tileset.coffee

#
# Choro - Tileset
# Copyright (c) 2012 Nico Hämäläinen <nico@bender.fi>
# MIT Licensed
#

#
# Events:
# - tilesetImageLoaded
#   This event is emitted when the initial tileset graphic is loaded
#   and saved into the tileset instance.
#

# Load needed modules
EventEmitter = require('events').EventEmitter
Canvas       = require 'canvas'
Util         = require '../util'
Rectangle    = Util.math.Rectangle

# Create a new Tileset with given attributes
Tileset = (@image, @tilesWide, @tilesHigh, @tileWidth, @tileHeight) ->
  # Make our tileset support events
  EventEmitter.call(this)

  # If image param isn't an image
  if not (@image instanceof Canvas.Image)
    throw new Tileset.Error(100)

  # If we're given silly sizes
  if @tilesWide <= 0 or @tilesHigh <= 0
    throw new Tileset.Error(101)
  if @tileWidth <= 0 or @tileHeight <= 0
    throw new Tileset.Error(102)

  # If our image size doesn't match tile dimension and count
  realWidth  = @tilesWide * @tileWidth
  realHeight = @tilesHigh * @tileHeight
  if @image.width < realWidth
    throw new Tileset.Error(103)

  # Rectangle -data of all the tiles
  @tileRectangles = []

  # Total count of tiles
  tileCount = @tilesWide * @tilesHigh

  # Create tile rectangles for the whole tileset
  tileIndex = 0
  # Loop through the rows of the tileset
  y = 0
  while y < @tilesHigh
    # Loop through the columns of the current row
    x = 0
    while x < @tilesWide
      # Create a rectangle object for this tile position
      @tileRectangles[tileIndex] = new Rectangle(
        x * @tileWidth,
        y * @tileHeight,
        @tileWidth,
        @tileHeight
      )
      tileIndex++
      x++
    y++

  this

# Set up event emitter
Tileset.prototype = EventEmitter.prototype

# Load the tileset image from a URL and save it into the instance
# emit an event to inform listeners of the image being succesfully
# loaded into the Tileset.
Tileset.prototype.loadImageFromURL = (imageURL) ->
  # Create the image object
  image = new Canvas.Image
  image.onload = () =>
    @image = image
    # Inform our listeners of this happening
    @emit('tilesetImageLoaded', image)
  image.src = imageURL

# Implement Tileset.Error
Tileset.Error = Util.implementErrorClass('TilesetError', {
  100: "Tileset image is not a valid Image or Canvas.Image object",
  101: "Tileset width and height must be more than zero",
  102: "Tileset tile sizes must be more than zero",
  103: "Space required by tiles is larger than given image"
})

# Exports
module.exports = Tileset