layout.defaults

When called, this checks to see which layouts have not already been provided (using layout.provides). For each required kind of layout that hasn't been provided, this calls the corresponding layout.classic_ function. This ensures that all required layouts are provided, even in later versions of Ren'Py.

It's safe to call this more than once, as the second call will be a no-op, since all layouts will have been provided by the first call.