5 The ultimate goal of this branch is to implement support for opening
6 multiple, different tty devices and simultaneous X and tty frames from
7 a single Emacs session.
11 Emacs is notoriously slow at startup, so most people use another
12 editor or emacsclient for quick editing jobs from the console.
13 Unfortunately, emacsclient was very awkward to use, because it did not
14 support opening a new Emacs frame on the current virtual console.
15 Now, with multi-tty support, it can do that. (Emacsclient starts up
18 Some Gnus users (including me) run Gnus in an X frame in its own Emacs
19 instance, which they typically leave running for weeks. It would be
20 nice if they could connect to this instance from a remote ssh session
21 and check their messages without opening a remote X frame or resorting
28 I'm Károly Lőrentey. My address: lorentey@elte.hu.
30 Patches or suggestions are welcome!
32 Retrieving the latest version of the branch:
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>
37 (I use a recent arch development snapshot, but any of the released
38 versions of arch will do fine, I think.)
40 If you don't have arch, the branch has a homepage from which you can
41 download conventional patches against Emacs CVS HEAD:
43 http://lorentey.web.elte.hu/project/emacs.html
48 Multi-tty support is stable, I think most of the problems were fixed.
49 (It still needs testing on other architectures, though.) Please let
50 me know if you find any bugs in it. Emacsclient has been extended to
51 support opening a new terminal frame.
53 To try it out, compile and run the multi-tty branch with the following
63 and then (from a shell prompt on another terminal) start emacsclient
66 lib-src/emacsclient -t /optional/file/names...
68 You'll hopefully have two fully working, independent frames on
69 separate terminals. The new frame is closed automatically when you
70 have finished editing the specified files (C-x #), but delete-frame
71 (C-x 5 0) also works. Of course, you can create frames on more than
74 Creating new frames on the same tty with C-x 5 2 works, and they
75 behave the same way as in previous Emacs versions. If you exit emacs,
76 all terminals should be restored to their previous states.
78 This is work in progress, and probably full of bugs. You should
79 always run emacs from gdb, so that you'll have a live instance to
80 debug if something goes wrong. Please send me your reports.
84 * Suspending Emacs is disabled if there are multiple tty
85 devices. Also, there is no way to suspend emacsclient. This
88 * X support is (I hope) working, but at the moment there are
89 problems with simultaneous X and tty devices, so don't do
90 that - start a separate Emacs with -nw and run the server
93 * Mac, Windows and DOS support is broken, probably doesn't
94 even compile -- this will be solved later.
96 * Only tested on my GNU/Linux box.
103 ** Support for multiple terminal devices has been added. You can
104 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
107 be problems with terminal input and window resizes.
109 You can test for the presence of multiple terminal support by
110 testing for the `multi-tty' feature.
112 ** A make-frame-on-tty function has been added to make it easier to
113 create frames on new terminals.
115 ** New functions: frame-tty-name, frame-tty-type for accessing
116 terminal parameters, and delete-tty for closing the terminal
119 ** Emacsclient has been extended to support opening a new terminal
130 ** Fix rif issue with X-tty combo sessions. IMHO the best thing to do
131 is to get rid of that global variable (and use the value value in
132 display_method, which is guaranteed to be correct).
134 ** Fix faces on tty frames during X-tty combo sessions.
136 ** During an X-tty combo session, a (message "Hello") from a tty frame
137 goes to the X frame. Fix this.
139 ** Find out the best way to support suspending Emacs with multiple
140 ttys. My guess: disable it on the controlling tty, but from other
141 ttys pass it on to emacsclient somehow. (It is (I hope) trivial to
142 extend emacsclient to handle suspend/resume. A `kill -STOP' almost
145 ** Move baud_rate to tty_output.
147 ** Do tty output through term_hooks, like graphical display backends.
149 ** Implement support for starting an interactive Emacs session without
150 an initial frame. (The user would connect to it and open frames
151 later, with emacsclient.) Not necessarily a good idea.
153 ** Fix input from raw ttys (again).
155 ** Fix Mac support (I can't do this myself).
157 ** Fix W32 support (I can't do this myself).
159 ** Fix DOS support (I can't do this myself).
161 ** Do a grep on XXX and ?? for more issues.
163 ** Understand Emacs's low-level input system (it seems complicated) :-)
165 ** What does interrupt_input do? I tried to disable it for raw
166 secondary tty support, but it does not seem to do anything useful.
