1. package Scrollables is 
  2.     pragma Preelaborate; 
  3.  
  4.     type Scrollable is limited interface; 
  5.     type A_Scrollable is access all Scrollable'Class; 
  6.  
  7.     function Get_Scroll_Inc_X( this : access Scrollable ) return Integer is abstract; 
  8.  
  9.     function Get_Scroll_Inc_Y( this : access Scrollable ) return Integer is abstract; 
  10.  
  11. end Scrollables;