Color Identifiers Mode

Color Identifiers is a minor mode for Emacs that highlights each source code identifier uniquely based on its name. It is inspired by a post by Evan Brooks.

Currently it supports Scala (scala-mode2), JavaScript (js-mode and js2-mode), Ruby, Python, Emacs Lisp, Clojure, C, C++, Rust, Java, and Go. You can add support for your favorite mode by modifying color-identifiers:modes-alist and optionally calling color-identifiers:set-declaration-scan-fn.

Check out the demo.

It picks colors adaptively to fit the theme:

Use M-x color-identifiers:regenerate-colors after a theme change.

Installation

Color Identifiers is in MELPA. First set up MELPA:

(package-initialize)
(add-to-list 'package-archives
             '("melpa" . "https://melpa.org/packages/") t)
(package-refresh-contents)

Then install it:

(package-install 'color-identifiers-mode)

Finally, visit a supported file and type M-x color-identifiers-mode.

If you like it, enable it for all supported files by adding the following to your init file:

(add-hook 'after-init-hook 'global-color-identifiers-mode)

Configuration

• Recoloring delay: the time before recoloring newly appeared identifiers is 2 seconds by default. To change it e.g. to 1 second add to your config (setq color-identifiers:recoloring-delay 1)

• Additional face-properties (such as italic or bold) can be added to the identifiers by modifying color-identifiers:extra-face-attributes. E.g. to make identifiers look bold use (setq color-identifiers:extra-face-attributes '(:weight bold)). But make sure not to change :foreground because it is the color of identifiers.

• To make the variables stand out, you can turn off highlighting for all other keywords in supported modes using a code like:

  (defun myfunc-color-identifiers-mode-hook ()
    (let ((faces '(font-lock-comment-face font-lock-comment-delimiter-face font-lock-constant-face font-lock-type-face font-lock-function-name-face font-lock-variable-name-face font-lock-keyword-face font-lock-string-face font-lock-builtin-face font-lock-preprocessor-face font-lock-warning-face font-lock-doc-face font-lock-negation-char-face font-lock-regexp-grouping-construct font-lock-regexp-grouping-backslash)))
      (dolist (face faces)
        (face-remap-add-relative face '(:inherit default))))
    (face-remap-add-relative 'font-lock-keyword-face '((:weight bold)))
    (face-remap-add-relative 'font-lock-comment-face '((:slant italic)))
    (face-remap-add-relative 'font-lock-builtin-face '((:weight bold)))
    (face-remap-add-relative 'font-lock-preprocessor-face '((:weight bold)))
    (face-remap-add-relative 'font-lock-function-name-face '((:slant italic)))
    (face-remap-add-relative 'font-lock-string-face '((:slant italic)))
    (face-remap-add-relative 'font-lock-constant-face '((:weight bold))))
  (add-hook 'color-identifiers-mode-hook 'myfunc-color-identifiers-mode-hook)

  

Contributing

After having made changes to color-identifiers-mode.el you can test for regressions by running ninja tests. It checks lack of byte-compilation warnings and color-highlighting in various modes.

Improvements to the tests or the core mode are always welcome!