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 were declared.
  13 - Comments are a neutral color.
  14
  15 Lexical scope information at-a-glance can assist a programmer in understanding
  16 the overall structure of a program. It can also help curb nasty bugs like name
  17 shadowing or unexpected assignment. A rainbow can indicate excessive
  18 complexity. A spot of contrast followed by an assignment expression could be a
  19 side-effect. The state of a closure could be undergoing change.
  20
  21 This coloring strategy is probably more useful than conventional *syntax*
  22 highlighting. Highlighting keywords can help one to detect spelling errors, and
  23 highlighting the content between quotation marks can alert one to unclosed
  24 string literals. But a [linter][] could also spot those errors, and if
  25 integrated via [flycheck][], an extra spot opens up in your editing toolbelt.
  26
  27 Give context coloring a try; you may find that it *changes the way you write
  28 code*.
  29
  30 ## Features
  31
  32 - Supported languages: JavaScript
  33 - Light and dark (customizable) color schemes.
  34 - Insanely fast for regular files, quick for big ones too.
  35   - jQuery (9191 lines): 0.20 seconds (js2-mode), 0.57 seconds (js-mode)
  36   - Lodash (6786 lines): 0.07 seconds (js2-mode), 0.35 seconds (js-mode)
  37   - Async (1124 lines): 0.03 seconds (js2-mode), 0.17 seconds (js-mode)
  38   - mkdirp (98 lines): 0.002 seconds (js2-mode), 0.09 seconds (js-mode)
  39
  40 \* js2-mode parses idly, irrespective of this plugin; its benchmarks represent
  41 coloring only. js-mode benchmarks represent parsing and coloring.
  42
  43 ## Usage
  44
  45 Requires Emacs 24+.
  46
  47 JavaScript language support requires either [js2-mode][] or
  48 [Node.js 0.10+][node], respectively.
  49
  50 - Clone this repository.
  51
  52 ```bash
  53 cd ~/.emacs.d/
  54 git clone https://github.com/jacksonrayhamilton/context-coloring.git
  55 ```
  56
  57 - Byte-compile the package for improved speed.
  58
  59 ```bash
  60 cd context-coloring/
  61 make compile
  62 ```
  63
  64 - Add the following to your `~/.emacs` file:
  65
  66 ```lisp
  67 (add-to-list 'load-path "~/.emacs.d/context-coloring")
  68 (require 'context-coloring)
  69 (add-hook 'js-mode-hook 'context-coloring-mode)
  70 ```
  71
  72 ## Customizing
  73
  74 You can adjust the colors to your liking using
  75 `context-coloring-set-colors`. The first argument is an alist of levels, and the
  76 optional second argument is the new total number of levels. This plugin does not
  77 figure out the total for you; you need to specify it if your number of colors is
  78 different from the default (`7`).
  79
  80 I like to take the colors from an existing theme and use those to create a
  81 rainbow that matches that theme. The end result is consistent, and usually looks
  82 as good as the theme does. Here's an example for `tango`:
  83
  84 ```lisp
  85 ;; ~/.emacs
  86 (load-theme 'tango)
  87 (require 'context-coloring)
  88 (defun jrh-context-coloring-tango ()
  89   (interactive)
  90   (context-coloring-set-colors
  91    '((comment . "#5f615c")
  92      (0       . "#2e3436") ; Globals.
  93      (1       . "#346604")
  94      (2       . "#204a87")
  95      (3       . "#5c3566")
  96      (4       . "#a40000")
  97      (5       . "#b35000")
  98      (6       . "#c4a000")
  99      (7       . "#8ae234") ; "You're screwed" colors.
 100      (8       . "#8cc4ff")
 101      (9       . "#ad7fa8")
 102      (10      . "#ef2929")
 103      (11      . "#fcaf3e")
 104      (12      . "#fce94f"))
 105    13))
 106 (jrh-context-coloring-tango)
 107 ```
 108
 109 ## Extending
 110
 111 To add support for a new language, write a "scopifier" for it, and add an entry
 112 to `context-coloring-dispatch-plist`. Then the plugin should handle the rest.
 113
 114 A "scopifier" is a CLI program that reads a buffer's contents from stdin and
 115 writes a JSON array of numbers to stdout. Every three numbers in the array
 116 represent a range of color. For instance, if I fed the following string of
 117 JavaScript code to a scopifier,
 118
 119 ```js
 120 var a = function () {};
 121 ```
 122
 123 then the scopifier would produce the following array:
 124
 125 ```js
 126 [1,24,0,9,23,1]
 127 ```
 128
 129 Where, for every three numbers, the first number is a 1-indexed start [point][],
 130 the second number is an exclusive end point, and the third number is a scope
 131 level. The result of applying level 0 coloring to the range &#91;1, 24) and then
 132 applying level 1 coloring to the range &#91;9, 23) would result in the following
 133 coloring:
 134
 135 <p align="center">
 136   <img alt="Screenshot of ranges &#91;1, 24) and &#91;9, 23)." src="scopifier.png" title="Screenshot">
 137 </p>
 138
 139 If there is an abstract syntax tree generator for your language, you can walk
 140 the syntax tree, find variables and scopes, and build their positions and levels
 141 into an array like the one above.
 142
 143 [linter]: http://jshint.com/about/
 144 [flycheck]: http://www.flycheck.org/
 145 [point]: http://www.gnu.org/software/emacs/manual/html_node/elisp/Point.html
 146 [js2-mode]: https://github.com/mooz/js2-mode
 147 [node]: http://nodejs.org/download/
 148 [load path]: https://www.gnu.org/software/emacs/manual/html_node/emacs/Lisp-Libraries.html