Bozhidar Batsov over at Emacs Redux has taken some time off from his open source projects such as rubocop, nrepl, cider, prelude, projectile, and many others to write a useful post on the various Emacs commenting commands. It turns out that there are a lot of them but like most of you, I long ago settled on comment-dwim (bound to Meta+;) because I thought it handled all my normal commenting needs more or less automatically. It was nice to need to remember only one command that handles everything.
I said “thought it handled” rather than “think it handles” because Batsov’s post mentioned another command I didn’t know about: comment-line. It handles all the cases I care about that comment-dwim does but also handles deleting the comment on the current line, which is a bit clumsy with comment-dwim. Batsov says he much prefers comment-line and has changed the Meta+; binding to run it instead.
The other commenting command that I occasionally find useful is comment-box. I like to use it for section headers or just before C functions. What I don’t like about it is that the width of the box is scaled to fit the comment width. I prefer to have it spread across the page width. I wrote about that here but the code is short so here it is again in case anyone is interested:
(defun jcs-comment-box (b e) "Draw a box comment around the region but arrange for the region to extend to at least the fill column. Place the point after the comment box." (interactive "r") (let ((e (copy-marker e t))) (goto-char b) (end-of-line) (insert-char ? (- fill-column (current-column))) (comment-box b e 1) (goto-char e) (set-marker e nil)))
As Batsov says, comments are an important part of programming and it’s worth learning the tools that Emacs provides to make using them easier. Take a look at his post to see what’s available.