elisp: Event Mod
20.8.3 Modifying and Translating Input Events
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Emacs modifies every event it reads according to
‘extra-keyboard-modifiers’, then translates it through
‘keyboard-translate-table’ (if applicable), before returning it from
‘read-event’.
-- Variable: extra-keyboard-modifiers
This variable lets Lisp programs “press” the modifier keys on the
keyboard. The value is a character. Only the modifiers of the
character matter. Each time the user types a keyboard key, it is
altered as if those modifier keys were held down. For instance, if
you bind ‘extra-keyboard-modifiers’ to ‘?\C-\M-a’, then all
keyboard input characters typed during the scope of the binding
will have the control and meta modifiers applied to them. The
character ‘?\C-@’, equivalent to the integer 0, does not count as a
control character for this purpose, but as a character with no
modifiers. Thus, setting ‘extra-keyboard-modifiers’ to zero
cancels any modification.
When using a window system, the program can press any of the
modifier keys in this way. Otherwise, only the <CTL> and <META>
keys can be virtually pressed.
Note that this variable applies only to events that really come
from the keyboard, and has no effect on mouse events or any other
events.
-- Variable: keyboard-translate-table
This terminal-local variable is the translate table for keyboard
characters. It lets you reshuffle the keys on the keyboard without
changing any command bindings. Its value is normally a char-table,
or else ‘nil’. (It can also be a string or vector, but this is
considered obsolete.)
If ‘keyboard-translate-table’ is a char-table (
Char-Tables), then each character read from the keyboard is
looked up in this char-table. If the value found there is
non-‘nil’, then it is used instead of the actual input character.
Note that this translation is the first thing that happens to a
character after it is read from the terminal. Record-keeping
features such as ‘recent-keys’ and dribble files record the
characters after translation.
Note also that this translation is done before the characters are
supplied to input methods (Input Methods). Use
‘translation-table-for-input’ (Translation of Characters),
if you want to translate characters after input methods operate.
-- Function: keyboard-translate from to
This function modifies ‘keyboard-translate-table’ to translate
character code FROM into character code TO. It creates the
keyboard translate table if necessary.
Here’s an example of using the ‘keyboard-translate-table’ to make
‘C-x’, ‘C-c’ and ‘C-v’ perform the cut, copy and paste operations:
(keyboard-translate ?\C-x 'control-x)
(keyboard-translate ?\C-c 'control-c)
(keyboard-translate ?\C-v 'control-v)
(global-set-key [control-x] 'kill-region)
(global-set-key [control-c] 'kill-ring-save)
(global-set-key [control-v] 'yank)
On a graphical terminal that supports extended ASCII input, you can
still get the standard Emacs meanings of one of those characters by
typing it with the shift key. That makes it a different character as
far as keyboard translation is concerned, but it has the same usual
meaning.
Translation Keymaps, for mechanisms that translate event
sequences at the level of ‘read-key-sequence’.
Info Catalog
elisp: Reading One Event
elisp: Reading Input
elisp: Invoking the Input Method