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] and the [scopifier][] executable.
  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 ```
  71
  72 ### scopifier (for non-js2-mode users)
  73
  74 ```bash
  75 npm install -g scopifier
  76 ```
  77
  78 ## Usage
  79
  80 Add the following to your `~/.emacs` file:
  81
  82 ```lisp
  83 ;; non-js2-mode users:
  84 (add-hook 'js-mode-hook 'context-coloring-mode)
  85
  86 ;; js2-mode users:
  87 (add-to-list 'auto-mode-alist '("\\.js\\'" . js2-mode))
  88 (add-hook 'js2-mode-hook 'context-coloring-mode)
  89 ```
  90
  91 ## Customizing
  92
  93 Built-in themes are accessible via `context-coloring-load-theme`.  Available
  94 themes are: `monokai`, `solarized`, `tango` and `zenburn`.
  95
  96 ```lisp
  97 (require 'context-coloring)
  98 (context-coloring-load-theme 'zenburn)
  99 ```
 100
 101 You can define your own themes, too:
 102
 103 ```lisp
 104 (context-coloring-define-theme
 105  'zenburn
 106  :colors '("#DCDCCC"
 107            "#93E0E3"
 108            "#BFEBBF"
 109            "#F0DFAF"
 110            "#DFAF8F"
 111            "#CC9393"
 112            "#DC8CC3"
 113            "#94BFF3"
 114            "#9FC59F"
 115            "#D0BF8F"
 116            "#DCA3A3"))
 117 ```
 118
 119 ## Extending
 120
 121 To add support for a new language, write a "scopifier" for it, and define a new
 122 coloring dispatch strategy with `context-coloring-define-dispatch`. Then the
 123 plugin should handle the rest.
 124
 125 A "scopifier" is a CLI program that reads a buffer's contents from stdin and
 126 writes a JSON array of numbers to stdout. Every three numbers in the array
 127 represent a range of color. For instance, if I fed the following string of
 128 JavaScript code to a scopifier,
 129
 130 ```js
 131 var a = function () {};
 132 ```
 133
 134 then the scopifier would produce the following array:
 135
 136 ```js
 137 [1,24,0,9,23,1]
 138 ```
 139
 140 Where, for every three numbers, the first number is a 1-indexed start [point][],
 141 the second number is an exclusive end point, and the third number is a scope
 142 level. The result of applying level 0 coloring to the range &#91;1, 24) and then
 143 applying level 1 coloring to the range &#91;9, 23) would result in the following
 144 coloring:
 145
 146 <p align="center">
 147   <img alt="Screenshot of ranges &#91;1, 24) and &#91;9, 23)." src="scopifier.png" title="Screenshot">
 148 </p>
 149
 150 If there is an abstract syntax tree generator for your language, you can walk
 151 the syntax tree, find variables and scopes, and build their positions and levels
 152 into an array like the one above.
 153
 154 For example, a Ruby scopifier might be defined and implemented like this:
 155
 156 ```lisp
 157 (context-coloring-define-dispatch
 158  'ruby
 159  :modes '(ruby-mode)
 160  :executable "ruby"
 161  :command "/home/username/scopifier")
 162 ```
 163
 164 ```ruby
 165 #!/usr/bin/env ruby
 166 def scopifier(code)
 167     # Parse code.
 168     # Return an array.
 169 end
 170 print scopifier ARGF.read
 171 ```
 172
 173 When a `--version` argument is passed, a scopifier should print its version
 174 number and exit. For installable scopifiers, this allows context-coloring to
 175 check for updates as needed.
 176
 177 [linter]: http://jshint.com/about/
 178 [flycheck]: http://www.flycheck.org/
 179 [zenburn]: http://github.com/bbatsov/zenburn-emacs
 180 [point]: http://www.gnu.org/software/emacs/manual/html_node/elisp/Point.html
 181 [js2-mode]: https://github.com/mooz/js2-mode
 182 [node]: http://nodejs.org/download/
 183 [scopifier]: https://github.com/jacksonrayhamilton/scopifier
 184 [load path]: https://www.gnu.org/software/emacs/manual/html_node/emacs/Lisp-Libraries.html