
HIERARCHY OF VK KLASSES

 vk_object
   |
   +- vk_screen (todo)
   |
   +- vk_widget   
   |    |
   |    +- vk_container
   |    |    | 
   |    |    +- vk_frame (todo)
   |    |    
   |    +- vk_button
   |    |
   |    +- vk_label
   |    |
   |    +- vk_spinner
   |    |
   |    +- vk_listbox
   |         |
   |         + vk_menu
