private final void draw(final GC gc, final int offset, final int length) {
    if (gc != null) {
      Point left = mTextWidget.getLocationAtOffset(offset);
      Point right = mTextWidget.getLocationAtOffset(offset + length);
      Color color = mMismatch ? mMismatchColor : mColor;

      if (mBox) {
        gc.setForeground(color);
        int x = left.x;
        int y = left.y;
        int w = right.x - left.x - 1;
        int h = gc.getFontMetrics().getHeight();
        gc.drawRectangle(x, y, w, h);
      } else {
        gc.setForeground(mDefaultColor);
        gc.setBackground(color);
        gc.drawString(mTextWidget.getTextRange(offset, 1), left.x, left.y, false);
      }
    } else {
      mTextWidget.redrawRange(offset, length, true);
    }
  }