public void onBeforeSelection(BeforeSelectionEvent<Integer> bse) {
buttonClicked = true;
TabBar tb = (TabBar) bse.getSource();
cSelIdx = tb.getSelectedTab();
int selIdx = bse.getItem();
TabHolder th = findTab(selIdx, tb);
if (!th.button.isUseDropdown()) {
th.button.activate();
bse.cancel();
} else {
dropdown.clearHeaderBar();
}
}
