I don't mind if the occasional code line runs long. For example, the Shopify ruby standard allows lines of 120. But I want comments to be restricted to the first 78 lines or so. Is there any way in a programming major mode to have a different fill column for comment lines than for code line?
OK. With some prodding from @wvxvw, I looked at some source code, though the code for fill-paragraph rather than ruby-mode. There is a function for filling comments, but it does not take a fill-column parameter. So, I tried the following advice, which appears to do the trick:
(defvar ded:fill-column-for-progs 78)
(defun ded:prog-fill-paragraph (orig-fun &rest args)
(let ((fill-column ded:fill-column-for-progs))
(apply orig-fun args)))
(advice-add 'fill-comment-paragraph :around #'ded:prog-fill-paragraph)
The ded: is just my personal prefix. So far, so good. It even uses justification when used with the universal argument.
C-x fto change the fill-column here or there. ThenM-qto re-fill. – Drew Sep 11 '20 at 22:31fill-paragraph-functionandfill-forward-paragraph-functionset to? Emacs actually has some logic for filling comments differently than the code, but it may not be relevant in your case, ifruby-modeoverrides the default behavior (which it probably does). Anyways, my approach would be to look forruby-mode's function to fill paragraph, and see if it is possible to extend / replace it with something of your own design that deals with comments the way you want. – wvxvw Sep 13 '20 at 6:58