 'eterm'.
(Fixed, changed emacsclient to check for TERM=eterm. The face
complaints seem to be caused by bugs in term.el; they are not
related to multi-tty.)
-- Find out the best way to support suspending Emacs with multiple
ttys. My guess: disable it on the controlling tty, but from other
ttys pass it on to emacsclient somehow. (It is (I hope) trivial to
extend emacsclient to handle suspend/resume. A 'kill -STOP' almost
works right now.)
(Done. I needed to play with signal handling and the server
protocol a bit to make emacsclient behave as a normal UNIX program
wrt foreground/background process groups.)
-- There is a flicker during the startup of 'emacs -nw'; it's as if
the terminal is initialized, reset and then initialized again.
Debug this. (Hint: narrow_foreground_group is called twice during
startup.)
(This is gone.)
-- Robert Chassell has found serious copy-paste bugs with the
multi-tty branch. There seem to be redisplay bugs while copying
from X to a terminal frame. Copying accented characters do not
work for me.
(Patch-124 should fix this, by changing the interprogram-*-function
variables to be frame-local, as suggested by Mark Plaksin
(thanks!). I think that the redisplay bugs are in fact not bugs,
but delays caused by single_kboard --> perhaps MULTI_KBOARD should
be removed.)
-- frame-creation-function was removed, which might be a bad idea.
Think up a compatible solution.
(It was an internal interface that may be changed when necessary.)
-- Change Lisp code not to (getenv "TERM"); use the 'tty-type' frame
parameter or the frame-tty-type function instead. (M-x tags-search
"TERM" helps with this.) Update: Actually, all getenv invocations
should be checked for multi-tty compatibility, and an interface
must be implemented to get the remote client's environment.
(Done. Only getenv calls in lisp/term/*.el were changed; other
calls should be mostly left as they are.)
-- Add an elaborate mechanism for display-local variables. (There are
already a few of these; search for 'terminal-local' in the Elisp
manual.)
(Not needed. Display-local variables could be emulated by
frame-local variables.)
-- Emacs assumes that all terminal frames have the same locale
settings as Emacs itself. This may lead to bogus results in a
multi-locale setup. (E.g., while logging in from a remote client
with a different locale.)
(Update after new bugreport by Friedrich Delgado Friedrichs:
(at least) the structs terminal_coding and keyboard_coding in
coding.c must be moved to struct display, and the Lisp interface
[set-]keyboard-coding-system must be adapted for the change.)
(Fixed. Emacs now uses the locale settings as seen by the
emacsclient process for server tty frames.)
(Update: Not really; Vlocale_coding_system is still global.)
-- Make 'struct display' accessible to Lisp programs. Accessor functions:
(displayp OBJECT): Returns t if OBJECT is a display.
=> Implemented as display-live-p.
(display-list): Returns list of currently active displays.
=> Implemented.
(selected-display): Returns the display object of the selected frame.
=> Not strictly necessary, but implemented anyway.
(frame-display FRAME): Returns the display object of FRAME.
=> Implemented.
(display-frames DISPLAY): Returns a list of frames on DISPLAY.
=> Already implemented, see frames-on-display-list.
(display-type DISPLAY): Returns the type of DISPLAY, as a
symbol. (See 'framep'.)
=> Implemented as display-live-p.
(display-device DISPLAY): Returns the name of the device that
DISPLAY uses, as a string. (E.g: "/dev/pts/16", or
":0.0")
=> Implemented as display-name.
etc.
See next issue why this is necessary.
(Update: The consensus on emacs-devel seems to be to do this via
integer identifiers. That's fine by me.)
(Done.)
-- The following needs to be supported:
$ emacsclient -t
C-z
$ emacsclient -t
(This fails now.)
The cleanest way to solve this is to allow multiple displays on the
same terminal device; each new emacsclient process should create
its own display. As displays are currently identified by their
device names, this is not possible until struct display becomes
accessible as a Lisp-level object.
(Done.)
-- Support multiple character locales. A version of
'set-locale-environment' needs to be written for setting up
display-local settings on ttys. I think calling
set-display-table-and-terminal-coding-system and
set-keyboard-coding-system would be enough. The language
environment itself should remain a global setting.
(Done, by an ugly hack.)
