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15e08c6 Jun 13, 2010
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Hacking the ArashiJS code

Well, hello there! It's so nice to have you visit here. Please, do continue reading.

Directory structure

  • src contains all the JavaScript source code.
  • snd contains the WAV PCM conversions of the original sounds.
  • img contains the SVG and PNG conversions of the original images. (unused)
  • util contains some utilities used in conversion and by the Makefile.
  • dist contains distributables created by make.

Code structure

The game loop is found in src/engine.js. The engine basically keeps track of the game state, and calls the related handler method each frame. These methods in turn live in the source files underneath src/gamestates/.

All other files are basically utilities for getting things done:

  • The src/vakit/ directory contains drawing utilities (which stem from the VAKit library in the original Project ARASHI).

  • The src/soundkit.js library is a minimal abstraction for playing sound effects.

  • The src/random.js library contains a pseudo-random number generator. The most significant feature of this is that it is seedable. (This is necessary for playback of recordings.)

  • The src/grid.js library contains the code for reading and drawing the level's grid, and includes definitions for levels converted from the original.

Build infrastructure

A Makefile is included, which fulfills some optional development tasks:

  • make lint runs JSLint on all source files. Before each source file is processed, the file util/lint.head.js is concatenated. This file contains the default JSLint options used throughout the source code. You can override the environment variables RHINO and JSLINT if the defaults don't work for your set-up.

  • make dist creates the compressed JavaScript and CSS distributables under dist/. The file util/dist.head.js is concatenated to the input of the compressor. You can override the environment variables JAVA, YUICOMP, HTMLCOMP and OGGENC if the defaults don't work for your set-up.

  • make clean is your run-off-the-mill cleaning target for the above two.

Testing

There is no fancy automated testing, but it is quite easy to test individual game components during development.

A file testing.template.html is included, which is basically a commented start-up page. To use it, make a copy of it called testing.html. The copy won't be tracked by version control, so you may put together quick and dirty tests as you please.

The testing.template.html template also demonstrates how Engine.start can be supplied a different 'entry-point' object. This technique can be used to test a single drawing or animation, or perhaps simply to skip the intro and jump right into a specific level.

Canvas pecularities

The HTML5 canvas has a fair amount of state variables. This is the place to document the pecularities of how ArashiJS deals with these variables.

  • All draw* methods only ever draw paths. Other methods (usually called paint) will do an actual stroke or fill operation.

  • Always reset globalAlpha to 1.0 when you're done using it.

  • Always use stack methods (save and restore) and painting methods (beginPath and stroke or fill) in a block or hierarchy fashion. There should be no partial overlaps in their scope.

  • Indent the above like a block, too.

  • Set the stroke or fill parameters before starting a path.