How to mimic "vanilla processing" inner classes

Processing inner classes

Regular processing makes much use of java "inner classes" to make PApplet methods and variables available to the inner classes (with ruby-processing you can include Processing::Proxy module to achieve a similar result.

JRubyArt

Since JRubyArt version 0.2.5.pre Processing::Proxy module provide similar access, but now implemented using :method_missing to access PConstants, also include PConstants (or use PConstants::). However you can use ruby forwardable instead, to produce an even more elegant solution (inmho). See Node class below:-

require 'forwardable'

class Node < Physics::VerletParticle2D
  extend Forwardable
  def_delegators(:@app, :fill, :stroke, :stroke_weight, :ellipse)
  def initialize(pos)
    super(pos)
    @app = $app
  end

  # All we're doing really is adding a display function to a VerletParticle
  def display
    fill(50, 200, 200, 150)
    stroke(50, 200, 200)
    stroke_weight(2)
    ellipse(x, y, 16, 16)
  end
end

To be even more kosher you could replace the global $app via an extra initialize argument.