title: Hide or change mouse pointer in Linux/X11 when pointer is actively grabbed by others
body: <p>I failed to hide or change mouse pointer when mouse pointer is actively grabbed by some other client.</p>
  
  <p>I have tried XChangeActivePointerGrab and XDefineCursor.
  Main question is: During XDnD (Drag and Drop), when the mouse pointer enters my window, I cannot hide it.</p>
  
  <p>I am going to use that in Synergy: When user is dragging something to another display (on some other computer) mouse pointer on the first one should be hidden.</p>