+(defvar darkroom-margins 0.15
+ "Margins to use in darkroom-mode.
+
+It's value can be:
+
+- a floating point value betweeen 0 and 1, specifies percentage of
+ window width in columns to use as a margin.
+
+- a cons cell (LEFT RIGHT) specifying the left and right margins
+ in columns.
+
+- a function that returns a cons cell interpreted like the
+ previous option.
+
+Value is effective when `darkroom-minor-mode' is toggled, when
+changing window or by calling `darkroom-set-margins'")
+
+(defvar darkroom-turns-on-visual-line-mode t
+ "If non-nil pair `visual-line-mode' with
+ `darkroom-minor-mode'")
+(defvar darkroom-fringes-outside-margins t
+ "If non-nil use fringes outside margins for `darkroom-minor-mode'")
+
+(defun darkroom-margins ()
+ (cond ((functionp darkroom-margins)
+ (funcall darkroom-margins))
+ ((consp darkroom-margins)
+ darkroom-margins)
+ ((and (floatp darkroom-margins)
+ (< darkroom-margins 1))
+ (let ((delta (darkroom-float-to-columns darkroom-margins)))
+ (cons delta delta)))))
+
+(defun darkroom-float-to-columns (f)
+ (ceiling (* (let ((edges (window-edges)))
+ (- (nth 2 edges) (nth 0 edges)))
+ f)))
+
+(defun darkroom-set-margins (&optional margins)
+ "Adjust margins to `darkroom-margins' or optional MARGINS."
+ (let ((margins
+ (or margins
+ (darkroom-margins))))
+ (when margins
+ (set-window-margins (selected-window) (car margins) (cdr margins)))))
+
+(defun darkroom-increase-margins ()
+ (interactive)
+ (when (floatp darkroom-margins)
+ (setq darkroom-margins (+ 0.05 darkroom-margins))
+ (darkroom-set-margins)))
+
+(defun darkroom-decrease-margins ()
+ (interactive)
+ (when (floatp darkroom-margins)
+ (setq darkroom-margins (- darkroom-margins 0.05))
+ (darkroom-set-margins)))
+
+(defun darkroom-confirm-fill-paragraph ()
+ (interactive)
+ (when (yes-or-no-p "Really fill paragraph?")
+ (call-interactively 'fill-paragraph)))
+
+(defvar darkroom-minor-mode-map (let ((map (make-sparse-keymap)))
+ (define-key map (kbd "C-M-+") 'darkroom-increase-margins)
+ (define-key map (kbd "C-M--") 'darkroom-decrease-margins)
+ (define-key map (kbd "M-q") 'darkroom-confirm-fill-paragraph)
+ map))
+
+(defvar darkroom-saved-mode-line-format nil)
+(defvar darkroom-saved-visual-mode nil)
+(define-minor-mode darkroom-minor-mode
+ "A minor mode that emulates the darkroom editor."
+ nil
+ " dark"
+ nil
+ (cond (darkroom-minor-mode
+ (setq darkroom-saved-mode-line-format mode-line-format
+ mode-line-format nil)
+ (setq fringes-outside-margins darkroom-fringes-outside-margins)
+ (add-hook 'window-configuration-change-hook 'darkroom-set-margins nil t)
+ (darkroom-set-margins)
+ (setq header-line-format t)
+ ;; a hack shoulnd't be needed but apparently is
+ (set-window-buffer (selected-window) (current-buffer))
+ (when darkroom-turns-on-visual-line-mode
+ (visual-line-mode 1)))
+ (t
+ (setq header-line-format nil)
+ (setq mode-line-format darkroom-saved-mode-line-format)
+ (when darkroom-turns-on-visual-line-mode
+ (visual-line-mode -1))
+ (remove-hook 'window-configuration-change-hook 'darkroom-set-margins t)
+ (set-window-margins (selected-window) 0 0))))
+
+
+
+
+(provide 'darkroom)