Refactoring a Shoes widget. Needs midiator gem.

after.rb

class Piano < Widget
  def initialize opts = {}, &action
    opts = {:width => 700, :height => 100}.merge opts
    @action = action
    
    key_width = opts[:width] / 52.0
    ivory = {:bottom => 0, :width => key_width.round, :height => opts[:height] * 2 / 5}
    ebony = {:top => 0, :width => (key_width * 2 / 3).round, :height => opts[:height] * 3 / 5}
    
    last_x = -key_width
    stack(opts) {
      background white; stroke black
      (21..109).each do |note|
        x = last_x.round
        if [0, 2, 4, 5, 7, 9, 11].include? note % 12
          last_x += key_width
          midi_button ivory.merge(:left => x), gray(0,0), note
          line x, 0, x, opts[:height]
        else
          midi_button ebony.merge(:left => x + ebony[:width]), black, note
        end
      end
    }
    @midi = MIDIator::Interface.new
    @midi.autodetect_driver
  end
  def play note
    @midi.play(note, 0.1, 2, 100)
    @action.call(note) if @action
  end
  def midi_button rect, color, note
    stack(rect) { background color; click { play note } }
  end
end

before.rb

class Keyboard < Widget
  attr_accessor :target
  def initialize opts = {}
    @width, @height = opts[:width], opts[:height]
    white_notes = [0, 2, 4, 5, 7, 9, 11]
    key_width = @width / 52.0
    last_x = -key_width
    white_keys = stack(:top => 0, :left => 0, :width => @width, :height => @height)
    black_keys = stack(:top => 0, :left => 0, :width => @width, :height => @height)
    stroke black
    flow(:width => @width, :height => @height) {
      (21..109).each do |number|
        scale_note = number % 12
        if white_notes.include? scale_note
          last_x += key_width
          x, y, w, h, c, s = last_x.to_i, 0, key_width.to_i, @height, white, white_keys
          line last_x.to_i, 0, last_x.to_i, @height
        else
          x, y, w, h, c, s = (last_x + key_width * 2 / 3).to_i, 0,
                             (key_width * 2 / 3).to_i, @height * 2 / 3,
                             black, black_keys
        end
        s.append { midi_button({:left => x, :top => y, :width => w, :height => h}, c, number) }
      end
    }
    @midi = MIDIator::Interface.new
    @midi.autodetect_driver
  end
  def play_note number
    @midi.play(number, 0.1, 2, 100)
  end
  def midi_button(r, c, n)
    stack(r) { background c; click {|button, x, y| play_note(n); target.call(n) if target} }
  end
end