Writing GNU Emacs Extensions

Keys and Strings

The goal of this chapter is to make any BS-generating key work the same as any DEL-generating key. Unfortunately, C-h will no longer invoke the Help command. You'll need to choose some other key to invoke Help; my own choice for the new Help key is META-question-mark.

The META Key

The META key works like the CONTROL key and the SHIFT key, which means that you hold it down while pressing some other key. Such keys are called modifiers. Not all keyboards have a META key, though. Sometimes the ALT key will serve the same purpose, but not all keyboards have an ALT key, either.

In any case, you don't need to use the META key or the ALT key. The single keystroke META-x can always be replaced with the two-key sequence ESC x. (Note that ESC is not a modifier—you press it and release it like a normal key before pressing x.)

Binding Keystrokes to Commands

In Emacs, every keystroke invokes a command or is part of a multiple-key sequence that invokes a command. Commands are special kinds of Lisp functions, as we will see. Making a keystroke invoke a command such as Help is known as binding the keysequence to the command. We'll need to execute some Lisp code to bind keys to commands. One Lisp function for doing this is global-set-key.

Here's what a call to global-set-key looks like. Remember that a function call in Lisp is simply a parenthesized list. The first element of the list is the name of the function, and any remaining elements are the arguments. The function global-set-key ...