-- The terminal customization files in term/*.el tend to change global
parameters, which may confuse Emacs with multiple displays. Change
them to tweak only frame-local settings, if possible. (They tend
to call define-key to set function key sequences a lot.)
(Done, by making 'function-key-map' terminal-local (i.e., part of
struct kboard). This has probably covered all the remaining problems.)
-- xt-mouse.el needs to be adapted for multi-tty. It currently
signals an error on kill-emacs under X, which prevents the user
from exiting Emacs. (Reported by Mnemonikk on freenode.)
(Done, I hope.)
-- Having {reset,init}_all_sys_modes in set-input-mode breaks arrow
keys on non-selected terminals under screen, and sometimes on other
terminal types as well. The other function keys continue to work
fine. Sometimes faces on these screens become garbled.
This only seems to affect displays that are of the same terminfo
type as the selected one. Interestingly, in screen Emacs normally
reports the up arrow key as 'M-o A', but after the above SNAFU, it
complains about 'M-[ a'. UNIX ttys are a complete mystery to me,
but it seems the reset-reinitialize cycle somehow leaves the
non-selected terminals in a different state than usual. I have no
idea how this could happen.
Currently set-input-mode resets only the currently selected
terminal, which seems to somehow work around the problem.
Update:
Dan Nicolaescu <dann@ics.uci.edu> writes:
> Some terminals have 2 modes for cursor keys: Application Mode where
> the cursor keys transmit the codes defined in the terminfo entry, and
> Cursor mode. Applications have to send the smkx and rmkx terminfo
> strings to switch between the 2 modes. So Emacs (and emacsclient) have
> to send smkx when initializing and rmkx when quitting (or on
> suspend).
(I think patch-370 fixed this.)
-- This long-standing bug (first reported by Han Boetes) seems to come
and go all the time. It is time to track it down and fix it.
emacs
M-x server-start
# From another xterm:
emacsclient -e '(y-or-n-p "Do you want me to crash? ")'
# Notice how the answer ends up in the *scratch* buffer
M-x garbage-collect
SIGSEGV
(Fixed in patch-414 after detailed analysis by Kalle Olavi Niemitalo.)
-- normal-erase-is-backspace-mode in simple.el needs to be updated for
multi-tty (rep. by Dan Waber). (The Delete key is broken on X
because of this.)
(Fixed in patch-427.)
-- I think keyboard-translate-table should be made terminal-local.
(Done in patch-431.)
-- The semantics of terminal-local variables are confusing; it is not
clear what binding is in effect in any given time. See if
current_kboard (or at least the terminal-local bindings exported to
Lisp) might be changed to be tied to the selected frame instead.
Currently, 'function-key-map' and 'key-translation-map' may be
accessed reliably only using the hackish
'(set-)terminal-local-value' functions.
Perhaps there should be a difference between 'last-command' &co.
and these more conventional configuration variables.
(E.g. 'symbol-value' would use current_kboard to access
'last-command', but SELECTED_FRAME()->display->kboard to get the
value of 'function-key-map'.
(Fixed in patch-434.)
-- If the first key pressed on a new tty terminal is a function key,
it is not recognized correctly. May be related to the bug below.
(Seems to have been fixed as a side effect of patch-434. "The bug
below" was the set-input-mode madness.)
(Update: this bug was fixed for good in patch-449. It was tracked
down to a bug in 'read_key_sequence': it failed to reinitialize its
local function-key-map/key-translation-map references when it
switched keyboards. I don't understand why did this bug only
appear on brand new frames, though!)
-- Disable connecting to a new X display when we use the GTK toolkit.
(Disabled in patch-450.)
-- Implement automatic forwarding of client environment variables to
forked processes, as discussed on the multi-tty list. Terminal
parameters are now accessible in C code, so the biggest obstacle is
gone. The 'getenv_internal' and 'child_setup' functions in
callproc.c must be changed to support the following variable:
terminal-local-environment-variables is a variable defined in ...
Enable or disable terminal-local environment variables.
If set to t, 'getenv', 'setenv' and subprocess creation
functions use the environment variables of the emacsclient
process that created the selected frame, ignoring
'process-environment'.
If set to nil, Emacs uses 'process-environment' and ignores
the client environment.
