Fix Delete key on X by adapting normal-erase-is-backspace-mode for multi-tty. (Report...

[bpt/emacs.git] / README.multi-tty

                        -*- coding: utf-8; mode: text; -*-
GOAL
----

This branch implements support for opening multiple, different tty
devices and simultaneous X and tty frames from a single Emacs session.

Some use cases:
Emacs is notoriously slow at startup, so most people use another
editor or emacsclient for quick editing jobs from the console.
Unfortunately, emacsclient was very awkward to use, because it did not
support opening a new Emacs frame on the current virtual console.
Now, with multi-tty support, it can do that.  (Emacsclient starts up
faster than vi!)

Some Gnus users (including me) run Gnus in an X frame in its own Emacs
instance, which they typically leave running for weeks.  It would be
nice if they could connect to this instance from a remote ssh session
and check their messages without opening a remote X frame or resorting
to gnus-slave.

WHO IS DOING IT
---------------

I'm Károly Lőrentey.  My address: lorentey@elte.hu.

Comments, bug reports, suggestions and patches are welcome; send them
to multi-tty@lists.fnord.hu.

The following is a (sadly incomplete) list of people who have
contributed to the project by testing, submitting patches, bug
reports, and suggestions.  Thanks!

ARISAWA Akihiro <ari@mbf.ocn.ne.jp>
Vincent Bernat <bernat@luffy.cx>
Han Boetes <han@mijncomputer.nl>
Robert J. Chassell <bob@rattlesnake.com>
Romain Francoise <romain@orebokech.com>
Ami Fischman <ami@fischman.org>
Friedrich Delgado Friedrichs <friedel@nomaden.org>
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>
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>
Francisco Borges <borges@let.rug.nl>
Frank Ruell <stoerte@dreamwarrior.net>
Dan Waber <dwaber@logolalia.com>
and many others.

Richard Stallman was kind enough to review an earlier version of my
patches.


MAILING LISTS
-------------

The multi-tty mailing list (discussion & bug reports):

        Address:        multi-tty@lists.fnord.hu
        Signup:         http://lists.fnord.hu/mailman/listinfo/multi-tty
        Archive:        http://news.gmane.org/gmane.emacs.multi-tty/

Commit notifications (read-only):

        Address:        multi-tty-commits@lists.fnord.hu
        Signup:         http://lists.fnord.hu/mailman/listinfo/multi-tty-commits


STATUS
------

The branch is now very stable and almost full-featured.  All of the
major problems have been fixed, only a few minor issues remain.  (It
still needs to be ported to Windows/Mac/DOS, though.)  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 open new Emacs frames by default.

The multi-tty branch has been scheduled for inclusion in the next
major release of Emacs (version 23).  I expect the merge into the
development trunk to occur sometime during next year (2005), after the
merge of the Unicode branch.

Tested on GNU/Linux, Solaris 8, FreeBSD and OpenBSD.  Please let me
know if you succeed or fail to use it on other platforms---I'll have a
few tricky test cases for you.

Known problems:

        * GTK support.  If you compile your Emacs with the GTK
          toolkit, some functionality of multi-tty will be lost.
          In particular, closing an X display causes a crash.
          Current releases of GTK have limitations and bugs that
          prevent full-blown multi-display support in Emacs.  Use the
          Lucid toolkit if you want to see a complete feature set.

        * 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 behaviour 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.

        * Mac, Windows and DOS support is broken, doesn't even
          compile.  Multiple display support will probably not provide
          new Emacs features on these systems, but the multi-tty
          branch changed a few low-level interfaces, and the
          system-dependent source files need to be adapted
          accordingly.  The changes are mostly trivial, so almost
          anyone can help, if only by compiling the branch and
          reporting the compiler errors.  (It is not worth to do this
          yet, though.)


HOW TO GET THE BRANCH
---------------------

The branch uses GNU Arch (http://www.gnuarch.org) for version control.

Retrieving the latest version of the branch:

        tla register-archive -f http://lorentey.hu/arch/2004/
        tla get lorentey@elte.hu--2004/emacs--multi-tty <directory>

This incantation uses my private archive mirror that is hosted on a
relatively low-bandwidth site; if you are outside Hungary, you will
probably want to you use my secondary mirror: (Note that the -f option
will overwrite the archive location if you have previously registered
the Hungarian one.)

        tla register-archive -f http://aszt.inf.elte.hu/~lorentey/mirror/arch/2004
        tla get lorentey@elte.hu--2004/emacs--multi-tty <directory>

        http://aszt.inf.elte.hu/~lorentey/mirror/arch/2004

The Arch supermirror provides mirroring services for all public Arch
repositories.  We have a mirror there, too, if you prefer.

        tla register-archive -f http://mirrors.sourcecontrol.net/lorentey%40elte.hu--2004
        tla get lorentey@elte.hu--2004/emacs--multi-tty <directory>

My GPG key id is 0FB27A3F; it is available from
hkp://wwwkeys.eu.pgp.net/, or from my homepage at
http://lorentey.hu/rolam/gpg.html)

Don't worry if the above checkout takes a few minutes to complete;
once you have a source tree, updating it to the latest revision will
be _much_ faster.  Use the following command for the update:

        tla replay

You can find more information about Arch on http://wiki.gnuarch.org/.
It's a wonderful source control system, I highly recommend it.

If you don't have tla, the branch has a homepage from which you can
download conventional patches against Emacs CVS HEAD:

        http://lorentey.hu/project/emacs.html

DEBIAN PACKAGES
---------------

If you run Debian, or a distribution based on Debian, you are welcome
to use our binary packages; put these lines in your /etc/apt/sources.list:

        # Multi-tty Emacs
        deb http://aszt.inf.elte.hu/~lorentey/mirror/apt ./
        deb-src http://aszt.inf.elte.hu/~lorentey/mirror/apt ./

Note that these packages are intended solely to provide an easy way to
test the new multi-tty features.  They are not to be taken as Emacs
releases, and it's a mistake to expect robust operation or any kind of
timely support for them.  Do not install them, unless you'd like to
have your editor crash on you.


