code: private static void ensureSameWidgetSize(final DecoratedTabPanel panel) {
      if (!panel.isAttached()) {
        throw new IllegalArgumentException("panel not attached: " + panel);
      }
      int maxw = 0;
      int maxh = 0;
      for (final Widget widget : panel) {
        final int w = widget.getOffsetWidth();
        final int h = widget.getOffsetHeight();
        if (w > maxw) {
          maxw = w;
        }
        if (h > maxh) {
          maxh = h;
        }
      }
      if (maxw == 0 || maxh == 0) {
        throw new IllegalArgumentException("maxw=" + maxw + " maxh=" + maxh);
      }
      for (final Widget widget : panel) {
        setOffsetWidth(widget, maxw);
        setOffsetHeight(widget, maxh);
      }
    }
docs: Ensures all the widgets in the given panel have the same size.
  Otherwise by default the panel will automatically resize itself to the
  contents of the currently active panel's widget, which is annoying
  because it makes a number of things move around in the UI.
  @param panel The panel containing the widgets to resize.