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first time StackExchange user here.

I'm having trouble with highlight-chars (probably font-lock) and magit. Enabling hc-toggle-highlight-* functions will remove the coloring from magit buffers.

enter image description here

Possibly duplicate: Font-lock for strings messes up non-code buffers

Anyone else have this trouble, or know some possible workaround?

Minimum .emacs:

(require 'package)
(add-to-list 'package-archives
         '("melpa" . "https://melpa.org/packages/"))
(package-initialize)

(require 'magit) ;; Current version 20160210.555
(require 'highlight-chars) ;; Current version 20151231.1335

;; (hc-toggle-highlight-tabs t)
;; (hc-toggle-highlight-trailing-whitespace t)
(add-hook 'font-lock-mode-hook 'hc-highlight-tabs)
(add-hook 'font-lock-mode-hook 'hc-highlight-trailing-whitespace)
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  • I've seen this happen when enabling whitespace-mode in a magit buffer. Never got around to investigating further though.
    – npostavs
    Feb 11, 2016 at 14:39

1 Answer 1

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You might need to look at the Magit code to see what it is doing. You don't say what highlighting Magit does normally, and just what changes when highlight-chars.el (Highlight Library) is added to the mix. I don't use Magit -- maybe someone else can speak to this.

But highlight-chars.el does add to font-lock-keywords for things like highlighting tabs and trailing whitespace. It's possible that this interferes with the font-lock keywords used by Magit.

However, user option hc-font-lock-override controls whether the current highlighting face used by hc-* commands overrides (t), is overridden by (keep), or merges with (append or prepend) any existing highlighting.

You should thus be able to make hc-* highlighting cohabit well with other text-property highlighting - you can control which highlighting of a given piece of text, highlighting by hc-* or highlighting by some other code, has precedence, and how much it dominates the other highlighting.

E.g., you can set the value of hc-font-lock-override to keep (e.g., using M-x customize-option hc-font-lock-override), to prevent hc-* highlighting from overwriting any already existing highlighting.

See also options hc-other-chars and hc-other-chars-NOT, which control which chars are governed by hc-toggle-highlight-other-chars.

You might also try changing the order (i.e., when you turn on the hc-* highlighting). hc-highlight-trailing-whitespace and hc-highlight-tabs just add patterns to match at the end of font-lock-keywords.

However, be aware that highlighting from text properties (e.g. face or font-lock-face) always has less precedence than highlighting from overlays. Library highlight-chars.el uses text-property highlighting, as does all use of font-lock. If some other library uses overlay highlighting on the same text area then the overlay highlighting wins in case of conflict - always.

[2018-04-07: I updated highlight-chars.el to let option hc-font-lock-override (previously called hc-other-chars-font-lock-override) control all hc-* highlighting, not just other-char highlighting.]

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  • Good idea, but unfortunately it did not solve the problem. I started digging in the magit code, and especially the magit-section-make-overlay function. My newest hypothesis is that font-lock conflicts with overlay-put from the built in buffer.c.
    – Seba
    Feb 11, 2016 at 19:52
  • Overlay properties always override text properties. highlight-chars.el uses font-lock, which, yes, uses text properties. If Magit uses overlays then they should take precedence. If its overlays use property face then that face should be seen, not a face used by highlight-chars.el. But it sounds like you are seeing the opposite (you said that h-c breaks Magit, not the other way around).
    – Drew
    Feb 11, 2016 at 20:05
  • What makes you think that Magit is using overlays at the locations where h-c is trying to highlight? Glancing at some of the code, I see that the overlay is used for magit-section-highlight and magit-section-highlight-selection. What happens if you remove those from option magit-section-highlight-hook, as a test? That presumably will take overlays out of the equation.
    – Drew
    Feb 11, 2016 at 20:23

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