viewport.shiftHorizontally(key == KeyCodeMap.ARROW_RIGHT);
return true;
case KeyCodeMap.ARROW_UP:
case KeyCodeMap.ARROW_DOWN:
viewport.shiftVertically(key == KeyCodeMap.ARROW_DOWN, false);
return true;
case KeyCodeMap.PAGE_UP:
case KeyCodeMap.PAGE_DOWN:
viewport.shiftVertically(key == KeyCodeMap.PAGE_DOWN, true);