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This section describes keymaps that are used during reading a key sequence,
to translate certain event sequences into others. read-key-sequence
checks every subsequence of the key sequence being read, as it is read,
against function-key-map and then against key-translation-map.
This variable holds a keymap that describes the character sequences sent by function keys on an ordinary character terminal. This keymap has the same structure as other keymaps, but is used differently: it specifies translations to make while reading key sequences, rather than bindings for key sequences.
If function-key-map “binds” a key sequence k to a vector
v, then when k appears as a subsequence anywhere in a key
sequence, it is replaced with the events in v.
For example, VT100 terminals send <ESC> O P when the keypad
<PF1> key is pressed. Therefore, we want Emacs to translate that
sequence of events into the single event pf1. We accomplish this by
“binding” <ESC> O P to [pf1] in function-key-map,
when using a VT100.
Thus, typing C-c <PF1> sends the character sequence C-c
<ESC> O P; later the function read-key-sequence translates this
back into C-c <PF1>, which it returns as the vector [?\C-c
pf1].
Entries in function-key-map are ignored if they conflict with
bindings made in the minor mode, local, or global keymaps. The intent is
that the character sequences that function keys send should not have command
bindings in their own right—but if they do, the ordinary bindings take
priority.
The value of function-key-map is usually set up automatically
according to the terminal's Terminfo or Termcap entry, but sometimes those
need help from terminal-specific Lisp files. Emacs comes with
terminal-specific files for many common terminals; their main purpose is to
make entries in function-key-map beyond those that can be deduced
from Termcap and Terminfo. Voir la section Terminal-Specific Initialization.
This variable is another keymap used just like function-key-map to
translate input events into other events. It differs from
function-key-map in two ways:
key-translation-map goes to work after function-key-map is
finished; it receives the results of translation by function-key-map.
key-translation-map override actual key
bindings. For example, if C-x f has a non-prefix binding in
key-translation-map, that translation takes effect even though
C-x f also has a key binding in the global map.
Note however that actual key bindings can have an effect on
key-translation-map, even though they are overridden by it. Indeed,
actual key bindings override function-key-map and thus may alter the
key sequence that key-translation-map receives. Clearly, it is
better to avoid this type of situation.
The intent of key-translation-map is for users to map one character
set to another, including ordinary characters normally bound to
self-insert-command.
You can use function-key-map or key-translation-map for more
than simple aliases, by using a function, instead of a key sequence, as the
“translation” of a key. Then this function is called to compute the
translation of that key.
The key translation function receives one argument, which is the prompt that
was specified in read-key-sequence—or nil if the key
sequence is being read by the editor command loop. In most cases you can
ignore the prompt value.
If the function reads input itself, it can have the effect of altering the event that follows. For example, here's how to define C-c h to turn the character that follows into a Hyper character:
(defun hyperify (prompt)
(let ((e (read-event)))
(vector (if (numberp e)
(logior (lsh 1 24) e)
(if (memq 'hyper (event-modifiers e))
e
(add-event-modifier "H-" e))))))
(defun add-event-modifier (string e)
(let ((symbol (if (symbolp e) e (car e))))
(setq symbol (intern (concat string
(symbol-name symbol))))
(if (symbolp e)
symbol
(cons symbol (cdr e)))))
(define-key function-key-map "\C-ch" 'hyperify)
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If you have enabled keyboard character set decoding using
set-keyboard-coding-system, decoding is done after the translations
listed above. Voir la section Terminal I/O Encoding. However, in future Emacs
versions, character set decoding may be done at an earlier stage.
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Ce document a été généré par Eric Reinbold le 13 Octobre 2007 en utilisant texi2html 1.78.