title: What is Win32 virtual key code 0xFF used for and is it documented somewhere?
body: <p>I have a netbook which supports multi-touch gestures on its touchpad.  When you do a three-finger swipe to the left or right, it will send some messages to the active window – for some windows this means sending page up/down keypresses.</p>
  
  <p>The actual messages that get sent for a swipe right are, according to Spy++:</p>
  
  <ul>
    <li>WM_KEYDOWN, virtual key = 0xFF</li>
    <li>WM_KEYDOWN, virtual key = VK_NEXT</li>
    <li>WM_KEYUP, virtual key = VK_NEXT</li>
    <li>WM_KEYUP, virtual key = 0xFF</li>
  </ul>
  
  <p>My question is: what is this 0xFF virtual key code, and is it documented somewhere?  There's no corresponding #define for it in winuser.h.</p>