Putting an hbox in a notebook tab

[Matt Bragano <maestro485 comcast net>]

I'm having a problem getting an hbox to show up in a notebook tab.  The 
hbox contains a label and a button, but when I use append_page(Widget& 
child, Widget& tab_label), the tab appears very small and empty.  If I 
insert either the label or the button alone, they appear, but not when 
placed in an hbox.

Are there any caveats pertaining to what can be included in a notebook 
tab, or is there something else I should be looking for?

Thanks,
Matt Bragano