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Re: Alt as meta, except for certain keys, how?

From: Kevin Rodgers
Subject: Re: Alt as meta, except for certain keys, how?
Date: Tue, 12 Aug 2003 11:14:17 -0600
User-agent: Mozilla/5.0 (X11; U; SunOS i86pc; en-US; rv: Gecko/20020406 Netscape6/6.2.2

Jussi Piitulainen wrote:

Kevin Rodgers writes:
So you need to use the vector notation for keys containing
meta-modified non-ASCII characters:

(define-key key-translation-map [?\M- ...] ...)

M-space? Anyway, that did not seem to work when I tried it. The key
remained unbound.

Sorry, I was trying to show a general form via ellipses.  A concrete example
would be

(define-key key-translation-map [?\M-7] "|")

Is there a way to turn every valid key code into an
Escape-Meta-Alt-Control-Shift-something? Or can I use a numeric key
code with function-key-map?

I don't understand your question.

I'm sorry. A concrete instance of the first question is this. I'll
write "letter" for the non-ASCII letters. The following works:

   (define-key key-translation-map [-134217482] "o")

I would like to find out a more transparent syntax for that number;
text-char-description does not do it. Things like [?\M-letter] and
[?\M- ?letter] and [(meta ?letter)] do not seem to work.

I don't know why those wouldn't work (except that the extra space and
question mark between ?M- and letter in the first form are wrong), unless
there are keyboard/buffer/file coding issues.  You might want to use the
octal encoding instead:

[?\M-\241] ; meta inverted exclamation point

For the second question I know the answer now: the following works.

   (global-unset-key [-134217500])
   (define-key function-key-map [-134217500] "a")

I got these numbers by pressing the key I want to bind: Alt-letter,
where Alt is Meta and letter is outside ASCII. However, ?\M-letter
evaluates to -134215434 rather than -134217482. If I omit to set
mac-keyboard-text-encoding to Latin-1, ?\M-letter evaluates to
-134217574, which is again something else (and the key in question
cannot be used to produce the letter any more).

I don't understand Emacs' encoding scheme at all, nor do I want to.

"\M-letter" evaluates to a string that contains just the letter.

The only meta characters that can be included in a string are the meta-

modified ASCII characters:

|    In a string, the 2**7 bit attached to an ASCII character indicates a
| meta character; thus, the meta characters that can fit in a string have
| codes in the range from 128 to 255, and are the meta versions of the
| ordinary ASCII characters.

That's why you have to use the vector notation.

I think I'll use the numbers for these few keys.

The "Character Type" node of the Emacs Lisp manual strongly discourages that:

|    Since characters are really integers, the printed representation of a
| character is a decimal number.  This is also a possible read syntax for
| a character, but writing characters that way in Lisp programs is a very
| bad idea.  You should _always_ use the special read syntax formats that
| Emacs Lisp provides for characters.  These syntax formats start with a
| question mark.

Kevin Rodgers

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