26.6.3 Emacs Lisp Documentation Lookup

When editing Emacs Lisp code, you can use the commands C-h f ( describe-function) and C-h v ( describe-variable) to view the built-in documentation for the Lisp functions and variables that you want to use. See Help by Command or Variable Name.

ElDoc is a buffer-local minor mode that helps with looking up Lisp documentation. When it is enabled, the echo area displays some useful information whenever there is a Lisp function or variable at point; for a function, it shows the argument list, and for a variable it shows the first line of the variable’s documentation string. To toggle ElDoc mode, type M-x eldoc-mode. There’s also a Global ElDoc mode, which is turned on by default, and affects buffers whose major mode sets the variables described below. Use M-x global-eldoc-mode to turn it off globally.

These variables can be used to configure ElDoc mode:

eldoc-documentation-strategy

This variable holds the function which is used to retrieve documentation for the item at point from the functions in the hook eldoc-documentation-functions. By default, eldoc-documentation-strategy returns the first documentation string produced by the eldoc-documentation-functions hook, but it may be customized to compose those functions’ results in other ways.

eldoc-documentation-functions

This abnormal hook holds documentation functions. It acts as a collection of backends for ElDoc. This is what modes should use to register their documentation functions with ElDoc.

eldoc-display-truncation-message

If non- nil (the default), display a verbose message about how to view a complete documentation (if it has been truncated in the echo area). If nil, just mark truncated messages with ‘ ...’.