A container to hold the set of pages in a tabbox. The tabpanels element should be placed in a tabbox although it does not have to be a direct child. The children of the tabpanels element become the panels of the tabbox. In most cases you would use a vbox, but they can be any element, although some people like to use tabpanel elements. By clicking the first tab, the first panel will be displayed. By clicking the second tab, the second panel will be displayed and so on. There should be the same number of panels as there are tabs. Panels should never be hidden; hiding the tab suffices to make the panel inaccessible.
Returns the index of the currently selected item. You may select an item by assigning its index to this property. By assigning -1 to this property, all items will be deselected. Returns -1 if no items are selected
Holds a reference to the currently selected panel within a <tabbox> element. Assigning a value to this property will modify the selected panel. A select event will be sent when the selected panel is changed.