Emacs – Changing show-paren-mode Areas

elispemacssyntax highlighting

I like show-paren-mode in Emacs, but I would really like to change the highlighting behavior for closing brackets.

That is, I want the opening bracket to be highlighted when the point is on the closing bracket. The default behavior highlights the opening bracket when the point is on the character following the closing bracket.

Is this easy to change? Also, I would be interested in potential benefits of keeping the show-paren-mode behavior as it is.

Best Answer

As of Emacs 24.3, this functionality is not available in Show Paren mode.

Here's some completely untested code (typed directly in my browser) that tweaks Show Paren mode to match a closing parenthesis before the cursor instead of after.

(defadvice show-paren-function 
  (around show-paren-closing-before
          activate compile)
  (if (eq (syntax-class (syntax-after (point))) 5)
      (save-excursion
        (forward-char)
        ad-do-it)
    ad-do-it))

This picks up closing parentheses before the cursor as well, but if the cursor is on a closing parenthesis that follows a closing parenthesis, the closing parenthesis under the cursor has precedence. Fixing this to never look at a closing parenthesis before the cursor looks tricker (it could be done with a gross hack such as (flet ((char-syntax …)) ad-do-it)).

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First of all, in case you don't know about it, Emacs has hexl-find-file which opens up a file in hex editing mode. I know that it's not what you asked for, but if you're already using one, and you're comfortable with Emacs, then it's good to know about it for future needs.

Second, for this kind of "raw" editing of a file (which I tend to do often), find-file-literally is really great. It does what you'd expect it to do, and pretends to be a pre-unicode version of itself and open the file with escapes showing up for non-ascii characters (and control chars etc). This is likely to do what you want, though it does have the obvious disadvantage of not being able to actually read the text if you have a lot of non-ascii content.

So going down further into primitive support, there's the enable-multibyte-characters variable and the set-buffer-multibyte function that is used to toggle it. The nice thing about this is that it changes the buffer presentation dynamically -- for example, try this:

(defun my-multi-toggle ()
  (interactive)
  (set-buffer-multibyte (not enable-multibyte-characters)))
(global-set-key (kbd "C-~") 'my-multi-toggle)

and you now have a key that toggles the raw mode dynamically. It also has the nice property of leaving the cursor in the same place. But this raw mode shows you the internal representation (which looks like UTF-8) and not whatever the file happens to be using as its encoding. It should be possible to do what you're talking about with some hack (for example, using find-file-literally on an open file will ask you about revisiting it, but that resets the location and reloads the file too) -- but it sounds like the above is already fine. (That is, my guess is that you're trying to edit some text field in an otherwise binary file...)

Hide “Mail” in emacs mode line

Just don't enable display-time-mode.

If you do want time, but not Mail, set display-time-mail-string to an empty string:

(setq display-time-mail-string "")

or, better yet:

(custom-set-variables '(display-time-mail-string ""))

Best Answer

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In emacs (or other editor) how to display the byte offset of the cursor

Hide “Mail” in emacs mode line

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