Monthly Archives: January 2009

Emacs Tidbit: Console or GUI?

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Emacs has two different UIs: one using only a text console, the other using the window system. Even when a window system is present, Emacs can be started in a terminal emulator with the -nw option to show its text UI.

There are some customizations you might want to make conditional on the kind of UI. In my case, I use ECB, and in general I’d like it to start up automatically when I launch Emacs, but only when running in GUI mode.

It’s pretty simple to achieve this, a small addition to ~/.emacs does the trick.

(if (memq window-system '(x w32 mac))
  (ecb-activate))

Line movement for Emacs

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Recently, I’ve been mingling with two old acquaintances (if not downright friends): C and Emacs. Through my interaction with other text editors I’ve come to know functions to move the current line, i.e. the one containing the cursor, up or down. That’s something I wanted to have in Emacs too. And so I wrote my first ever Emacs Lisp functions with some help from comp.emacs.

Stick these definitions in ~/.emacs and evaluate them or restart Emacs.

(defun move-line-down ()
  (interactive)
  (let ((col (current-column)))
    (save-excursion
      (next-line)
      (transpose-lines 1))
    (next-line)
    (move-to-column col)))

(defun move-line-up ()
  (interactive)
  (let ((col (current-column)))
    (save-excursion
      (next-line)
      (transpose-lines -1))
    (move-to-column col)))

(global-set-key [\M-down] 'move-line-down)
(global-set-key [\M-up] 'move-line-up)

Now you have Meta-Down and Meta-Up (i.e., probably Alt-Down and Alt-Up) bound to moving the current line around.