parallax.rb

$gtk.reset

require 'lib/window.rb'

class Parallax
  def self.set_args args
    @args = args
  end

  # singleton pattern
  def self.create *args
    @instance ||= self.new *args
    self
  end

  def self.checkInput
    @direction ||= 1

    if @args.inputs.keyboard.key_down.left
      @direction = -1
    elsif @args.inputs.keyboard.key_down.right
      @direction = 1
    elsif @args.inputs.keyboard.key_down.space && !@direction.zero?
      # save direction and stop
      @old_direction = @direction
      @direction = 0
    elsif @args.inputs.keyboard.key_down.space
      # restore saved direction
      @direction = @old_direction
    end
    @direction
  end

  def self.update
    @instance.update checkInput
    self
  end

  def self.render_into win
    @instance.render_into win
    self
  end

  def initialize w: 1280, h: 720, layers: [], speed: 1.2, direction: 1
    @w = w
    @h = h
    @layers = layers
    @speed = speed
    @direction = direction
    @sprites = []
    @xs = []
    layers.count.times do |i|
      @xs << 0
      3.times do
        @sprites << {x: 0, y: 0, w: @w, h: @h, path: layers[i]}.sprite
      end
    end
    self
  end

  def update direction
    @layers.count.times do |i|
      @xs[i] -= @speed * (i+1) * direction
      x_coord = @xs[i] % @w
      @sprites[i*3+0][:x] = x_coord - (@w - 1)
      @sprites[i*3+1][:x] = x_coord
      @sprites[i*3+2][:x] = x_coord + (@w - 1)
    end
    self
  end

  def render_into win
    Window.render_into win, @sprites
    self
  end
end