ruby-processing

Using the LibraryProxy in your sketches

In the sketch you should load_library :library_proxy and your library class should inherit from LibraryProxy and implement pre(), draw() and post() methods (can be empty method if not required). For simplicity initialize your processing library in the sketch setup.

Example library

require 'forwardable'

# A custom Array created using forwardable (that can also access the PApplet pre,
# post and draw loops by extending our new LibraryProxy class. Also has access
# to custom background(int), fill(int) and stroke(int) methods.
class CustomArray < LibraryProxy
  extend Forwardable
  def_delegators(:@objs, :each, :<<)
  include Enumerable

  attr_reader :app

  # We must initialize class with the PApplet instance
  def initialize(app)
    @app = app
    @objs = []
  end

  def add_object(mx, my, x, y, speed)
    self << Particle.new(x.to_i, y.to_i, mx, my, Sketch::UNIT, speed, 1, 1)
  end

  # Access the processing post loop (gets called after draw)
  def post
    each do |obj|
      update_x obj
      next unless obj.y >= Sketch::UNIT || obj.x <= 0
      obj.ydir *= -1
      obj.y += obj.ydir
    end
  end

  def update_x(obj)
    obj.x += obj.speed * obj.xdir
    return if (0..Sketch::UNIT).cover? obj.x
    obj.xdir *= -1
    obj.x += obj.xdir
    obj.y += obj.ydir
  end

  # We need this to fulfill the contract of implementing abstract methods of
  # LibraryProxy which is an alias for Java::ProcessingCore::AbstractLibrary
  def pre
  end

  # Access the processing draw loop here, using our custom background and fill
  # note: use of 'app' to access ellipse functionality as would otherwise be
  # required for background and fill
  def draw
    background(0)
    fill(255)
    each do |obj|
      app.ellipse(obj.mx + obj.x, obj.my + obj.y, 6, 6)
    end
  end
end

# The Particle object

Particle = Struct.new(:x, :y, :mx, :my, :size, :speed, :xdir, :ydir)

Example sketch

# A minimalist sketch that demonstrates a possible approach to creating a custom
# array of objects using forwardable. Also demonstrates how to use LibraryProxy.

load_library :library_proxy     # loads the JRubyArt LibraryProxy abstract class
require_relative 'custom_array' # loads our custom 'library' class

UNIT = 40

def setup
  size 640, 360
  wide_count = width / UNIT
  height_count = height / UNIT
  custom_array = CustomArray.new(self)
  height_count.times do |i|
    wide_count.times do |j|
      custom_array.add_object(j * UNIT, i * UNIT, UNIT / 2, UNIT / 2, rand(0.05..0.8))
    end
  end
  no_stroke
end

# does nothing here see custom_array.rb
def draw
end