font-lock not working with my custom face

Question

I defined a custom face

(defface my-face '((t . (:background "green"))) "text")

that I want to use for font-lock syntax highlighting.

(defvar my-font-lock-keywords
 `(
   ("^\\*.*\\|;.*" . font-lock-comment-face)
   ("'[^']*'" . font-lock-string-face)
   ( ,(regexp-opt my-keywords 'symbols) . font-lock-keyword-face)
   ( ,(regexp-opt my-specials 'symbols) . my-face)
   (">[0-9A-F]+\\>\\|\\<[0-9]+\\>" . font-lock-constant-face)
))

The entire thing works fine if I replace my-face with font-lock-doc-face or similar, but loading my mode with this definition yields the error message

Error during redisplay: (jit-lock-function 1) signaled (void-variable my-face)

What is wrong with my face and the font-lock definition? Note that describe-face knows my-face and correctly shows its defined properties.

Answer 1

The "face" field is evaluted by font-lock. Hence, you need to quote the name of the face:

("^\\*.*\\|;.*" . 'font-lock-comment-face)

Note: Some standard faces like font-lock-keyword-face have variables with the same name as the face, whose value is the name of the face. This allows you to use those standard faces without a quote. However, this practice is deprecated.

Note 2: You can utilise the fact that the field is evaluated, e.g. by mapping a regexp to different faces depending on what is matched.

Note 3: Typically, strings and comments are not highlighted using font-lock keywords. Instead, they are highlighted according to the syntax table of the major mode.