Function card_extent 

pub fn card_extent(work: Rect, card: &Card) -> Size

How big card stands on work: every card in a column is as wide as the layer’s one column, so the cards share a width and an edge, and the layer’s place wins over what its app asked for. A card its app draws keeps the height its app asked for; every other card the height its summary’s rows take. The app lays its body out at the width the layer’s place gives it.