167 (Update: Look again. X unconditionally enables this, maybe that's
168 why raw terminal support is broken again. I really do need to
171 ** Make sure C-g goes to the right frame. This is hard, as SIGINT
172 doesn't have a tty parameter. :-(
174 ** I have seen a case when Emacs with multiple ttys fell into a loop
175 eating 100% of CPU time. Strace showed this loop:
178 kill(30284, SIGIO) = 0
179 --- SIGIO (I/O possible) @ 0 (0) ---
180 ioctl(6, FIONREAD, [0]) = -1 EIO (Input/output error)
181 ioctl(5, FIONREAD, [0]) = -1 EIO (Input/output error)
182 ioctl(0, FIONREAD, [0]) = 0
183 sigreturn() = ? (mask now [])
184 gettimeofday({1072842297, 747760}, NULL) = 0
185 gettimeofday({1072842297, 747806}, NULL) = 0
186 select(9, [0 3 5 6], NULL, NULL, {0, 0}) = 2 (in [5 6], left {0, 0})
187 select(9, [0 3 5 6], NULL, NULL, {0, 0}) = 2 (in [5 6], left {0, 0})
188 gettimeofday({1072842297, 748245}, NULL) = 0
190 I have not been able to reproduce this.
192 ** Define a output_initial value for output_method for the initial
193 frame that is dumped with Emacs. Checking for this frame (e.g. in
194 cmd_error_internal) is ugly.
196 ** emacsclient -t from an Emacs term buffer does not work, complains
197 about face problems. This can even lock up Emacs (if the recursive
198 frame sets single_kboard).
203 (ex-TODO items with explanations.)
205 -- Introduce a new struct for terminal devices.
207 (Done, see struct tty_output. The list of members is not yet
210 -- Change the bootstrap procedure to initialize tty_list.
212 (Done, but needs review.)
214 -- Change make-terminal-frame to support specifying another tty.
216 (Done, new frame parameters: `tty' and `tty-type'.)
218 -- Implement support for reading from multiple terminals.
220 (Done, read_avail_input tries to read from each terminal, until one
221 succeeds. MULTI_KBOARD is not used. Secondary terminals don't send
224 (Update: They do, now.)
226 (Update2: After enabling X, they don't.)
228 -- other-frame should cycle through the frames on the `current'
231 (Done, by trivially modifiying next_frame and prev_frame.)
233 -- Support different terminal sizes.
237 -- Make sure terminal resizes are handled gracefully. (Could be
240 (Done. We don't get automatic SIGWINCH for additional ttys,
243 -- Extend emacsclient to automatically open a new tty when it connects
246 (Done. It's an ugly hack, needs more work.)
248 -- Redisplay must refresh the topmost frame on *all* terminals, not
249 just the initial terminal.
251 (Done, but introduced an ugly redisplay problems. Ugh.)
253 -- Fix redisplay problems.
255 (Done; it turned out that the entire Wcm structure must be moved
256 inside tty_output. Why didn't I catch this earlier?)
258 -- Provide a way for emacsclient to tell Emacs that the tty has been
261 (Done, simply forward the SIGWINCH signal.)
263 -- Each keypress should automatically select the frame corresponding
264 to the terminal that it was coming from. This means that Emacs
265 must know from which terminal the last keyboard event came from.
267 (Done, it was quite simple, the input event system already
268 supported multiple frames.)
270 -- Fix SIGIO issue with secondary terminals.
272 (Done, emacsclient signals Emacs after writing to the proxy pseudo
273 terminal. Note that this means that multi-tty does not work with
276 (Update: This is bullshit. There is a read_input_waiting function,
277 extend that somehow.)
279 (Update of update: The first update was not right either, extending
280 read_input_waiting was not necessary. Secondary ttys do seem to
281 send signals on input.)
283 (Update^3: Not any more.)
285 -- Make make-terminal-frame look up the `tty' and `tty-type' frame
286 parameters from the currently selected terminal before the global
291 -- Put all cached terminal escape sequences into struct tty_output.
292 Currently, they are still stored in global variables, so we don't
293 really support multiple terminal types.
295 (Done. It was not fun.)
297 -- Implement sane error handling after initialization. (Currently
298 emacs exits if you specify a bad terminal type.) The helpful error
299 messages must still be provided when Emacs starts.
303 -- Implement terminal deletion, i.e., deleting local frames, closing
304 the tty device and restoring its previous state without exiting
307 (Done, but at the moment only called when an error happens during
308 initialization. There is a memory corruption error around this
309 somewhere.) (Update: now it is fully enabled.)
