emit before/after show/hide extra signals on the current stack widget
emit before/after show/hide signals like StackWidget
only emit before/after show/hide signals if widget is mounted
update order of setting internal current index
update order of setting internal current index
add an explicit method to clear a pending children resize
only resize the current child, and resize it when shown
allow a subclass to dictate which children to resize
drop the resize collection method
update dock panel child resizing
code order
cleanup