The structure of the dialog is pretty complicated, but is all just logical nasal stuff and has nothing to do with the canvas - nasal interaction.
In principle, all pages are parsed separately so they can be turned on and off easily. In general, when a tab is pressed, all pages are hidden (except for the menu) and the proper page shown.
This happens when the GEAR tab in the menu is pressed. The menu is re-setted and then the gear tab is changed color to indicate it is selected.
All the other pages are hidden, the gear page is show and finally all gear-buttons are updated. The status of the buttons depends on fg-properties. They have no listeners, but are only updated when the page is show. This is a bit easier and saves a lot of listeners. The disadvantage is that the buttons (they change color when a pressed and a failure is initiated) are not updated automatically. Maybe not ideal for a 'front end'...