Question

I’m using the following snippet to set a 1-character margin to both edges of an Emacs buffer (thanks to zev!):

(add-hook 'window-configuration-change-hook
      (lambda ()
        (set-window-margins (car (get-buffer-window-list (current-buffer) nil t)) 1 1)))

However, I’d also like to have another configuration that gives me very wide left and right margins (say, 30 chars). How could I assign a hotkey for toggling between these two states, possibly over all buffers?

I tried the following:

(global-set-key [(control f10)]
(add-hook 'window-configuration-change-hook
      (lambda ()
        (set-window-margins (car (get-buffer-window-list (current-buffer) nil t)) 30 30))))

But got this error:

Wrong type argument: commandp, ((lambda nil (set-window-margins (car (get-buffer-window-list (current-buffer) nil t)) 30 30)) (lambda nil (set-window-margins (car (get-buffer-window-list (current-buffer) nil t)) 1 1)) frame-local-variables-check)

Where am I wrong? Thanks for any explanations. Cheers!

EDIT:

I am well aware of darkroom-mode that provides such wide margins. But it doesn’t seem to work flawlessly on my XP.

Answer 1

This should get you going:

(global-set-key [C-f10]
     (lambda ()
     (interactive)
     (set-window-margins (car (get-buffer-window-list (current-buffer) nil t)) 30 30)))

Your example does not work as the global-set-key is expecting the second argument to be a command, hence the error. Also your key definiton is a little odd.

For your comment:

(walk-windows (lambda (window) (set-window-margins window 30 30)) nil t)