Font Lock mode can highlight using any face, but Emacs defines several faces specifically for Font Lock to use to highlight text. These Font Lock faces are listed below. They can also be used by major modes for syntactic highlighting outside of Font Lock mode (see Major Mode Conventions).
Each of these symbols is both a face name, and a variable whose default value is the symbol itself. Thus, the default value of font-lock-comment-face is font-lock-comment-face.
The faces are listed with descriptions of their typical usage, and in order of greater to lesser prominence. If a mode’s syntactic categories do not fit well with the usage descriptions, the faces can be assigned using the ordering as a guide.
font-lock-warning-facefor a construct that is peculiar (e.g., an unescaped confusable quote in an Emacs Lisp symbol like ‘‘foo’), or that greatly changes the meaning of other text, like ‘;;;###autoload’ in Emacs Lisp and ‘#error’ in C.
font-lock-function-name-facefor the name of a function being defined or declared.
font-lock-variable-name-facefor the name of a variable being defined or declared.
font-lock-keyword-facefor a keyword with special syntactic significance, like ‘for’ and ‘if’ in C.
font-lock-comment-facefor comments.
font-lock-comment-delimiter-facefor comments delimiters, like ‘/*’ and ‘*/’ in C. On most terminals, this inherits from font-lock-comment-face.
font-lock-type-facefor the names of user-defined data types.
font-lock-constant-facefor the names of constants, like ‘NULL’ in C.
font-lock-builtin-facefor the names of built-in functions.
font-lock-preprocessor-facefor preprocessor commands. This inherits, by default, from font-lock-builtin-face.
font-lock-string-facefor string constants.
font-lock-doc-facefor documentation embedded in program code inside specially-formed comments or strings. This face inherits, by default, from font-lock-string-face.
font-lock-doc-markup-facefor mark-up elements in text using font-lock-doc-face. It is typically used for the mark-up constructs in documentation embedded in program code, following conventions such as Haddock, Javadoc or Doxygen. This face inherits, by default, from font-lock-constant-face.
font-lock-negation-char-facefor easily-overlooked negation characters.
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Licensed under the GNU GPL license.
https://www.gnu.org/software/emacs/manual/html_node/elisp/Faces-for-Font-Lock.html