README.multi-tty 7.59 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
			-*- coding: utf-8; -*-
GOAL
----

The ultimate goal of this branch is to implement support for opening
multiple, different tty devices and simultaneous X and tty frames from
a single Emacs session.

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

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

Patches or suggestions are welcome!

16
Retrieving the latest version of the branch:
17 18 19 20 21 22

	tla register-archive lorentey@elte.hu--2004 http://lorentey.web.elte.hu/arch/2004/
	tla get lorentey@elte.hu--2004/emacs--multi-tty--0 <directory>

(I use tla 1.1.)

23 24 25 26

STATUS
------

27 28 29
Basic multi-tty support is there; there are some rough edges, but it
already seems to be usable.  Emacsclient has been extended to support
opening a new terminal frame.
30

31 32 33 34 35 36 37 38
To try it out, compile Emacs with the following commands

   	mkdir +build
	cd +build
	../configure --with-x-toolkit=no --without-x
	make bootstrap

then start up the emacs server (src/emacs, M-x server-start), and then
39
(from a shell prompt on another terminal) start emacsclient with
40

41
	lib-src/emacsclient -h
42

43 44
You'll hopefully have two fully working frames on separate terminals.
If you exit emacs, both terminals should be restored to their previous
Karoly Lorentey's avatar
Karoly Lorentey committed
45
states.  You can close the newly opened frame and return to the shell
46
without exiting Emacs by pressing C-x 5 0, i.e., delete-frame.
47 48 49

X, Mac, Windows and DOS support is broken, probably doesn't even
compile -- this will be solved later.
50 51

Tested under GNU/Linux only.
52 53 54 55 56 57 58 59

NEWS
----

For the NEWS file:

** Support for multiple terminal devices has been added.  You can
   specify a terminal device (`tty' parameter) and a terminal type
60
   (`tty-type' parameter) to `make-terminal-frame'. `tty' must be a
61 62
   terminal device created by the updated emacsclient, or there will
   be problems with terminal input and window resizes.  (The kernel
63 64 65 66 67 68 69 70 71 72
   notifies processes about pending input or terminal resizes only on
   the controlling terminal, so we need emacsclient to sit on the real
   terminal device, create SIGIO signals upon terminal input, and
   forward SIGWINCH signals to us.)

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

** A make-frame-on-tty function has been added to make it easier to
   create frames on new terminals.
73

74 75
** Emacsclient has been extended to support opening a new terminal
   frame.
76 77 78 79 80 81 82

CHANGELOG
---------

See arch logs.


83 84 85 86
DIARY OF CHANGES
----------------

(ex-TODO items with explanations.)
87 88 89 90 91 92 93 94 95 96 97 98 99 100

-- Introduce a new abstraction for terminal devices.  

   (Done, see struct tty_output.  The abstraction 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'.)

101 102 103
-- Implement support for reading from multiple terminals.

   (Done, read_avail_input tries to read from each terminal, until one
104 105
   succeeds.  MULTIKBOARD is not used.  Secondary terminals don't send
   SIGIO!)
106 107

-- other-frame should cycle through the frames on the `current'
108
   terminal only.  
109

110
   (Done, by trivially modifiying next_frame and prev_frame.)
111 112 113 114 115 116 117 118

-- Support different terminal sizes.
   
   (Done, no problem.)

-- Make sure terminal resizes are handled gracefully.  (Could be
   problematic.)

119 120
   (Done.  We don't get automatic SIGWINCH for additional ttys,
   though.)
121 122 123 124 125 126

-- Extend emacsclient to automatically open a new tty when it connects
   to Emacs.
   
   (Done.  It's an ugly hack, needs more work.)

127 128
-- Redisplay must refresh the topmost frame on *all* terminals, not
   just the initial terminal.
129
   
130
   (Done, but introduced an ugly redisplay problems.  Ugh.)
131

132 133
-- Fix redisplay problems.

134 135
   (Done; it turned out that the entire Wcm structure must be moved
   inside tty_output.  Why didn't I catch this earlier?)
136 137 138 139 140 141 142 143 144 145

-- 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.

146 147
   (Done, it was quite simple, the input event system already
   supported multiple frames.)
148 149 150 151

-- Fix SIGIO issue with secondary terminals.

   (Done, emacsclient signals Emacs after writing to the proxy pseudo
152 153
   terminal.  Note that this means that multi-tty does not work with
   raw ttys!)
154

155 156 157 158 159 160 161 162 163 164
-- 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.

165
   (Done.  It was not fun.)
166 167

-- Implement sane error handling after initialization.  (Currently
168 169 170
   emacs exits if you specify a bad terminal type.)  The helpful error
   messages must still be provided when Emacs starts.

171 172 173 174 175
   (Done.)

-- Implement terminal deletion, i.e., deleting local frames, closing
   the tty device and restoring its previous state without exiting
   Emacs.
176

177 178 179 180
   (Done, but at the moment only called when an error happens during
   initialization.  There is a memory corruption error around this
   somewhere.)

181 182 183 184 185
-- Implement automatic deletion of terminals when the last frame on
   that terminal is closed.

   (Done.)

186 187 188 189 190 191 192 193 194 195 196

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

** 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 xfree()ing or bzero()ing of
197 198 199
   tty_output.Wcm or some other tty_output part.  Maybe there are
   outside references to struct Wcm?  Why were these vars collected
   into a struct before multi-tty support?)
200

201
   The bug does not seem to happen if the error occurs before terminal
202
   initialization or if I comment out all xfree()s in delete_frame.
203 204
   Update: yes it does, although it is much rarer.  Or maybe it's
   another bug.
205

206 207
** Change emacsclient/server.el to support the -h argument better,
   i.e. automatically close the socket when the frame is closed.
208

209 210
** Export delete_tty to the Lisp environment, for emacsclient.

Karoly Lorentey's avatar
Karoly Lorentey committed
211 212 213 214
** Restore tty screen after closing the terminal.

** 'TERM=dumb src/emacs' does not restore the terminal state.

215
** C-g should work on secondary terminals.
216

217 218
** Make parts of struct tty_output accessible from Lisp.  The device
   name and the type is sufficient.
219

Karoly Lorentey's avatar
Karoly Lorentey committed
220 221 222
** Find out why does Emacs abort when it wants to close its
   controlling tty.

223 224
** Implement support for starting an interactive Emacs session without
   an initial frame.  (The user would connect to it and open frames
225
   later, with emacsclient.)  Not necessarily a good idea.
226

227
** Support raw secondary terminals.  (This one is tricky, SIGIO works
228 229
   only on the controlling terminal.  The emacsclient solution works
   nicely, so this is not that important anyway.)
230 231

** What does interrupt_input do?  I tried to disable it for raw
232
   secondary tty support, but it does not seem to do anything useful.
233

234 235
** Move optimalization parameters (costs) from union output_data to
   a backend-neutral per-device structure.
236

Karoly Lorentey's avatar
Karoly Lorentey committed
237 238 239 240
** Find out the best way to support suspending Emacs with multiple
   ttys.

** Do tty output through term_hooks, like all other display backends.
241

242 243
** Fix X support.

244 245 246 247 248 249 250 251 252 253 254
** Allow simultaneous X and tty frames.

** Fix Mac support (I can't do this myself).

** Fix W32 support (I can't do this myself).

** Fix DOS support (I can't do this myself).



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