private void initContent() {
   if (screenText == null) {
     fieldPositions = new ArrayList<TerminalPosition>();
     screenText = SnapshotUtils.initSnapshot(getRows(), getSize(), fieldPositions);
   }
 }
 public String getText(TerminalPosition position, int length) {
   initContent();
   return SnapshotUtils.getText(screenText, getSize(), position, length);
 }
 public TerminalField getField(TerminalPosition position) {
   return SnapshotUtils.getField(this, position);
 }