COMPILATION
-----------

The multi-tty branch is compiled the same way as Emacs itself:

        make maintainer-clean  # (If you have compiled Emacs before)

        ./configure <your favourite options>
        make bootstrap
        make install

If you have strange compilation errors, they may be caused by old
*.elc files that are left over from an earlier bootstrap.  The `make
maintainer-clean' target deletes them, so it is a good idea to run
that before reporting a bug.  (Emacs requires a clean recompilation
after certain kinds of source code changes.)

TESTING
-------

To test the multi-tty branch, 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 works, and they
behave the same way as in previous Emacs versions.  If you exit emacs,
all terminals should be restored to their previous states.

This is work in progress, and probably full of bugs.  It is a good
idea to run emacs from gdb, so that you'll have a live instance to
debug if something goes wrong.  Please send me your bug reports on our
mailing list: multi-tty@lists.fnord.hu

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"
serverdir="/tmp/emacs$UID"
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"


CHANGELOG
---------

See arch logs.


NEWS
----

For the NEWS file:  (Needs much, much work)

** Support for multiple terminal devices has been added.

*** You can specify a terminal device (`tty' parameter) and a terminal
    type (`tty-type' parameter) to `make-terminal-frame'.

*** You can test for the presence of multiple terminal support by
    testing for the `multi-tty' feature.

*** Emacsclient has been extended to support opening a new terminal
    frame. Its behaviour has been changed to open a new Emacs frame by
    default.  Use the -c option to get the old behavior of opening
    files in the currently selected Emacs frame.

*** A make-frame-on-tty function has been added to make it easier to
    create frames on new terminals.

*** New functions: frame-tty-name, frame-tty-type, delete-tty,
    terminal-local-value, set-terminal-local-value

    terminal-id, terminal-parameters, terminal-parameter,
    set-terminal-parameter

*** New variables: global-key-translation-map

*** The keymaps key-translation-map and function-key-map are now
    terminal-local.

** Support for simultaneous graphical and terminal frames has been
   added.

*** The function `make-frame-on-display' now works during a terminal
    session, and `make-frame-on-tty' works during a graphical session.

*** The `window-system' variable has been made frame-local.

*** The new `initial-window-system' variable contains the
    `window-system' value for the first frame.

*** talk.el has been extended for multiple tty support.


* * *

(The rest of this file consists of my development notes and as such it
is probably not very interesting for anyone else.)

THINGS TO DO
------------

** Report GTK multi-display problems to GTK maintainers.  For extra
   credit, fix them.

** 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.

** 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.

** 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.

** Add the following hooks: after-delete-frame-hook (for server.el,
   instead of delete-frame-functions),
   after-delete-terminal-functions, after-create-terminal-functions.

** 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.

** 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)?

** 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
   can be renamed without aliases:

    display-controlling-tty-p           terminal-controlling-tty-p
    display-list                        terminal-list
    display-live-p                      terminal-live-p
    display-name                        terminal-name
    display-tty-type                    terminal-tty-type
    frame-display                       terminal-of-frame
    delete-display                      delete-terminal

** 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'.

** I think keyboard-translate-table should be made terminal-local.

** 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.

** 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-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.)

** Dan Nicolaescu suggests that -nw should be added as an alias for -t
   in emacsclient.  Good idea.  (Alas, implementing this is not
   trivial, getopt_long does not seem to support two-letter ``short''
   options.  Patches are welcome.) :-)

** Mark Plaksin suggests that emacsclient should accept the same
   X-related command-line arguments as Emacs.  Most of the X-related
   argument-handling is done in Lisp, so this should be quite easy to
   implement.

** 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 noticable.

** 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.)

** Fix Mac support (I can't do this entirely myself).  Note that the
   current state of Mac-specific source files in the multi-tty tree
   are not useful; before starting work on Mac support, revert to
   pristine, pre-multi-tty versions.

** Fix W32 support (I can't do this entirely myself).  Note that the
   current state of W32-specific source files in the multi-tty tree
   are not useful; before starting work on W32 support, revert to
   pristine, pre-multi-tty versions.

** Fix DOS support (I can't do this entirely myself).  Note that the
   current state of DOS-specific source files in the multi-tty tree
   are not useful; before starting work on DOS support, revert to
   pristine, pre-multi-tty versions.

** Do a grep on XXX and ?? for more issues.

** 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.)

** 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 modifiying 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 behaviour 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 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, broking 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.  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 initialialized 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.)

-- Miles Bader suggests that C-x C-c on an emacsclient frame should
   only close the frame, not exit the entire Emacs session.  Update:
   see above for a function that does this.  Maybe this should be the
   new default?  

   (Done.  This is the new default.  No complaints so far.)

-- Clean up the frame-local variable system.  I think it's ugly and
   error-prone.  But maybe I just haven't yet fully understood it.

   (Nothing to do.  It doesn't seem ugly any more.  It's rather clever.)

-- 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.)

-- Make `function-key-map' and `key-translation-map' terminal-local.

   (Done.)

-- Implement `terminal-local-value' and `set-terminal-local-value' to
   allow deterministic access to terminal local bindings.  The
   encode-kb package can not set up `key-translation-map' without
   these.  The terminal-local bindings seem to be independent of what
   frame is selected.

   (Done.)

-- 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.)

;;; arch-tag: 8da1619e-2e79-41a8-9ac9-a0485daad17d