README.multi-tty 16.3 KB
Newer Older
1 2 3 4 5 6 7 8
			-*- 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.

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
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.


25 26 27 28 29 30 31
WHO IS DOING IT
---------------

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

Patches or suggestions are welcome!

32
Retrieving the latest version of the branch:
33 34

	tla register-archive lorentey@elte.hu--2004 http://lorentey.web.elte.hu/arch/2004/
35
	tla get lorentey@elte.hu--2004/emacs--multi-tty <directory>
36

37 38 39 40 41
(I use a recent arch development snapshot, but any of the released
versions of arch will do fine, I think.)

If you don't have arch, the branch has a homepage from which you can
download conventional patches against Emacs CVS HEAD:
42

43
	http://lorentey.web.elte.hu/project/emacs.html
44 45 46 47

STATUS
------

48 49 50 51
Multi-tty support is stable, I think most of the problems were fixed.
(It still needs testing on other architectures, though.)  Please let
me know if you find any bugs in it.  Emacsclient has been extended to
support opening a new terminal frame.
52

53
To try it out, compile and run the multi-tty branch with the following
Karoly Lorentey's avatar
Karoly Lorentey committed
54
commands:
55 56 57

   	mkdir +build
	cd +build
58
	../configure
59
	make bootstrap
60 61
	src/emacs -nw
	M-x server-start
62

63 64
and then (from a shell prompt on another terminal) start emacsclient
with
65

66
	lib-src/emacsclient -t /optional/file/names...
67

Karoly Lorentey's avatar
Karoly Lorentey committed
68
You'll hopefully have two fully working, independent frames on
69 70 71 72
separate terminals. The new frame is closed automatically when you
have finished 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.
73

74 75 76
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.
77

78 79 80
This is work in progress, and probably full of bugs.  You should
always run emacs from gdb, so that you'll have a live instance to
debug if something goes wrong.  Please send me your reports.
Karoly Lorentey's avatar
Karoly Lorentey committed
81

82
Problems:
83

84 85 86 87 88 89 90 91 92 93 94 95 96
	* Suspending Emacs is disabled if there are multiple tty
	  devices.  Also, there is no way to suspend emacsclient. This
	  will be fixed.

	* X support is (I hope) working, but at the moment there are
	  problems with simultaneous X and tty devices, so don't do
	  that - start a separate Emacs with -nw and run the server
	  there.

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

	* Only tested on my GNU/Linux box.
97 98 99 100 101 102 103 104

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
105
   (`tty-type' parameter) to `make-terminal-frame'. `tty' must be a
106
   terminal device created by the updated emacsclient, or there will
Karoly Lorentey's avatar
Karoly Lorentey committed
107
   be problems with terminal input and window resizes.  
108 109 110 111 112 113

   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.
114

115 116 117 118
** New functions: frame-tty-name, frame-tty-type for accessing
   terminal parameters, and delete-tty for closing the terminal
   device.

119 120
** Emacsclient has been extended to support opening a new terminal
   frame.
121 122 123 124 125 126

CHANGELOG
---------

See arch logs.

127 128 129
THINGS TO DO
------------

130 131 132 133 134
** Fix color handling during X+tty 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 done in lisp (term/tty-colors.el).)
135

136
** The command `emacsclient -t -e '(delete-frame)'' fails to exit.
137 138 139 140 141 142 143

** 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.)

144 145 146
** During an X session, Emacs seems to read from stdin.

** Move baud_rate to struct display.
147

148 149
** Do tty output through struct display, like graphical display
   backends.
150 151 152 153 154 155 156 157 158 159 160 161 162 163

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

** 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).

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

** Understand Emacs's low-level input system (it seems complicated) :-)
164
   What does interrupt_input do?  I tried to disable it for raw
165 166 167 168 169
   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.)

170 171
** Make sure C-g goes to the right frame with ttys.  This is hard, as
   SIGINT doesn't have a tty parameter. :-(
172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188

** 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

189 190
   I have seen something similar with a single X frame, but have not
   been able to reproduce it for debugging.
191

192 193 194 195 196
   Update: This may have been caused by checking for nread != 0
   instead of nread > 0 after calling read_socket_hook in
   read_avail_input.

** Define an output_initial value for output_method for the initial
197 198 199 200 201
   frame that is dumped with Emacs.  Checking for this frame (e.g. in
   cmd_error_internal) is ugly.

** emacsclient -t from an Emacs term buffer does not work, complains
   about face problems.  This can even lock up Emacs (if the recursive
202 203 204
   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.
205

206 207 208 209
DIARY OF CHANGES
----------------

(ex-TODO items with explanations.)
210

211
-- Introduce a new struct for terminal devices.  
212

213
   (Done, see struct tty_output.  The list of members is not yet
214 215 216 217 218 219 220 221 222 223
   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'.)

224 225 226
-- Implement support for reading from multiple terminals.

   (Done, read_avail_input tries to read from each terminal, until one
227
   succeeds.  MULTI_KBOARD is not used.  Secondary terminals don't send
228
   SIGIO!)
229

230 231
   (Update: They do, now.)

