Emacs: highlighting TODO *only* in comments

Question

This question is related to another one, Emacs :TODO indicator at left side. I recently came across a minor mode I like a lot called FixmeMode. It supports auto highlighting

Answer 1

Maybe this will help: there's a fn c-in-literal in cc-mode, and a similar csharp-in-literal in csharp mode. The return value is c if in a C-style comment, c++ if in a C++ style comment. You could add that to the code at Emacs :TODO indicator at left side to get what you want.

(defun annotate-todo ()
   "put fringe marker on TODO: lines in the curent buffer"
  (interactive)
  (let (lit)
  (save-excursion
    (goto-char (point-min))
    (while (re-search-forward "TODO:" nil t)
      (progn
        (setq lit (c-in-literal)) ;; or csharp-in-literal
        (if (or (eq lit 'c) (eq lit 'c++))
            (let ((overlay (make-overlay (- (point) 5) (point))))
              (overlay-put overlay 'before-string
                           (propertize "A"
                                       'display
                                       '(left-fringe   ;; right
                                         horizontal-bar
                                         better-fringes-important-bitmap))))))))))