311 -- Implement automatic deletion of terminals when the last frame on
312 that terminal is closed.
316 -- Restore tty screen after closing the terminal.
318 (Done, we do the same as Emacs 21.2 for all terminals.)
320 -- 'TERM=dumb src/emacs' does not restore the terminal state.
324 -- C-g should work on secondary terminals.
326 (Done, but the binding is not configurable.)
328 -- Deal with SIGHUP in Emacs and in emacsclient. (After this, the
329 server-frames may be removed from server.el.)
331 (Done, nothing to do. It seems that Emacs does not receive SIGHUP
332 from secondary ttys, which is actually a good thing.) (Update: I
333 think it would be a bad idea to remove server-frames.)
335 -- Change emacsclient/server.el to support the -t argument better,
336 i.e. automatically close the socket when the frame is closed.
338 (Seems to be working OK.)
340 -- Fix mysterious memory corruption error with tty deletion. To
341 trigger it, try the following shell command:
343 while true; do TERM=no-such-terminal-definition emacsclient -h; done
345 Emacs usually dumps core after a few dozen iterations. (The bug
346 seems to be related to the xfree()ing or bzero()ing of
347 tty_output.Wcm. Maybe there are outside references to struct Wcm?
348 Why were these vars collected into a struct before multi-tty
351 (Done. Whew. It turned out that the problem had nothing to do
352 with hypothetical external references to Wcm, or any other
353 tty_output component; it was simply that delete_tty closed the
354 filehandles of secondary ttys twice, resulting in fclose doubly
355 free()ing memory. Utterly trivial matter. I love the C's memory
356 management, it puts hair on your chest.)
358 -- Support raw secondary terminals. (Note that SIGIO works only on
359 the controlling terminal.) Hint: extend read_input_waiting() for
360 multiple ttys and hopefully this will be fixed.
362 (Done, it seems to have been working already for some time. It
363 seems F_SETOWN does work, after all. Not sure what made it fail
364 earlier, but it seems to be fixed (there were several changes
365 around request_sigio, maybe one of them did it).
366 read_input_waiting() is only used in sys_select(), don't change
367 it.) (Update: After adding X support, it's broken again.)
369 -- Find out why does Emacs abort when it wants to close its
370 controlling tty. Hint: chan_process[] array. Hey, maybe
371 noninterrupt-IO would work, too? Update: no, there is no process
374 (Done. Added add/delete_keyboard_wait_descriptor to
375 term_init/delete_tty. The hint was right, in a way.)
377 -- Issue with SIGIO: it needs to be disabled during redisplay. See if
378 fcntl() kernel behaviour could be emulated by emacsclient.
380 (Done. Simply disabled the SIGIO emulation hack in emacsclient.)
381 (Update: it was added back.)
383 -- server.el: There are issues with saving files in buffers of closed
384 clients. Try editing a file with emacsclient -f, and (without
385 saving it) do a delete-frame. The frame is closed without
386 question, and a surprising confirmation prompt appears in another
389 (Done. delete-frame now asks for confirmation if it still has
390 pending buffers, and modified buffers don't seem to be deleted.)
392 -- emacsclient.el, server.el: Handle eval or file open errors when
397 -- Make parts of struct tty_output accessible from Lisp. The device
398 name and the type is sufficient.
400 (Done, see frame-tty-name and frame-tty-type.)
402 -- Export delete_tty to the Lisp environment, for emacsclient.
404 (Done, see delete-tty.)
406 -- Get rid of the accessor macros in termchar.h, or define macros for
411 -- Move device-specific parameters (like costs) commonly used by
412 device backends to a common, device-dependent structure.
414 (Done. See struct display_method in termhooks.h.)
418 (Done. Well, it seems to be working.)
420 -- Allow simultaneous X and tty frames. (Handling input could be
421 tricky. Or maybe not.)
423 (Done. Allowed, that is. It is currently extremely unstable, to
424 the point of being unusable. The rif variable causes constant
425 core dumps. Handling input is indeed tricky.)
427 -- Rewrite multi-tty input in terms of MULTI_KBOARD.
429 (Done. In fact, there was no need to rewrite anything, I just
430 added a kboard member to tty_display_info, and initialized the
431 frame's kboard from there.)
433 ;;; arch-tag: 8da1619e-2e79-41a8-9ac9-a0485daad17d