232 233
   (Update2: After enabling X, they don't.)

234
-- other-frame should cycle through the frames on the `current'
235
   terminal only.  
236

237
   (Done, by trivially modifiying next_frame and prev_frame.)
238 239 240 241 242 243 244 245

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

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

246 247
   (Done.  We don't get automatic SIGWINCH for additional ttys,
   though.)
248 249 250 251 252 253

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

254 255
-- Redisplay must refresh the topmost frame on *all* terminals, not
   just the initial terminal.
256
   
257
   (Done, but introduced an ugly redisplay problems.  Ugh.)
258

259 260
-- Fix redisplay problems.

261 262
   (Done; it turned out that the entire Wcm structure must be moved
   inside tty_output.  Why didn't I catch this earlier?)
263 264 265 266 267 268 269 270 271 272

-- 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.

273 274
   (Done, it was quite simple, the input event system already
   supported multiple frames.)
275 276 277 278

-- Fix SIGIO issue with secondary terminals.

   (Done, emacsclient signals Emacs after writing to the proxy pseudo
279 280
   terminal.  Note that this means that multi-tty does not work with
   raw ttys!)
281

Karoly Lorentey's avatar
Karoly Lorentey committed
282 283 284
   (Update: This is bullshit.  There is a read_input_waiting function,
   extend that somehow.)

285 286 287 288
   (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.)

289 290
   (Update^3: Not any more.)

291 292 293 294 295 296 297 298 299 300
-- 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.

301
   (Done.  It was not fun.)
302 303

-- Implement sane error handling after initialization.  (Currently
304 305 306
   emacs exits if you specify a bad terminal type.)  The helpful error
   messages must still be provided when Emacs starts.

307 308 309 310 311
   (Done.)

-- Implement terminal deletion, i.e., deleting local frames, closing
   the tty device and restoring its previous state without exiting
   Emacs.
312

313 314
   (Done, but at the moment only called when an error happens during
   initialization.  There is a memory corruption error around this
315
   somewhere.)  (Update: now it is fully enabled.)
316

317 318 319 320 321
-- Implement automatic deletion of terminals when the last frame on
   that terminal is closed.

   (Done.)

Karoly Lorentey's avatar
Karoly Lorentey committed
322 323 324 325 326 327 328
-- 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.)
329

330 331 332 333 334 335 336 337
-- 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
338
   from secondary ttys, which is actually a good thing.)  (Update: I
339
   think it would be a bad idea to remove server-frames.)
340

341
-- Change emacsclient/server.el to support the -t argument better,
342 343 344 345
   i.e. automatically close the socket when the frame is closed.

   (Seems to be working OK.)

346
-- Fix mysterious memory corruption error with tty deletion.  To
347 348 349 350 351 352
   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
353 354 355
   tty_output.Wcm.  Maybe there are outside references to struct Wcm?
   Why were these vars collected into a struct before multi-tty
   support?)
356

357 358 359 360 361 362 363
   (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
   free()ing memory.  Utterly trivial matter.  I love the C's memory
   management, it puts hair on your chest.)

364 365 366
-- 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.
367

368 369 370 371 372
   (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
373
   it.)  (Update: After adding X support, it's broken again.)
374

375
-- Find out why does Emacs abort when it wants to close its
Karoly Lorentey's avatar
Karoly Lorentey committed
376
   controlling tty.  Hint: chan_process[] array.  Hey, maybe
377 378
   noninterrupt-IO would work, too?  Update: no, there is no process
   for stdin/out.
Karoly Lorentey's avatar
Karoly Lorentey committed
379

380 381
   (Done.  Added add/delete_keyboard_wait_descriptor to
   term_init/delete_tty.  The hint was right, in a way.)
382

383
-- Issue with SIGIO: it needs to be disabled during redisplay.  See if
Karoly Lorentey's avatar
Karoly Lorentey committed
384 385
   fcntl() kernel behaviour could be emulated by emacsclient.

386
   (Done.  Simply disabled the SIGIO emulation hack in emacsclient.)
387
   (Update: it was added back.)
388

389
-- server.el: There are issues with saving files in buffers of closed
390 391 392 393 394
   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.

395 396 397 398
   (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
399
   doing -t.
400

401
   (Done.)
402

403 404
-- Make parts of struct tty_output accessible from Lisp.  The device
   name and the type is sufficient.
405

406 407 408
   (Done, see frame-tty-name and frame-tty-type.)

-- Export delete_tty to the Lisp environment, for emacsclient.
409

410 411
   (Done, see delete-tty.)

412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431
-- 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.)
432

433
-- Rewrite multi-tty input in terms of MULTI_KBOARD.
434

435 436 437
   (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.)
438

439 440 441 442 443 444 445
-- 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.)

446 447 448 449
-- Add multi-tty support to talk.el.

   (Done.)

450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483
-- 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.)

484
;;; arch-tag: 8da1619e-2e79-41a8-9ac9-a0485daad17d