1 # Context Coloring [![Build Status](https://travis-ci.org/jacksonrayhamilton/context-coloring.png?branch=develop)](https://travis-ci.org/jacksonrayhamilton/context-coloring)
4 <img alt="Screenshot of JavaScript code highlighted by context." src="screenshot.png" title="Screenshot">
7 Highlights code according to function context.
9 - Code in the global scope is one color. Code in functions within the global
10 scope is a different color, and code within such functions is another color,
12 - Identifiers retain the color of the scope in which they are declared.
14 Lexical scope information at-a-glance can assist a programmer in understanding
15 the overall structure of a program. It can help to curb nasty bugs like name
16 shadowing. A rainbow can indicate excessive complexity. State change within a
17 closure is easily monitored.
19 By default, Context Coloring still highlights comments and strings
20 syntactically. It is still easy to differentiate code from non-code, and strings
21 cannot be confused for variables.
23 This coloring strategy is probably more useful than conventional syntax
24 highlighting. Highlighting keywords can help one to detect spelling errors, but
25 a [linter][] could also spot those errors, and if integrated with [flycheck][],
26 an extra spot opens up in your editing toolbelt.
28 Give context coloring a try; you may find that it *changes the way you write
33 - Supported languages: JavaScript
34 - Light and dark (customizable) color schemes.
35 - Very fast for files under 1000 lines.
41 JavaScript language support requires either [js2-mode][] or
42 [Node.js 0.10+][node], respectively.
44 - Clone this repository.
48 git clone https://github.com/jacksonrayhamilton/context-coloring.git
51 - Byte-compile the package for improved speed.
58 - Add the following to your `~/.emacs` file:
61 (add-to-list 'load-path "~/.emacs.d/context-coloring")
62 (require 'context-coloring)
63 (add-hook 'js-mode-hook 'context-coloring-mode)
68 You can adjust the colors to your liking using
69 `context-coloring-set-colors`. The first argument is an alist of levels, and the
70 optional second argument is the new total number of levels. This plugin does not
71 figure out the total for you; you need to specify it if your number of colors is
72 different from the default (`7`).
74 I like to take the colors from an existing theme and use those to create a
75 rainbow that matches that theme. The end result is consistent, and usually looks
76 as good as the theme does. Here's an example for `tango`:
81 (require 'context-coloring)
82 (defun jrh-context-coloring-tango ()
84 (context-coloring-set-colors
85 '((comment . "#5f615c")
86 (0 . "#2e3436") ; Globals.
93 (7 . "#8ae234") ; "You're screwed" colors.
100 (jrh-context-coloring-tango)
105 To add support for a new language, write a "scopifier" for it, and add an entry
106 to `context-coloring-dispatch-plist`. Then the plugin should handle the rest.
108 A "scopifier" is a CLI program that reads a buffer's contents from stdin and
109 writes a JSON array of numbers to stdout. Every three numbers in the array
110 represent a range of color. For instance, if I fed the following string of
111 JavaScript code to a scopifier,
114 var a = function () {};
117 then the scopifier would produce the following array:
123 Where, for every three numbers, the first number is a 1-indexed start [point][],
124 the second number is an exclusive end point, and the third number is a scope
125 level. The result of applying level 0 coloring to the range [1, 24) and then
126 applying level 1 coloring to the range [9, 23) would result in the following
130 <img alt="Screenshot of ranges [1, 24) and [9, 23)." src="scopifier.png" title="Screenshot">
133 If there is an abstract syntax tree generator for your language, you can walk
134 the syntax tree, find variables and scopes, and build their positions and levels
135 into an array like the one above.
137 [linter]: http://jshint.com/about/
138 [flycheck]: http://www.flycheck.org/
139 [point]: http://www.gnu.org/software/emacs/manual/html_node/elisp/Point.html
140 [js2-mode]: https://github.com/mooz/js2-mode
141 [node]: http://nodejs.org/download/
142 [load path]: https://www.gnu.org/software/emacs/manual/html_node/emacs/Lisp-Libraries.html