Otherwise, 'terminal-local-environment-variables' should be a
list of variable names (represented by Lisp strings) to look
up in the client environment. The rest will come from
'process-environment'.
(Implemented in patch-461; 'terminal-getenv', 'terminal-setenv' and
'with-terminal-environment' are now replaced by extensions to
'getenv' and 'setenv', and the new 'local-environment-variables'
facility. Yay!)
(Updated in patch-465 to fix the semantics of let-binding
'process-environment'. 'process-environment' was changed to
override all local/global environment variables, and a new variable
'global-environment' was introduced to have 'process-environment's
old meaning.)
(Updated in patch-466 to fix the case when two emacsclient sessions
share the same terminal, but have different environment. The local
environment lists are now stored as frame parameters, so the
C-level terminal parameters are not strictly necessary any more.)
-- 'Fdelete_frame' is called from various critical places where it is
not acceptable for the frame deletion to fail, e.g. from
x_connection_closed after an X error. 'Fdelete_frame' now protects
against 'delete-frame-functions' throwing an error and preventing a
frame delete. (patch-475)
-- Fix set-input-mode for multi-tty. It's a truly horrible interface;
what if we'd blow it up into several separate functions (with a
compatibility definition)?
(Done. See 'set-input-interrupt-mode', 'set-output-flow-control',
'set-input-meta-mode' and 'set-quit-char'.) (patch-457)
-- Let-binding 'overriding-terminal-local-map' on a brand new frame
does not seem to work correctly. (See 'fancy-splash-screens'.)
The keymap seems to be set up right, but events go to another
terminal. Or is it 'unread-command-events' that gets Emacs
confused? Investigate.
(Emacs was confused because a process filter entered
'recursive-edit' while Emacs was reading input. I added support
for this in the input system.) (patch-489)
-- I smell something funny around pop_kboard's "deleted kboard" case.
Determine what are the circumstances of this case, and fix any
bug that comes to light.
(It happens simply because single_kboard's terminal is sometimes
deleted while executing a command on it, for example the one that
kills the terminal. There was no bug here, but I rewrote the whole
single_kboard mess anyway.) (patch-489)
-- Understand Emacs's low-level input system (it's black magic) :-)
What exactly does interrupt_input do? I tried to disable it for
raw secondary tty support, but it does not seem to do anything
useful. (Update: Look again. X unconditionally enables this, maybe
that's why raw terminal support is broken again. I really do need
to understand input.)
(Update: I am starting to understand the read_key_sequence->read-char
->kbd_buffer_get_event->read_avail_input->read_socket_hook path. Yay!)
(Update: OK, it all seems so easy now (NOT). Input could be done
synchronously (with wait_reading_process_input), or asynchronously
by SIGIO or polling (SIGALRM). C-g either sets the Vquit_flag,
signals a 'quit condition, or throws to 'getcjmp' when Emacs was
waiting for input when the C-g event arrived.)
-- Replace wrong_kboard_jmpbuf with a special return value of
read_char. It is absurd that we use setjmp/longjmp just to return
to the immediate caller.
(Done in patch-500.)
-- 'tool-bar-mode', 'scroll-bar-mode', 'menu-bar-mode' and
'fringe-mode' are modes global to the entire Emacs session, not
just a single frame or a single terminal. This means that their
status sometimes differs from what's actually displayed on the
screen. As a consequence, the Options | Show/Hide menu sometimes
shows incorrect status, and you have to select an option twice for
it to have any visible effect on the current frame.
Change Emacs so that the status of the items in the Options |
Show/Hide menu correspond to the current frame.
(Done in patch-537.)
-- The 'default-directory' variable should somehow be set to the
cwd of the emacsclient process when the user runs emacsclient
without file arguments. Perhaps it is OK to just override the
directory of the *scratch* buffer.
(Done in patch-539.)
-- The borders on tooltip frames on X are messed up. More
specifically, the frame's internal border (internal-border-width
frame parameter) is not filled with the correct background color.
It seems the border contents are drawn onto by the
update_single_window call in 'x-show-tip'. After some debugging, I
think the window's background color is not set up
correctly---calling 'x_clear_area' fills the specified area with
black, not light yellow.
(Done in patch-544. A background_pixel field was defined both in
struct frame and struct x_output, and Emacs got confused between
them.)
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