This page shows you how to remap keys to input Unicode symbols using the elisp function “key-translation-map”, and discuss some related issues.
Recently i wrote a article on How to Create a APL or Math Symbols Keyboard Layout. In the article, i described several ways to create a math symbols layout for inputting math symbols for Mac, Windows, Linux. Some are OS-wide thru OS's user-configurable mechanisms. Some are using key-macro software for that OS. And there's emacs for just within emacs on any OS. I've used them all in the past 2 decades, but in the past few years, i find the most practical and flexible way is just emacs. Because: ① 99% of my typing are done in emacs. So, i don't really need them to be OS-wide. ② Each method of remapping keys all have their own limitations (⁖ on Mac ＆ Windows, there's no way to remap some key combinations.), but within emacs it has the most support on remapping keys that has less restrictions than using OS's methods.
Here's interesting thing i discovered recently particular to emacs.
If you want to define a key combo for inserting a Unicode char such as math symbol λ, you can do it using global-set-key or “key-translation-map”.
Example of using global-set-key:
(global-set-key (kbd "H-3") (lambda () (interactive) (insert "λ"))) ; 【Hyper+3】 insert λ char (global-set-key (kbd "H-3") "λ") ; 【Hyper+3】 insert λ char. This is a built-in macro for above.
(In this example we use Hyper key, but Ctrl or Meta works too. You can make the ❖ Win key or the ▤ Menu key act as Hyper. To set up, see: Emacs: How to define Super ＆ Hyper Keys.)
Example of using “key-translation-map”:
(define-key key-translation-map (kbd "H-3") (kbd "λ")) ; 【Hyper+3】 insert λ char
There are some advantage and disadvantages in either way.
If you use global-set-key, then when you do interactive search 【Ctrl+s】, then when you type 【Hyper+3】, it'll exit the search. So this means, if you use Unicode heavily in your files, then you lose the ability to isearch them. (you can work-around by typing it in the buffer first, put cursor on it, start isearch, 【Ctrl+w】 to select the char. Then when done, delete that character you inserted for this purpose.)
Using “key-translation-map” doesn't have this problem.
The problem with “key-translation-map” is this:
Suppose you don't type the backtick (`) char often, and you press 【Ctrl+x o】 delete-other-windows ≈50 times more often. So, to increase the efficiency of key use on keyboard, you remap backtick to do delete-other-windows and set 【Hyper+`】 for inputting the backtick. The elisp code looks like this:
(global-set-key (kbd "`") 'someCommand) ; set ` to someCommand (define-key key-translation-map (kbd "H-`") (kbd "`")) ; insert backtick char by 【Hyper+`】
The problem is, when you type 【Hyper+`】, it'll actually call the command bound to backtick.
So, this means, the “key-translation-map” is great for symbol input but is not good if you want to use it as a way to remap buttons.
Note: there's the function keyboard-translate. However, it is designed to translate character only. So, key combination isn't a character and you can't use it for Hyper combination. Using (define-key key-translation-map …) is more versatile. (Due to historical reasons, keyboard-translate does work for some Ctrl combination key. (thanks to
Stefan Monnier and Deniz Dogan
for this tip. (Source groups.google.com)))
Using proper symbols can decreases ambiguity at syntax level. I use Unicode a lot, all over, in my writings, as well in coding.
For example, bullet (•), “curly quote”, dash (—), angle bracket for 〈article title〉 and 《book title》 〔☛ Intro to Chinese Punctuation〕, and i use 【lenticular bracket】 to mark key combinations, 「corner bracket」 to mark computer code, and i use FULLWIDTH AMPERSAND (＆) to avoid HTML entity complexity 〔☛ HTML Entities, Ampersand, Unicode, Semantics〕 , and lots others.
Using proper symbols decreases ambiguity at syntax level. For example, the ASCII asterisk (*) can mean lots of things. But a dedicated bullet “•” carries a precise semantics.
For coding, some languages heavily use math symbols (⁖ APL, Mathematica). For functional languages such as Haskell, Scheme Lisp, you can setup for example “λ” to mean “lambda”, “≠” to mean “!=”, “⊕” for user-defined operators, etc. You can also use symbols for variable names in emacs lisp,
JavaScript, Java (⁖ α = 3 instead of alpha = 3). See:
For more articles on keyboarding, see: Keyboards, Layouts, Hotkeys, Macros, RSI. For Unicode, see Unicode Tutorial.