code: private void txtWhitespaceWidthFocusLost(java.awt.event.FocusEvent evt) {//GEN-FIRST:event_txtWhitespaceWidthFocusLost
          // TODO: the name (and label?) of this text box no longer matches its purpose
          if (txtWhitespaceWidth.getText().matches("[0-9]+")) {
              quietZoneVertical = Integer.parseInt(txtWhitespaceWidth.getText());
              encodeData();
          } else {
              txtWhitespaceWidth.setText(String.valueOf(quietZoneVertical));
          }
      }
docs: GEN-LAST:event_txtXDimensionFocusLost