A Builtin Player that adds the look and behavior of a native button. It may be applied in the PropBuilder DSL like so:

  my_button :players => "button"

Props including this Player should implement the button_pressed hook.

  def button_pressed(e)
    # do something
  end

Props including this Player may implement any of the key and focus event hooks:

  key_pressed, key_typed, key_released, focus_gained, focus_lost