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 ## Installation
  38
  39 Requires Emacs 24+.
  40
  41 JavaScript language support requires either [js2-mode][] or
  42 [Node.js 0.10+][node], respectively.
  43
  44 ### ELPA
  45
  46 - `M-x package-refresh-contents RET`
  47 - `M-x package-install RET context-coloring RET`
  48
  49 ### Git
  50
  51 - Clone this repository.
  52
  53 ```bash
  54 cd ~/.emacs.d/
  55 git clone https://github.com/jacksonrayhamilton/context-coloring.git
  56 ```
  57
  58 - Byte-compile the package for improved speed.
  59
  60 ```bash
  61 cd context-coloring/
  62 make compile
  63 ```
  64
  65 - Add the following to your `~/.emacs` file:
  66
  67 ```lisp
  68 (add-to-list 'load-path "~/.emacs.d/context-coloring")
  69 (require 'context-coloring)
  70 (add-hook 'js-mode-hook 'context-coloring-mode)
  71 ```
  72
  73 ## Customizing
  74
  75 Built-in themes are accessible via `context-coloring-load-theme`.  Available
  76 themes are: `monokai`, `solarized`, `tango` and `zenburn`.
  77
  78 ```lisp
  79 (require 'context-coloring)
  80 (context-coloring-load-theme 'zenburn)
  81 ```
  82
  83 You can define your own themes, too:
  84
  85 ```lisp
  86 (context-coloring-define-theme
  87  'zenburn
  88  :colors '("#DCDCCC"
  89            "#93E0E3"
  90            "#BFEBBF"
  91            "#F0DFAF"
  92            "#DFAF8F"
  93            "#CC9393"
  94            "#DC8CC3"
  95            "#94BFF3"
  96            "#9FC59F"
  97            "#D0BF8F"
  98            "#DCA3A3"))
  99 ```
 100
 101 ## Extending
 102
 103 To add support for a new language, write a "scopifier" for it, and define a new
 104 coloring dispatch strategy with `context-coloring-define-dispatch`. Then the
 105 plugin should handle the rest.
 106
 107 A "scopifier" is a CLI program that reads a buffer's contents from stdin and
 108 writes a JSON array of numbers to stdout. Every three numbers in the array
 109 represent a range of color. For instance, if I fed the following string of
 110 JavaScript code to a scopifier,
 111
 112 ```js
 113 var a = function () {};
 114 ```
 115
 116 then the scopifier would produce the following array:
 117
 118 ```js
 119 [1,24,0,9,23,1]
 120 ```
 121
 122 Where, for every three numbers, the first number is a 1-indexed start [point][],
 123 the second number is an exclusive end point, and the third number is a scope
 124 level. The result of applying level 0 coloring to the range &#91;1, 24) and then
 125 applying level 1 coloring to the range &#91;9, 23) would result in the following
 126 coloring:
 127
 128 <p align="center">
 129   <img alt="Screenshot of ranges &#91;1, 24) and &#91;9, 23)." src="scopifier.png" title="Screenshot">
 130 </p>
 131
 132 If there is an abstract syntax tree generator for your language, you can walk
 133 the syntax tree, find variables and scopes, and build their positions and levels
 134 into an array like the one above.
 135
 136 For example, a Ruby scopifier might be defined and implemented like this:
 137
 138 ```lisp
 139 (context-coloring-define-dispatch
 140  'ruby
 141  :modes '(ruby-mode)
 142  :executable "ruby"
 143  :command "/home/username/scopifier")
 144 ```
 145
 146 ```ruby
 147 #!/usr/bin/env ruby
 148 def scopifier(code)
 149     # Parse code.
 150     # Return an array.
 151 end
 152 print scopifier ARGF.read
 153 ```
 154
 155 [linter]: http://jshint.com/about/
 156 [flycheck]: http://www.flycheck.org/
 157 [zenburn]: http://github.com/bbatsov/zenburn-emacs
 158 [point]: http://www.gnu.org/software/emacs/manual/html_node/elisp/Point.html
 159 [js2-mode]: https://github.com/mooz/js2-mode
 160 [node]: http://nodejs.org/download/
 161 [load path]: https://www.gnu.org/software/emacs/manual/html_node/emacs/Lisp-Libraries.html