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+;;; less-css-mode.el --- Major mode for editing LESS CSS files (lesscss.org)
+;;
+;; Copyright (C) 2011-2014 Steve Purcell
+;;
+;; Author: Steve Purcell <steve@sanityinc.com>
+;; URL: https://github.com/purcell/less-css-mode
+;; Keywords: less css mode
+;; Version: DEV
+;;
+;; This program is free software; you can redistribute it and/or
+;; modify it under the terms of the GNU General Public License as
+;; published by the Free Software Foundation; either version 2 of
+;; the License, or (at your option) any later version.
+;;
+;; This program is distributed in the hope that it will be
+;; useful, but WITHOUT ANY WARRANTY; without even the implied
+;; warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+;; PURPOSE.  See the GNU General Public License for more details.
+;;
+;;; Commentary:
+;;
+;; This mode provides syntax highlighting for LESS CSS files, plus
+;; optional support for compilation of .less files to .css files at
+;; the time they are saved: use `less-css-compile-at-save' to enable
+;; this.
+;;
+;; Command line utility "lessc" is required if setting
+;; `less-css-compile-at-save' to t.  To install "lessc" using the
+;; Node.js package manager, run "npm install less"
+;;
+;; Also make sure the "lessc" executable is in Emacs' PATH, example:
+;; (setq exec-path (cons (expand-file-name "~/.gem/ruby/1.8/bin") exec-path))
+;; or customize `less-css-lessc-command' to point to your "lessc" executable.
+;;
+;; We target lessc >= 1.4.0, and thus use the `--no-color' flag by
+;; default.  You may want to adjust `less-css-lessc-options' for
+;; compatibility with older versions.
+;;
+;; `less-css-mode' is derived from `css-mode', and indentation of
+;; nested blocks may not work correctly with versions of `css-mode'
+;; other than that bundled with recent Emacs.
+;;
+;; You can specify per-file values for `less-css-compile-at-save',
+;; `less-css-output-file-name' or `less-css-output-directory' using a
+;; variables header at the top of your .less file, e.g.:
+;;
+;; // -*- less-css-compile-at-save: t; less-css-output-directory: "../css" -*-
+;;
+;; Alternatively, you can use directory local variables to set the
+;; default value of `less-css-output-directory' for your project.
+;;
+;; In the case of files which are included in other .less files, you
+;; may want to trigger the compilation of a "master" .less file on
+;; save: you can accomplish this with `less-css-input-file-name',
+;; which is probably best set using directory local variables.
+;;
+;; If you don't need CSS output but would like to be warned of any
+;; syntax errors in your .less source, consider using `flymake-less':
+;; https://github.com/purcell/flymake-less
+;;
+;;; Credits
+;;
+;; The original code for this mode was, in large part, written using
+;; Anton Johansson's scss-mode as a template -- thanks Anton!
+;; https://github.com/antonj
+;;
+;;; Code:
+
+(require 'derived)
+(require 'compile)
+
+;; There are at least three css-mode.el implementations, but we need
+;; the right one in order to work as expected, not the versions by
+;; Landström or Garshol
+
+(require 'css-mode)
+(unless (or (boundp 'css-navigation-syntax-table)
+            (functionp 'css-smie-rules))
+  (error "Wrong css-mode.el: please use the version by Stefan Monnier, bundled with Emacs >= 23"))
+
+(defgroup less-css nil
+  "Less-css mode"
+  :prefix "less-css-"
+  :group 'css)
+
+;;;###autoload
+(defcustom less-css-lessc-command "lessc"
+  "Command used to compile LESS files.
+Should be lessc or the complete path to your lessc executable,
+  e.g.: \"~/.gem/ruby/1.8/bin/lessc\""
+  :type 'file
+  :group 'less-css
+  :safe 'stringp)
+
+;;;###autoload
+(defcustom less-css-compile-at-save nil
+  "If non-nil, the LESS buffers will be compiled to CSS after each save."
+  :type 'boolean
+  :group 'less-css
+  :safe 'booleanp)
+
+;;;###autoload
+(defcustom less-css-lessc-options '("--no-color")
+  "Command line options for less executable.
+
+Use \"-x\" to minify output."
+  :type '(repeat string)
+  :group 'less-css
+  :safe t)
+
+;;;###autoload
+(defcustom less-css-output-directory nil
+  "Directory in which to save CSS, or nil to use the LESS file's directory.
+
+This path is expanded relative to the directory of the LESS file
+using `expand-file-name', so both relative and absolute paths
+will work as expected."
+  :type 'directory
+  :group 'less-css
+  :safe 'stringp)
+
+;;;###autoload
+(defcustom less-css-output-file-name nil
+  "File name in which to save CSS, or nil to use <name>.css for <name>.less.
+
+This can be also be set to a full path, or a relative path.  If
+the path is relative, it will be relative to the value of
+`less-css-output-dir', if set, or the current directory by
+default."
+  :type 'file
+  :group 'less-css
+  :safe 'stringp)
+(make-variable-buffer-local 'less-css-output-file-name)
+
+;;;###autoload
+(defcustom less-css-input-file-name nil
+  "File name which will be compiled to CSS.
