anchor.diff:  
   procedure TfpgX11Drag.Dragging(ev: TXEvent);
   var
  -  dx, dy: cint;
  -  child: TWindow;
     lTarget: TWindow;
   begin
     lTarget := FindWindow(ev.xmotion.root, ev.xmotion.x_root, ev.xmotion.y_root);
  
positive.code:   child: TWindow;
    prevchild: TWindow;
  
    ret_root: TfpgWinHandle;
    ret_child: TfpgWinHandle;
    root_x, root_y: integer;
    child_x, child_y: integer;
  
    s: string;
    i: integer;
    lTargetWinHandle: TWindow;
    w: TfpgX11Window;
  
negative.code: var
    actualtype: TAtom;
    actualformat: cint;
    count, remaining: culong;
    data: PChar;
    lversion: culong;
  begin
  