A MIDI keyboard in Shoes.

shoes_midi_keyboard.rb

# A very simple midi-keyboard with Shoes.
# No key-up Event.
# Set Keyboard layout here:
KEYBOARD_LAYOUT = :de # only :de and :us are supported, by now. See MidiKeymap#map_keys!
#
# You will need a midi input for this. 
# On OSX you could use http://notahat.com/midi_patchbay
# and http://notahat.com/simplesynth or Garage Band
# 
# enjoy.

Shoes.setup do
  gem 'midiator = 0.2.0' 
end
require 'midiator'

# Methods for drawing the piano keys
module ClaviatureDrawing
  module Highlightable
    def highlight
      self.style :stroke => app.fuchsia 
    end
    def unhighlight
      self.style :stroke => app.black
    end
  end
   
  def draw_keys    
    stroke black
    strokewidth 4 
    
    key_pattern = [:w,:b,:w,:b,:w,:w,:b,:w,:b,:w,:b,:w]
    keys = []    
    offset = 0  # FIXME Don't know, why i cannot use translate here.
    20.times do |i|
      key_type = key_pattern[i % key_pattern.length]
      case key_type
        when :w
          k = draw_white_key(offset)
          offset += 64
        when :b
          k = draw_black_key(offset)          
      end     
      k.extend Highlightable 
      keys << k
    end
    keys
  end
  
  def draw_white_key(offset)
    nofill
    rect offset, 0, 60, 130, 4
  end
  
  def draw_black_key(offset)
    fill black
    rect offset-20, 0, 40, 80, 4
  end
end

# Responsible for mapping Keystrings to Midi-tones.
class Keymap 
  attr_accessor :octave 
  
  def initialize(options = {})
    options = { 
      :layout => :de,
      :octave => 2
      }.merge!(options)    
    @octave = options[:octave]
    set_layout(options[:layout])
  end
    
  def midi_tone_of(keystring)
    # TODO Oktave richtig mit einberechnen!..
    (@octave+1) * 12 + @tones[keystring]
  end
  
  # Method to find out, which key has been pressed, the most left key is 0 ...
  def index_of(keystring)
    @tones[keystring]
  end
  
  private
  
  def set_layout(lang)
    @keys = {
      :de => %w(a w s e d f t g z h u j k o l p ö ä + # ),
      :us => %w(a w s e d f t g y h u j k o l p ; ' ] \\ )    
    }[lang] 
    map_keys!
  end    
  
  def map_keys!
    @tones = {}
    @keys.each_with_index do |k, i|     
      @tones[k] = i
    end
  end
end

# The Shoes App
Shoes.app(:title => "Midi Keyboard", :width => 766, :height => 136, :resizable => false) do    
  self.extend ClaviatureDrawing 
  
  def play(note, time)
    # Midiator sleeps for 'time' after each note, so we start a new threat (is this ok?)
    Thread.new { @midi.play(note, time) }  # note, duration, channel, velocity
  end
  
  def highlight(shape, time)
    shape.highlight    
    timer time do
      shape.unhighlight
    end
  end
    
  background yellow
    
  # setup midi driver
  @midi = MIDIator::Interface.new
  @midi.autodetect_driver
    
  # setup keymap
  @keymap = Keymap.new(:layout => KEYBOARD_LAYOUT)    
    
  # draw keys
  @key_shapes = draw_keys
  
  keypress do |key|
    case key
    when "1"
      @keymap.octave -= 1
    when "2"
      @keymap.octave += 1
    else
      t = 1
      play(@keymap.midi_tone_of(key), t)
      highlight(@key_shapes[@keymap.index_of(key)], t)
    end
  end
end