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The thing I want to do is to highlight regions in a file covered by jest JavaScript tests. For testing I'm in an .emacs buffer, and I'm trying to highlight a single line in another buffer that I have opened in a different window.

I was looking at this question, which uses hlt-highlight-region from library Highlight, but I'm not able to make this work.

I have code like this that should change the single line's background to green:

  (let* ((dir "/home/kuba/projects/jcubic/terminal/repo")
         (buffer (get-file-buffer (concat dir "/js/jquery.terminal-src.js")))
         (start '((line . 3156) (column . 0)))
         (end '((line . 3156) (column . 18))))
    (with-current-buffer buffer
      (let* ((start-line-pos (line-beginning-position (cdr (assoc 'line start))))
             (start-pos (+ start-line-pos (cdr (assoc 'column start))))
             (end-line-pos (line-beginning-position (cdr (assoc 'line end))))
             (end-pos (+ end-line-pos (cdr (assoc 'column end)))))
        (hlt-highlight-region start-pos end-pos '((t (:background "green")))))))

But the code is returning nil and nothing happens. What's wrong with this code?

  • Your problem is not (hlt-highlight-region N1 N2 '((t (:background "green"))), at least. If you just do that, with two buffer positions for N1 and N2 then you'll see that it works. Try inserting (message "START: %S, END: %S" start-pos end-pos) just before the call to hlt-highlight-region, to see what values those vars have. Or use M-x debug-on-entry followed by the name of your function, and walk through the debugger with d or c to see what happens. – Drew Jun 17 '18 at 0:34
  • @Drew I've investigated and it seems that line-begninning-position is not accepting line number as argument maybe it's offset or something. – jcubic Jun 17 '18 at 7:00
  • line-beginning-position accepts a number of lines to move. It returns the buffer position of the beginning of the line that it arrives at after that move. (The move is temporary/simulated - point is left where it was initially.) If you want the position of the beginning of the current line then don't pass an argument. – Drew Jun 17 '18 at 14:42

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