reuse_window.rb

require 'singleton'
require 'gosu'

class TestGameWindow < Gosu::Window
  include Singleton

  def initialize
    super(640, 480, false)
    self.caption = "Esc = quit"
  end

  def draw
    @draw_block.call if @draw_block
  end

  def button_down(id)
    close if id == Gosu::KbEscape
  end

  def while_showing(&block)
    @draw_block = block
    show
  end
end

window = TestGameWindow.instance

@img = Gosu::Image.from_text(window, "test", Gosu.default_font_name, 20)
window.while_showing do
  @img.draw(10, 10, 0)
end

@img2 = Gosu::Image.from_text(window, "test2", Gosu.default_font_name, 20)
window.while_showing do
  @img2.draw(10, 10, 0)
end