I'm trying to create my own major mode. So far I've been able to set all the syntax highlighting that I need, but I'm struggling with this one.

Basically I need to color any word before an equal sign. Like this:

< action name="set_button">

Like the face nxml-attribute-local-name in nxml-mode.

To do this I'm using a regular expression to find that word and then set font-lock-variable-name-face.

I've tried the following regular expressions, but they didn't work. I don't know if it's because I'm not escaping them correctly or because emacs doesn't support them.

 ("\\(\w+\\)\\(?=\s*=\\)" . font-lock-variable-name-face)
 ("\b\\(\w+\\)\b=" . font-lock-variable-name-face)

There is nothing wrong with the elisp code. When I try a more simple regex it works.

Any ideas?


  • Technically, your second regexp should've worked. Even simpler: "\\w+=" would have worked (but it would also capture the equals sign. Your first regexp doesn't work because Emacs regexp doesn't implement non-capturing groups, other than that, it's fine.
    – wvxvw
    Commented Feb 23, 2015 at 15:13

1 Answer 1


After lots of trial and error I discovered what was wrong. I just needed to escape twice the 'w' letter Here is the final line:

 ("\\b\\(\\w+\\)\\b=" . font-lock-variable-name-face)

Looks easy now :-)

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