Is it possible to configure multi-line comments to comment/uncomment selected text?
For example C/C++'s preprocessor could be toggled like this.
eg:
Before:
// a comment
Some(code); /* some comment */
After:
#if 0
// a comment
Some(code); /* some comment */
#endif
Since C/C++ don't support nested comments, I find this preferable behavior to quickly disable chunks of code.
This can be done by matching the beginning & end of the region, removing when found, adding when not found.
The following example is a generic function which takes arguments which can be set for each major-mode.
(defun my-comment-multi-line-toggle--impl (head tail head-regex tail-regex)
"Utility for toggling multi-line comments.
Argument HEAD Start of multi-line comment.
Argument TAIL End of multi-line comment.
Argument HEAD-REGEX Match the start of a multi-line comment.
Argument TAIL-REGEX Match the end of a multi-line comment."
(unless (use-region-p)
(user-error "No active region"))
(let ((beg (region-beginning))
(end (region-end))
(match-head nil)
(match-tail nil)
;; Prevent local language settings
;; impacting basic space stepping.
(syntax-table (make-syntax-table)))
(save-excursion
(with-syntax-table syntax-table
;; True when we have multi-line comments.
(if (and (setq match-head
(save-match-data
(goto-char beg)
(skip-chars-forward "[:blank:]")
(when (looking-at head-regex)
(match-data))))
(setq match-tail
(save-match-data
(goto-char end)
(skip-chars-backward "[:blank:]")
(when (looking-back tail-regex)
(match-data))))
;; Double check there is no overlap.
(<= (save-match-data
(set-match-data match-head)
(match-end 0))
(save-match-data
(set-match-data match-tail)
(match-beginning 0))))
;; Remove multi-line comment.
(dolist (match (list match-tail match-head))
(save-match-data
(set-match-data match)
(goto-char (match-beginning 0))
(replace-match "" t nil nil))
(beginning-of-line)
(when (looking-at-p "[[:blank:]]*$")
(kill-whole-line)))
;; Add multi-line comment.
(goto-char end)
(insert tail)
(indent-according-to-mode)
(insert "\n")
(goto-char beg)
(insert head)
(indent-according-to-mode)
(insert "\n"))))))
(defun my-comment-multi-line-toggle (&optional head tail head-regex tail-regex)
"Toggle multi-line comments for various languages."
(interactive)
(cond
;; Support optionally passing in arguments.
((and head tail head-regex tail-regex)
(my-comment-multi-line-toggle--impl
head tail head-regex tail-regex))
((memq major-mode '(c-mode c++-mode glsl-mode))
(my-comment-multi-line-toggle--impl
"#if 0"
"#endif"
"^[[:blank:]]*#[[:blank:]]*if[[:blank:]]+0[[:blank:]]*$"
"^[[:blank:]]*#[[:blank:]]*endif[[:blank:]]*$"))
((memq major-mode '(lua-mode))
(my-comment-multi-line-toggle--impl
"--[["
"]]"
"^[[:blank:]]*\\-\\-\\[\\[[[:blank:]]*$"
"^[[:blank:]]*\\]\\][[:blank:]]*$"))
((memq major-mode '(cmake-mode))
(my-comment-multi-line-toggle--impl
"#[["
"]]"
"^[[:blank:]]*#\\[\\[[[:blank:]]*$"
"^[[:blank:]]*\\]\\][[:blank:]]*$"))
((memq major-mode '(python-mode))
(my-comment-multi-line-toggle--impl
"'''"
"'''"
"^[[:blank:]]*\\('''\\|\"\"\"\\)[[:blank:]]*$"
"^[[:blank:]]*\\('''\\|\"\"\"\\)[[:blank:]]*$"))
(t
(user-error "Multi-line comment unsupported major mode '%s'" major-mode))))