+
+When the current buffer is saved `less-css-input-file-name' file
+will be compiled to css instead of the current file.
+
+Set this in order to trigger compilation of a \"master\" .less
+file which includes the current file.  The best way to set this
+variable in most cases is likely to be via directory local
+variables.
+
+This can be also be set to a full path, or a relative path. If
+the path is relative, it will be relative to the the current directory by
+default."
+  :type 'file
+  :group 'less-css
+  :safe 'stringp)
+(make-variable-buffer-local 'less-css-input-file-name)
+
+(defconst less-css-default-error-regex
+  "^\\(?:\e\\[31m\\)?\\([^\e\n]*\\|FileError:.*\n\\)\\(?:\e\\[39m\e\\[31m\\)? in \\(?:\e\\[39m\\)?\\([^ \r\n\t\e]+\\)\\(?:\e\\[90m\\)?\\(?::\\| on line \\)\\([0-9]+\\)\\(?::\\|, column \\)\\([0-9]+\\):?\\(?:\e\\[39m\\)?")
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Compilation to CSS
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(add-to-list 'compilation-error-regexp-alist-alist
+             (list 'less-css less-css-default-error-regex 2 3 4 nil 1))
+(add-to-list 'compilation-error-regexp-alist 'less-css)
+
+
+(defun less-css-compile-maybe ()
+  "Run `less-css-compile' if `less-css-compile-at-save' is non-nil."
+  (if less-css-compile-at-save
+      (less-css-compile)))
+
+(defun less-css--output-path ()
+  "Calculate the path for the compiled CSS file created by `less-css-compile'."
+  (expand-file-name (or less-css-output-file-name
+                        (concat (file-name-nondirectory (file-name-sans-extension buffer-file-name)) ".css"))
+                    (or less-css-output-directory default-directory)))
+
+(defun less-css--maybe-shell-quote-command (command)
+  "Selectively shell-quote COMMAND appropriately for `system-type'."
+  (funcall (if (eq system-type 'windows-nt)
+               'identity
+             'shell-quote-argument) command))
+
+;;;###autoload
+(defun less-css-compile ()
+  "Compiles the current buffer to css using `less-css-lessc-command'."
+  (interactive)
+  (message "Compiling less to css")
+  (let ((compilation-buffer-name-function (lambda (mode-name) "*less-css-compilation*")))
+    (save-window-excursion
+      (with-current-buffer
+          (compile
+           (mapconcat 'identity
+                      (append (list (less-css--maybe-shell-quote-command less-css-lessc-command))
+                              (mapcar 'shell-quote-argument less-css-lessc-options)
+                              (list (shell-quote-argument
+                                     (or less-css-input-file-name buffer-file-name))
+                                    (shell-quote-argument (less-css--output-path))))
+                      " "))
+        (add-hook 'compilation-finish-functions
+                  (lambda (buf msg)
+                    (unless (string-match-p "^finished" msg)
+                      (display-buffer buf)))
+                  nil
+                  t)))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Minor mode
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; TODO: interpolation ("@{val}"), escaped values (~"..."), JS eval (~`...`), custom faces
+(defconst less-css-font-lock-keywords
+  '(;; Variables
+    ("@[a-z_-][a-z-_0-9]*" . font-lock-constant-face)
+    ("&" . font-lock-preprocessor-face)
+    ;; Mixins
+    ("\\(?:[ \t{;]\\|^\\)\\(\\.[a-z_-][a-z-_0-9]*\\)[ \t]*;" . (1 font-lock-keyword-face)))
+  )
+
+;;;###autoload
+(define-derived-mode less-css-mode css-mode "LESS"
+  "Major mode for editing LESS files, http://lesscss.org/
+Special commands:
+\\{less-css-mode-map}"
+  (font-lock-add-keywords nil less-css-font-lock-keywords)
+  ;; cpp-style comments
+  (modify-syntax-entry ?/ ". 124b" less-css-mode-syntax-table)
+  (modify-syntax-entry ?* ". 23" less-css-mode-syntax-table)
+  (modify-syntax-entry ?\n "> b" less-css-mode-syntax-table)
+  ;; Special chars that sometimes come at the beginning of words.
+  (modify-syntax-entry ?. "'" less-css-mode-syntax-table)
+
+  (set (make-local-variable 'comment-start) "//")
+  (set (make-local-variable 'comment-end) "")
+  (set (make-local-variable 'indent-line-function) 'less-css-indent-line)
+  (when (functionp 'css-smie-rules)
+    (smie-setup css-smie-grammar #'css-smie-rules
+                :forward-token #'css-smie--forward-token
+                :backward-token #'css-smie--backward-token))
+
+  (add-hook 'after-save-hook 'less-css-compile-maybe nil t))
+
+(define-key less-css-mode-map "\C-c\C-c" 'less-css-compile)
+
+(defun less-css-indent-line ()
+  "Indent current line according to LESS CSS indentation rules."
+  (let ((css-navigation-syntax-table less-css-mode-syntax-table))
+    (if (fboundp 'css-indent-line)
+        (css-indent-line)
+      (smie-indent-line))))
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("\\.less\\'" . less-css-mode))
+
+
+(provide 'less-css-mode)
+;;; less-css-mode.el ends here