Experiments with ruby-processing (processing-2.2.1) and JRubyArt for processing-3.0

Friday, 8 February 2013

A graphical example of deep jruby voodoo in ruby-processing

More experiments with casting a jruby class to a java class, which seems to be required to use the processing-2.0 feature of registerMethod (uses reflection, very unwise to mind). Known "methods" include pre, draw, mouseEvent, keyEvent, dispose.

Here is the sketch code test_register.rb:-
# A simple demonstration of vanilla processing # 'reflection' methods 
# in ruby-processing see register_send.rb for the guts...

require_relative 'register_send'

def setup
  size 200, 200
  RegisterSend.new self

def draw
  fill(0, 0, 200)
  ellipse(120, 120, 60, 60)
Here's where the voodoo gets done in register_send.rb (ruby class becomes a java class and registers methods with the processing $app):-
require 'jruby/core_ext' # required to allow become_java!

# This class demonstrates how to use 'reflection' methods in ruby-processing
# NB: the class must become a java object to get registered. This is an
# advanced feature in vanilla processing, mainly used by libraries.
class RegisterSend
  attr_reader :parent

  def initialize(parent)
    @parent = parent
    parent.java_send :registerMethod, [java.lang.String, java.lang.Object], :draw, self
    parent.java_send :registerMethod, [java.lang.String, java.lang.Object], :pre, self

  def pre
    puts 'before draw'

  def draw
    puts 'at begin draw...'
    parent.fill(200, 100)
    parent.ellipse(100, 100, 60, 60)
  # putting become_java! here works OK
Here is the resulting sketch and the console, shows output to console:-

Actually I'm a bit worried about all this voodoo, it's bad enough that processing is making so much use of this reflection crap, without me making it worse here. Also I can't seem to register either mouseEvent or keyEvent as yet (methods requiring parameters which should probably be a simple java object, that can get cast later to an event?).

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I have developed JRubyArt and propane new versions of ruby-processing for JRuby- and processing-3.2.2