search up the tree for our layer, and apply layer to our kids

its a pita but its quite hard to cache the layer for a widget when it
might not be in a layer when added to the container. better just to take
the hit at tree construction
drop all layers when entering the main loop
do the error dialog with a Label and Table so it collapses to centre

I need to work out how to put a MultiLineText in a variable-size
container