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From: glenn@nsc.UUCP (Glenn Skinner)
Newsgroups: net.emacs
Subject: Re: a simple problem for 4.2 gosling-emacs
Message-ID: <2685@nsc.UUCP>
Date: Thu, 9-May-85 12:51:12 EDT
Article-I.D.: nsc.2685
Posted: Thu May  9 12:51:12 1985
Date-Received: Sat, 11-May-85 01:42:52 EDT
References: <271@sbcs.UUCP>
Reply-To: glenn@nsc.UUCP (Glenn Skinner)
Distribution: net
Organization: National Semiconductor, Sunnyvale
Lines: 55
Summary: keymaps to the rescue!

In article <271@sbcs.UUCP> podar@sbcs.UUCP (Sunil Podar) wanted to write
an MLisp function that used command completion to get a buffer name, but
that supplied a default buffer name if the user simply typed CR as a response.

The following function can be used to construct such a function.  He suggested
that someone send him a solution by mail, but since the technique used is
nonobvious, I decided to post the solution.  The basic idea is to use a local
keymap that binds everything to self-insert-and-exit to obtain a single
character.  If this character is CR, we return the default buffer name.
Otherwise, we push back the character obtained, restore keymaps and use
get-tty-buffer to get the rest of the name.  The function below assumes that
you have the UniPress V2.00 version of gosmacs -- it uses current-local-keymap.
If you have an older version, you'll have to kludge around it.

(defun
    (get-defaulted-buffer-name	default oldmap key buffer
	(setq default (arg 1 ": get-defaulted-buffer-name "))
	(setq oldmap (current-local-keymap)
	(use-local-map "single-char-keymap")
	(setq key "")
	; It's important to use error-occurred here.  Otherwise we could
	; end up with a keymap that leaves us totally helpless!
	(error-occurred
	    (setq key (get-tty-string ""))
	)
	(use-local-map oldmap)
	(if (!= key "")
	    (progn
		(push-back-string key)
		(setq buffer (get-tty-buffer ""))
	    )
	    (setq buffer default)
	)
	buffer
    )
)

(progn i oldmap
    (define-keymap "single-char-keymap")
    (setq oldmap (current-local-keymap))
    (use-local-map "single-char-keymap")
    (setq i 0)
    (while (< i 0200)
	(local-bind-to-key "self-insert-and-exit" i)
	(setq i (+ i 1))
    )
    (use-local-map oldmap)
)

Caveat: I haven't actually tested this code.  However, I've used code very
similar to it for other purposes.

		-- Glenn Skinner
		National Semiconductor, Microcomputer Systems Division
		(408) 733-2600 x 335