On Mon, Jun 22, 2015 at 3:13 AM, Stefan Monnier 
<monnier@iro.umontreal.ca> wrote:
> There's also a real problem: how should we treat url(foo)bar) ?

I find the regexp 
"url\\((\\)[[:space:]]*[^\"'\n[:space:]]+[[:space:]]*\\()\\)"
hungry enough to work for all of the following cases:

url(foobar);
url(foo)bar);
url(http://www.example.com/foo.html);
url('http://www.example.com/foo.html');
url("http://www.example.com/foo.html");

> Just like single quotes and double quotes are usually highlighted as
> part of the string.  IOW, I think it's OK to highlight the parens as
> part of the string, tho only when the argument inside the parens is 
> not
> itself wrapped in '...' or "...".
> 
> So we should use a regexp that only matches when the contents of the
> parens is not quoted.
> 
> If you really care about it you could add a font-lock-keyword which
> matches "url(...)" and overrides the face on the open and close 
> parens.

Thanks for the tip, I'll do that.

In sum, the patch now looks like:


 From 67e48674bf42faa20ee8571ecf84c4bdc48148a3 Mon Sep 17 00:00:00 2001
 From: =?UTF-8?q?Simen=20Heggest=C3=B8yl?= <simenheg@gmail.com>
Date: Sat, 20 Jun 2015 17:17:31 +0200
Subject: [PATCH] Handle comments inside unquoted URIs in css-mode

* lisp/textmodes/css-mode.el (css--uri-re): New defconst.
(css-syntax-propertize-function): New function.
(css-mode): Set `syntax-propertize-function'.
---
 lisp/textmodes/css-mode.el | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/lisp/textmodes/css-mode.el b/lisp/textmodes/css-mode.el
index 424cdb7..1383420 100644
--- a/lisp/textmodes/css-mode.el
+++ b/lisp/textmodes/css-mode.el
@@ -198,6 +198,14 @@
     (modify-syntax-entry ?- "_" st)
     st))

+(eval-and-compile
+ (defconst css--uri-re
+ "url\\((\\)[[:space:]]*[^\"'\n[:space:]]+[[:space:]]*\\()\\)"))
+
+(defconst css-syntax-propertize-function
+ (syntax-propertize-rules
+ (css--uri-re (1 "|") (2 "|"))))
+
 (defconst css-escapes-re
   "\\\\\\(?:[^\000-\037\177]\\|[0-9a-fA-F]+[ \n\t\r\f]?\\)")
 (defconst css-nmchar-re (concat "\\(?:[-[:alnum:]]\\|" css-escapes-re 
"\\)"))
@@ -278,7 +286,13 @@
               "\\(?:\\(" css-proprietary-nmstart-re "\\)\\|"
               css-nmstart-re "\\)" css-nmchar-re "*"
               "\\)\\s-*:")
- (1 (if (match-end 2) 'css-proprietary-property 'css-property)))))
+ (1 (if (match-end 2) 'css-proprietary-property 'css-property)))
+ ;; Make sure the parens in a url(...) expression receive the
+ ;; default face. This is done because the parens may sometimes
+ ;; receive generic string delimiter syntax (see
+ ;; `css-syntax-propertize-function').
+ (,css--uri-re
+ (1 'default t) (2 'default t))))

 (defvar css-font-lock-keywords (css--font-lock-keywords))

@@ -381,6 +395,8 @@ pseudo-classes, and at-rules."
   (setq-local comment-start-skip "/\\*+[ \t]*")
   (setq-local comment-end "*/")
   (setq-local comment-end-skip "[ \t]*\\*+/")
+ (setq-local syntax-propertize-function
+ css-syntax-propertize-function)
   (setq-local fill-paragraph-function #'css-fill-paragraph)
   (setq-local adaptive-fill-function #'css-adaptive-fill)
   (setq-local add-log-current-defun-function #'css-current-defun-name)
-- 
2.5.0