code.delx.au - gnu-emacs-elpa/blob - README.md

   1 # Context Coloring [![Build Status](https://travis-ci.org/jacksonrayhamilton/context-coloring.png?branch=develop)](https://travis-ci.org/jacksonrayhamilton/context-coloring)
   2
   3 <p align="center">
   4   <img alt="Screenshot of JavaScript code highlighted by context." src="screenshot.png" title="Screenshot">
   5 </p>
   6
   7 Highlights code according to function context.
   8
   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,
  11   and so on.
  12 - Identifiers retain the color of the scope in which they are declared.
  13
  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.
  18
  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.
  22
  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.
  27
  28 Give context coloring a try; you may find that it *changes the way you write
  29 code*.
  30
  31 ## Features
  32
  33 - Supported languages: JavaScript
  34 - Light and dark (customizable) color schemes.
  35 - Very fast for files under 1000 lines.
  36
  37 ## Usage
  38
  39 Requires Emacs 24+.
  40
  41 JavaScript language support requires either [js2-mode][] or
  42 [Node.js 0.10+][node], respectively.
  43
  44 - Clone this repository.
  45
  46 ```bash
  47 cd ~/.emacs.d/
  48 git clone https://github.com/jacksonrayhamilton/context-coloring.git
  49 ```
  50
  51 - Byte-compile the package for improved speed.
  52
  53 ```bash
  54 cd context-coloring/
  55 make compile
  56 ```
  57
  58 - Add the following to your `~/.emacs` file:
  59
  60 ```lisp
  61 (add-to-list 'load-path "~/.emacs.d/context-coloring")
  62 (require 'context-coloring)
  63 (add-hook 'js-mode-hook 'context-coloring-mode)
  64 ```
  65
  66 ## Customizing
  67
  68 You can adjust the colors to your liking using `context-coloring-set-colors`.
  69
  70 I like to take the colors from an existing theme and use those to create a
  71 rainbow that matches that theme. Here's an example for [`zenburn`][zenburn] (which is the
  72 theme used in the screenshot above).
  73
  74 ```lisp
  75 ;; ~/.emacs
  76 (load-theme 'zenburn t)
  77 (require 'context-coloring)
  78 (context-coloring-set-colors
  79  "#DCDCCC"
  80  "#93E0E3"
  81  "#BFEBBF"
  82  "#F0DFAF"
  83  "#DFAF8F"
  84  "#CC9393"
  85  "#DC8CC3"
  86  "#94BFF3"
  87  "#9FC59F"
  88  "#D0BF8F"
  89  "#DCA3A3")
  90 ```
  91
  92 ## Extending
  93
  94 To add support for a new language, write a "scopifier" for it, and define a new
  95 coloring dispatch strategy with `context-coloring-define-dispatch`. Then the
  96 plugin should handle the rest.
  97
  98 A "scopifier" is a CLI program that reads a buffer's contents from stdin and
  99 writes a JSON array of numbers to stdout. Every three numbers in the array
 100 represent a range of color. For instance, if I fed the following string of
 101 JavaScript code to a scopifier,
 102
 103 ```js
 104 var a = function () {};
 105 ```
 106
 107 then the scopifier would produce the following array:
 108
 109 ```js
 110 [1,24,0,9,23,1]
 111 ```
 112
 113 Where, for every three numbers, the first number is a 1-indexed start [point][],
 114 the second number is an exclusive end point, and the third number is a scope
 115 level. The result of applying level 0 coloring to the range &#91;1, 24) and then
 116 applying level 1 coloring to the range &#91;9, 23) would result in the following
 117 coloring:
 118
 119 <p align="center">
 120   <img alt="Screenshot of ranges &#91;1, 24) and &#91;9, 23)." src="scopifier.png" title="Screenshot">
 121 </p>
 122
 123 If there is an abstract syntax tree generator for your language, you can walk
 124 the syntax tree, find variables and scopes, and build their positions and levels
 125 into an array like the one above.
 126
 127 For example, a Ruby scopifier might be defined and implemented like this:
 128
 129 ```lisp
 130 (context-coloring-define-dispatch 'ruby
 131   :modes '(ruby-mode)
 132   :executable "ruby"
 133   :command "/home/username/scopifier")
 134 ```
 135
 136 ```ruby
 137 #!/usr/bin/env ruby
 138 def scopifier(code)
 139     # Parse code.
 140     # Return an array.
 141 end
 142 print scopifier ARGF.read
 143 ```
 144
 145 [linter]: http://jshint.com/about/
 146 [flycheck]: http://www.flycheck.org/
 147 [zenburn]: http://github.com/bbatsov/zenburn-emacs
 148 [point]: http://www.gnu.org/software/emacs/manual/html_node/elisp/Point.html
 149 [js2-mode]: https://github.com/mooz/js2-mode
 150 [node]: http://nodejs.org/download/
 151 [load path]: https://www.gnu.org/software/emacs/manual/html_node/emacs/Lisp-Libraries.html