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