dir-locals.el: Adds White Space support

The White Space package, which is available since GNU Emacs 22, is
loaded and activated locally in prog-mode and cmake-mode.

Also, using White Space variables, we set highlighting through faces
on wrong indentation and the maximum length of a coding line.

Notice that:
 - The highlighting for the characters beyond the set length of a
   coding line is not activated by default, only for wrong
   indentations.
 - If the White Space package is not available, errors on loading or
   activation are ignored.
 - If the White Space mode is not activated the set variables would
   not have any effect.

v2: python-mode inherits from prog-mode
v3: Removed too long lines trail highlighting, as suggested by Ilia
    Mirkin.

Signed-off-by: Andres Gomez <agomez@igalia.com>
Acked-by: Ilia Mirkin <imirkin@alum.mit.edu>

1 files changed, 13 insertions, 4 deletions

diff --git a/.dir-locals.el b/.dir-locals.el
index 3bdca176b..2a37aaf44 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -1,11 +1,20 @@
 ((nil . ((indent-tabs-mode . t)
 	 (tab-width . 8)
-	 (show-trailing-whitespace . t)))
+	 (show-trailing-whitespace . t)
+	 (whitespace-style face indentation)
+	 (whitespace-line-column . 79)))
  (prog-mode .
-	    ((c-file-style . "linux")))
+	    ((c-file-style . "linux")
+	     (eval ignore-errors
+		   (require 'whitespace)
+		   (whitespace-mode 1))))
  (cmake-mode .
-	     ((cmake-tab-width . 8)))
+	     ((cmake-tab-width . 8)
+	      (eval ignore-errors
+		    (require 'whitespace)
+		    (whitespace-mode 1))))
  (python-mode .
 	      ((indent-tabs-mode . nil)
-	       (tab-width . 4)))
+	       (tab-width . 4)
+	       (whitespace-line-column . 80)))
  )