Which Function Mode

Here’s another useful feature in Emacs that lurks in the back of the cupboard, rarely seeing the light of day.

There’s a minor mode, which-function-mode, that shows the current defun – Lisp lingo for a function, but Emacs-speak for anything that would count as one – in your modeline by looking at where your point is.

The mode is global and it works in most major modes that implement M-x imenu support. If you have never used imenu, you should read my article on effective movement.

Nevertheless, to err on the side of caution, the which-function-mode only activates if the major mode is in the which-func-modes list.

To add or remove items you can use the customize interface: M-x customize-option RET which-func-modes RET and alter the list of major modes you want it to use. Note that not all major modes work with it, of course. If you’re unsure of the exact name of a major mode, type M-: major-mode — note the lack of parentheses!

To turn the mode on automatically you can enable it in the which-func group: M-x customize-group RET which-func RET.