The :class:`Layout` class itself cannot be used directly.
example, 0.5 is 50%, 1 is 100%.
'''This function is called when a layout is called by a trigger.
directly but use :meth:`_trigger_layout` instead.
positions of e.g. children should be scheduled for the next frame.
widgets given (potential) min or max bounds on the widgets' size.
The ``hint`` list is updated with appropriate sizes.
things out according to constraints using size hints.
The sum of the size hints (basically ``sum(size_hint)``).
whose size hint is not None. Cannot be zero.
Items in the iterable are the size_hint_min for each widget.
Items in the iterable are the size_hint_max for each widget.
Nothing. ``hint`` is updated in place.
# most allowed, proportionately to their size (or inverse size hint).
# larger sh get reduced less, and those with smaller, more.