Dave Lawrence (01/06/89)
Okay, thanks to all the information I got I tracked down a GNU Elisp
manual and was pretty content with how much smoother some things got
from there. Now I am having a couple of problems with a filter I am
writing for an asynchronous process. I'll work my way from smallest
description to largest description.
First off, what does waiting-for-user-input-p do? I have a feeling
that it could be very helpful to me as it is described in the manual
as being for asynch processes, yet there isn't much more than that.
I can't get it to ever return anything other than t, so having it
seems a little stupid to me. I am certain I am missing the boat on it
though.
Secondly, and I was hoping that the affore-mentioned predicate would
help me here, is that if I am in the minibuffer when output from the
process arrives then the next character typed ends up in the buffer
rather than the minibuffer. I can't explain it, but I'll be my code
can. :-)
Third, I am trying to emulate tty scrolling. I am not trying to do
anything else as far as terminal emulation goes. Please don't make
the suggestion that I should look at terminal.el because that code is
no help and I do not want my job running under terminal emulator, I
only want the scrolling. That code is pretty messy (although humorous
in spots) and when I searched through it for every occurence of
`terminal-scrolling' and it turns out that the "magic" done by it is
in the TERMCAP. The two problems that I am finding is this: (a)
scroll-step works in a very peculiar manner and (b) sometimes Emacs
decides to just scroll up from the bottom and other times it decides
to redraw the screen from the top (with the net result of moving the
screen up one line). What controls the latter behaviour?
More on problem (a): I tried to overcome the problem in a number of
ways. First, I would set `scroll-step' (local to the buffer of
course) equal to the number of LFDs in the string before I inserted
the string and then reset it to 1 after I had gone to (point-max).
The problem with this was that it ALWAYS exhibited the behaviour of
having scroll-step set to 1. I did a number of tests to make sure
that my count-lfd function was working properly and that scroll-step
was indeed being set. They were positive. So I said to myself
"forget resetting scroll-step to 1". Things worked a little bit
better but not entirely; I still wanted scroll-step to be 1 for the
purposes of user input. I tried setting scroll-step to 1+ the number
of LFDs. I tried changing all sorts of locations in the filter where
I set/reset scroll-step. I tried adding sleep|sit-fors and that just
made things horribly worse. The way things are now, scroll-step is
perpetually set to 1 and I send things line-at-a-time. Why this
doesn't work is also a mystery to me. So how can I get terminal
scrolling?
What follows is the filter. I'm sorry if it's not good form or
something, but (e)lisp is still new to me; in fact, I'd appreciate any
(constructive) criticism that anyone would want to give.
The process:
telnet is run with an explicit hostname and port to connect to an
asynchronous communication programme.
Stuff in the filter:
(truncate-buffer buffer size) is just a quick and dirty routine that
makes sure the buffer size stays below an certain limit. Sessions in
this programme can potentially run for days and millions of
characters, so a ceiling is needed.
(count-lfd string) returns the number of linefeed chars in string.
(handle-password) sends the entered password to the process. It does
password blanking which I am frankly surprised that telnet and ftp
don't do.
last-output-end is a marker for me to distinguish the input-region
from the output-region (as defined by me). This is important for the
purposes of my self-inserting characters and delete, among other
things. (process-mark) won't do because I need different information.
dist-from-output-end simply lets me retain whereever I was in relation
to last-output-end.
Finally, here is the code. Many many thanks in advance for any help
that might be provided. It will be greatly appreciated.
(defun connect-initial-filter (proc string)
"Fitlers everything up to the `Enter connect ...' prompt."
(cond
((string-match "^Welcome to" string) ; turn off echoing
(send-string proc "\n")
(connect-filter proc string))
((string-match "" string) ; don't let the ^E back
(connect-filter proc
(concat (substring string 0 (match-beginning 0))
(substring string (match-end 0) nil))))
((string-match "^Enter" string)
(connect-filter proc string)
(set-process-filter proc 'connect-filter))
((string-match "^teln" string) ; oops. telnet didn't make it
(kill-buffer (process-buffer proc))
(error "Telnet couldn't connect to Network Server"))
(t (connect-filter proc string))))
(defun connect-filter (proc string)
"Filtering procedure for ACM Network Server."
(set-buffer (process-buffer proc))
(truncate-buffer (process-buffer proc) connect-maximum-size)
(let ((dist-from-output-end (- (point) last-output-end)) substr-lfd)
(save-excursion
(goto-char last-output-end)
(let ((now (point)))
(insert (substring string 0 ; send one line only
(cond ((setq substr-lfd (string-match "\n" string))
(setq substr-lfd (1+ substr-lfd))))))
(cond ((string-match "^password: " string)
(handle-password)))
(setq last-output-end (point))
(let ((now-end (point)))
(while (search-backward "
(delete-char 1)
(setq last-output-end (1- last-output-end)))
(goto-char now-end)
(while (search-backward "" now t) (ding)
(message "Bell in *Connect*")
(delete-char 1)
(setq last-output-end (1- last-output-end))))))
(if (and (eq (process-buffer proc) (current-buffer))
(> dist-from-output-end -1))
(goto-char (+ last-output-end dist-from-output-end)))
(if (and substr-lfd (> (length string) substr-lfd))
(connect-filter proc (substring string substr-lfd nil)))))
(I never get more than 5 LFDs at a time, so recursion is okay.)
Thanks again and sorry this was so long.
Dave
--
tale@rpitsmts.bitnet, tale%mts@rpitsgw.rpi.edu, tale@pawl.rpi.edu