74 lines
2.8 KiB
Org Mode
74 lines
2.8 KiB
Org Mode
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#+TITLE: Cool new scratch buffers
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I had a thought today: It would be nice if I could have more than one
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scratch buffer, and even nicer if they could easily have different
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major modes.
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So, I had this function in my emacs init file, =raise-scratch=:
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#+begin_src emacs-lisp
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(defun raise-scratch ()
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"Show the *scratch* buffer."
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(interactive)
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(switch-to-buffer "*scratch*"))
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#+end_src
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Its nice, it allowed me to do exactly what I wanted to do, easily open
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my scratch buffer. I bound this to ~XF86HomePage~, which makes sense to
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me, since emacs always starts in the ~*scratch*~ buffer.
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Today, though, it didn't seem to be quite enough. As I said, it would
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be nice to have the ability to have multiple scratch buffers with
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different major modes. This is handy for messing around with some
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~sawfish-mode~ code, or ~python-mode~, for example.
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#+begin_src emacs-lisp
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(defun raise-scratch (&optional mode)
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"Show the *scratch* buffer. If called with a universal
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argument, ask the user which mode to use. If MODE is not nil,
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open a new buffer with the name *MODE-scratch* and load MODE as
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its major mode."
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(interactive (list (if current-prefix-arg
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(read-string "Mode: ")
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nil)))
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(let* ((bname (if mode
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(concat "*" mode "-scratch*")
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"*scratch*"))
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(buffer (get-buffer bname)))
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(unless buffer
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(setq buffer (generate-new-buffer bname))
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(with-current-buffer buffer
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(add-file-local-variable-prop-line 'mode (make-symbol mode))
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(set-auto-mode t)
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(goto-char (point-max))
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(newline)))
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(switch-to-buffer buffer)))
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#+end_src
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This is quite a bit bigger. It now takes an optional =mode= argument,
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when it is called interactively it will check if the universal prefix
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argument (~C-u~) was used and if so, asks for the value of =mode=.
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If mode has been specified it will create a new buffer with the name
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~*MODE-scratch*~. It will then insert a file local property line
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specifying the major mode to use and then switches to it.
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It's the first time I'm using a list with the ~interactive~ command, it
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always seemed very alien to me, but it seems quite clear how it works
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now.
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It was a challenge to figure out how I wanted to do this. My first
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idea was to ask for a file extension and match that to
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~auto-mode-alist~, but that has regexps for keys, so not easily matched.
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Then there is the problem of figuring out how to load the right major
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mode in another way, since adding such a file local property line
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happens /after/ the buffer has been loaded, and thus has no effect on
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which major mode is chosen.
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Of course, this approach doesn't ensure the right major mode gets
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chosen, but that's really up to whomever uses it.
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It makes me very happy to use such an extensible editor.
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