Using inner tabbox in tabbox, when change to vertical the content of inner tabbox didn't show.
And either set hflex="1" in inner tabbox or remove <window> tag the issue disappeared.
<zk>
<window title="Tabbox" border="normal">
<tabbox orient="horizontal">
<tabs>
<tab label="Data Binder" />
</tabs>
<tabpanels>
<tabpanel>
<checkbox id="vertical2" label="vertical" onCheck='box.setOrient(self.isChecked() ? "vertical" : "horizontal")'/>
<tabbox id="box" orient="horizontal">
<tabs width="40px">
<tab label="input" />
<tab label="grid" />
</tabs>
<tabpanels>
<tabpanel>
input
</tabpanel>
<tabpanel>
grid
</tabpanel>
</tabpanels>
</tabbox>
</tabpanel>
</tabpanels>
</tabbox>
</window>
</zk>