Added a very basic Sass emacs mode.

git-svn-id: svn://hamptoncatlin.com/haml/trunk@414 7063305b-7217-0410-af8c-cdc13e5119b9

extra/sass-mode.el

@@ -0,0 +1,158 @@
+;;; sass-mode.el -- Major mode for editing Sass files
+;;; Version 0.0.1
+;;; Written by Nathan Weizenbaum
+
+;;; Because Sass's indentation schema is similar
+;;; to that of YAML and Python, many indentation-related
+;;; functions are similar to those in yaml-mode and python-mode.
+
+;;; To install, save this somewhere and add the following to your .emacs file:
+;;; 
+;;; (add-to-list 'load-path "/path/to/sass-mode.el")
+;;; (require 'sass-mode nil 't)
+;;; 
+
+;;; Code:
+
+;; User definable variables
+
+(defgroup sass nil
+  "Support for the Sass template language."
+  :group 'languages
+  :prefix "sass-")
+
+(defcustom sass-mode-hook nil
+  "*Hook run by `sass-mode'."
+  :type 'hook
+  :group 'sass)
+
+(defcustom sass-indent-offset 2
+  "*Amount of offset per level of indentation."
+  :type 'integer
+  :group 'sass)
+
+(defcustom sass-backspace-function 'backward-delete-char-untabify
+  "*Function called by `sass-electric-backspace' when deleting backwards."
+  :type 'function
+  :group 'sass)
+
+(defface sass-tab-face
+   '((((class color)) (:background "red" :foreground "red" :bold t))
+     (t (:reverse-video t)))
+  "Face to use for highlighting tabs in Sass files."
+  :group 'faces
+  :group 'sass)
+
+;; Helper Functions
+
+(defun string-* (str n)
+  "Concatenates a string with itself n times."
+  (if (= n 0) ""
+    (concat str (string-* str (- n 1)))))
+
+(defun sre (str)
+  "Prepends a Sass-tab-matching regexp to str."
+  (concat "^\\(" (string-* " " sass-indent-offset) "\\)*" str))
+
+;; Constants
+
+(defconst sass-mode-version "0.0.1" "Version of `sass-mode.'")
+
+(defconst sass-blank-line-re "^[ \t]*$"
+  "Regexp matching a line containing only whitespace.")
+
+(defconst sass-full-attr-re (sre ":[^ \t]*[ \t]*[^ \t]")
+  "Regexp matching a Sass attribute with content.")
+
+;; Mode setup
+
+(defvar sass-mode-map ()
+  "Keymap used in `sass-mode' buffers.")
+(if sass-mode-map
+    nil
+  (setq sass-mode-map (make-sparse-keymap))
+  (define-key sass-mode-map [backspace] 'sass-electric-backspace)
+  (define-key sass-mode-map "\C-?" 'sass-electric-backspace)
+  (define-key sass-mode-map "\C-j" 'newline-and-indent))
+
+(defvar sample-font-lock-keywords
+  '(("function \\(\\sw+\\)" (1 font-lock-function-name-face)))
+  "Keyword highlighting specification for `sample-mode'.")
+
+(define-derived-mode sass-mode fundamental-mode "Sass"
+  "Simple mode to edit Sass.
+
+\\{sass-mode-map}"
+  (set (make-local-variable 'indent-line-function) 'sass-indent-line)
+  (set (make-local-variable 'font-lock-defaults) '(sample-font-lock-keywords)))
+
+;; Font-lock support
+
+(defvar sass-font-lock-keywords
+  (list
+   (cons sass-tag-re '(1 font-lock-function-name-face))
+   '("function \\(\\sw+\\)" (1 font-lock-function-name-face))
+   '("^[\t]+" 0 'sass-tab-face t))
+   "Expressions to highlight in Sass mode.")
+
+;; Indentation and electric keys
+
+(defun sass-compute-indentation ()
+  "Calculate the maximum sensible indentation for the current line."
+  (save-excursion
+    (beginning-of-line)
+    (if (bobp) 10
+      (forward-line -1)
+      (while (and (looking-at sass-blank-line-re)
+                  (> (point) (point-min)))
+        (forward-line -1))
+      (+ (current-indentation)
+         (if (not (looking-at sass-full-attr-re))
+             sass-indent-offset 0)))))
+
+(defun sass-indent-line ()
+  "Indent the current line.
+The first time this command is used, the line will be indented to the
+maximum sensible indentation.  Each immediately subsequent usage will
+back-dent the line by `sass-indent-offset' spaces.  On reaching column
+0, it will cycle back to the maximum sensible indentation."
+  (interactive "*")
+  (let ((ci (current-indentation))
+        (cc (current-column))
+        (need (sass-compute-indentation)))
+    (save-excursion
+      (beginning-of-line)
+      (delete-horizontal-space)
+      (if (and (equal last-command this-command) (/= ci 0))
+          (indent-to (* (/ (- ci 1) sass-indent-offset) sass-indent-offset))
+        (indent-to need)))
+      (if (< (current-column) (current-indentation))
+          (forward-to-indentation 0))))
+
+(defun sass-electric-backspace (arg)
+  "Delete characters or back-dent the current line.
+If invoked following only whitespace on a line, will back-dent to the
+immediately previous multiple of `sass-indent-offset' spaces."
+  (interactive "*p")
+  (if (or (/= (current-indentation) (current-column)) (bolp))
+      (funcall sass-backspace-function arg)
+    (let ((ci (current-column)))
+      (beginning-of-line)
+      (delete-horizontal-space)
+      (indent-to (* (/ (- ci (* arg sass-indent-offset))
+                       sass-indent-offset)
+                    sass-indent-offset)))))
+
+;; Setup/Activation
+
+(defun sass-mode-version ()
+  "Diplay version of `sass-mode'."
+  (interactive)
+  (message "sass-mode %s" sass-mode-version)
+  sass-mode-version)
+
+(provide 'sass-mode)
+
+(add-to-list 'auto-mode-alist '("\\.sass\\'" . sass-mode))
+
+;;; sass-mode.el ends here