main.rb

#Testing differences between Shoes 2 and 3, Ruby 1.8 and Ruby 1.9
#In Shoes 2 (and also version 1229 of Shoes 3 that I built with Ruby 1.8) this code works
#In Shoes 3, then in ui.rb ":attach => Window" must be replaced with ":attach => Shoes::Window"
#as otherwise the error "uninitialized constant UI::Window" occurs.

require 'ui'

Shoes.app  do
	extend UI
	@content = stack do
		ui
	end
end

ui.rb

module UI
	def ui
		#In shoes 3, ":attach => Window" must be ":attach => Shoes::Window"
		flow :margin => 0, :attach => Window, :height => 50, :scroll => false do
			para "test"
		end
	end
end