This package implements support for mapping a pair of simultaneously pressed keys to a command and for mapping the same key being pressed twice in quick succession to a command. Such bindings are called "key chords".
Add to your ~/.emacs:
(require 'key-chord)
(key-chord-mode 1)and some chords, for example:
(key-chord-define-global "hj" 'undo)
(key-chord-define-global ",." "<>\C-b")In this package, a "key chord" is two keys pressed simultaneously, or a single key quickly pressed twice.
(Sometimes pressing SHIFT and/or META plus another key is call a chord,
but not here. However, SHIFT plus two normal keys can be a "key chord".)
Key chord mode acts like a global minor mode controlled by the function
key-chord-mode.
Key chord definitions are stored in ordinary key-maps.
The function key-chord-define-global defines a chord in the global
key-map and key-chord-define defines a chord in a specified key-map,
for example for a specific mode.
A TWO-key chord is two distinct keys pressed simultaneously (within one tenth of a second, or so).
Examples:
(key-chord-define-global ",." "<>\C-b")
(key-chord-define-global "hj" 'undo)
(key-chord-define-global [?h ?j] 'undo) ; the same
(key-chord-define-global "jk" 'dabbrev-expand)
(key-chord-define-global "cv" 'reindent-then-newline-and-indent)
(key-chord-define-global "4r" "$")Comma and dot pressed together insert a pair of angle brackets.
h and j pressed together invoke the undo command.
j and k pressed together invoke the dabbrev-expand command.
c and v pressed together insert a newline.
4 and r pressed together insert a dollar sign.
A ONE-key chord is a single key quickly pressed twice (within one third of a second or so).
Examples:
(key-chord-define-global "''" "`'\C-b")
(key-chord-define-global ",," 'indent-for-comment)
(key-chord-define-global "qq" "the ")
(key-chord-define-global "QQ" "The ")Tick (') pressed twice inserts a back-tick and a tick (').
Comma (,) pressed twice indents for and/or inserts a comment.
q pressed twice inserts the word "the ".
Examples: Mode specific chords
(key-chord-define c++-mode-map ";;" "\C-e;")
(key-chord-define c++-mode-map "{}" "{\n\n}\C-p\t")The command key-chord-describe lists currently defined key chords.
The standard command describe-bindings (C-h b) will also show key
chords.
The standard command describe-key (C-h k) will accept a key chord
and show its definition. (Isn't that amazing. There is no explicit
code to carry out this functionality.)
Don't chord key combinations that exists in the languages you typically
write. Otherwise, if you are typing fast, two key intended to be separate
letters might instead trigger a chord.
E.g. uu would be a good chord in Spanish but not in Finnish, and
hj would be a good chord in English but not in Swedish.
Don't rely solely on /usr/dict/words to find unusual combination.
For example cv or fg can be quite common in certain kinds of
programming. Grep your own texts to verify that a combination is unusual.
And don't forget to check both permutations: fg and gf.
Choose two keys that are close to each other on the keyboard, so they can be quickly typed without effort. Chords involving two hands (as opposed to two fingers on one hand) are harder to type (quickly). The idea is that key chords are to replace function keys for functions that are frequently performed while the hands are in writing position.
Key chords might not work well over a slow network.
When recording keyboard macros, the time between keyboard inputs are not
recorded. Thus, the key-chord-input-method cannot know for sure if two keys
in a macro was a chord or not. The current solution remembers the first key
of the chords typed during macro recording, and keys that match those (and
are defined as chords) are considered key-chords during macro execution.
This knowledge is not saved with name-last-kbd-macro, so they may
execute wrong if they contain pair of keys that match defined chords.
Emacs will not call input-method-function for keys that have non numeric
codes or whose code is outside the range 32..126. Thus, you cannot define
key chords involving function keys, control keys, or even your non-english
letters (on national keyboards) that otherwise are well positioned for
chording on your keyboard.
(I think chording left and right arrow keys would be useful, but cannot do.
I consider this a bug in Emacs. Input methods could happily return
unmodified any key they don't know about.)
Key chords longer that 2 keys are not supported. It could be done, but I don't think it is worth the trouble, since most keyboards will not reliably send all key codes when 3 or more keys are pressed simultaneously. It might also be a bit trickier to maintain performance.
Key chord mode uses input-method-function. And so do internationalisation
packages (mule, quail, etc). Do not expect them to work well together.
The last one that gets the input-method-function rules.
Key chords piggy back in ordinary key maps, so they can be defined per mode without having to add hooks to all modes.
Key chord key codes are vectors beginning with the atom key-chord.
A two key chord, e.g. "hj", will add two entries in the key-map.
E.g. [key-chord ?h ?j] and [key-chord ?j ?h].
When key-chord-mode is enabled input-method-function is set to
key-chord-input-method.