CrystGLFW::Event::WindowClose
A CrystGLFW::Event::WindowClose is generated when a Window is closed. It is yielded to the block defined by on_close.
window = Window.new
window.on_close do |event|
  puts "Bye!"
end
window
You can retrieve the event's associated Window using the window method:
event.window # => CrystGLFW::Window