emacs highlight background changes

Question

hi: Each time I insert some text in emacs , it will highlight the newly added text. I wonder how to change the background color of the highlight, because the highlight background color is very close to the font color , as a result, I can hardly recognize the code that I am writing.

thank you soooo much

Answer 1

For issues with fonts (which Emacs calls faces) inside of Emacs, it is often helpfull to know the function 'list-faces-display'. You can call this with M-x and it will list all faces defined in the current frame. This can be helpfull both identifying which face is problematic, it will also give you its name which can be used to modify the face. For instance to change the foreground colour of the face named "button" you can call something like this:

(set-face-foreground 'button "cyan")

The effect will be immediately visible. Many aspects of faces can be changed, including colour, font familiy and font size.

Obviously, this will not help you if the problematic behaviour stems from the terminal emulator you are using, as it would appear from some of the comments to your question, then the problem is outside of Emacs and cannot be fixed from inside of Emacs. Even so, knowing about 'list-faces-display' is usefull.

Answer 2

I had this exact question and managed to solve it using the following ways. But I also had another thing in mind: a marker to show which lines are modified.

For tracking changes between the saved file and the buffer, we should use the highlight-changes-mode. But before enabling that mode, we need to prepare some stuff as explained beautifully here for the line marks:

  ;; a part to add the fringe marks to the gutter. To change the shape, read the explanation of it in this code.
  (eval-after-load "hilit-chg"
        '(progn
           (defvar highlight-fringe-mark 'filled-square
             "The fringe bitmap name marked at changed line.
       Should be selected from `fringe-bitmaps'.")

           (defadvice hilit-chg-make-ov (after hilit-chg-add-fringe activate)
             (mapc (lambda (ov)
                 (if (overlay-get ov 'hilit-chg)
                 (let ((fringe-anchor (make-string 1 ?x)))
                   (put-text-property 0 1 'display
                          (list 'left-fringe highlight-fringe-mark)
                          fringe-anchor)
                   (overlay-put ov 'before-string fringe-anchor))
               ))
                   (overlays-at (ad-get-arg 1))))))
  
  ;; make the highlight-changes-mode reset when the file is saved
  (add-hook 'local-write-file-hooks 'highlight-changes-rotate-faces)
  (add-hook 'after-save-hook
              (lambda ()
                (when highlight-changes-mode
                  (save-restriction
                    (widen)
                    (highlight-changes-remove-highlight (point-min) (point-max))))))

make sure it is enabled globally except for buffers that start with ' and *

  (setq highlight-changes-global-modes t)
  (global-highlight-changes-mode)

make the mode to respect the syntax-highlighting

  ;; find the name of other faced using M-x ~list-faces-display~
  (custom-set-faces
    '(highlight-changes ((t (:background "dark green" :foreground nil)))))
  (set-face-foreground 'highlight-changes nil)
  (set-face-background 'highlight-changes "dark green")