Module zstack 

ZStack — a layout container that layers children on top of each other.

The container sizes itself to the maximum width and maximum height across all children, measured at an unspecified proposal so background rects do not inflate the size. Height additionally takes a width-bounded query when the parent bound the width, so a wrapping child reports the height it will really occupy rather than a single line; see layout_response for why that query is width-only. Each child is then offered the full container bounds and positioned according to the container-level Alignment (default: CENTER); individual children can override alignment via WidgetTree::set_alignment.

The primary use-cases are layered UIs — a background RectWidget beneath a TextWidget, a floating badge over a button icon — and card-like compositions where a paint layer and a content layer share the same bounds. Children that expand to fill their proposal (e.g. RectWidget) fill the full ZStack area; children with fixed intrinsic sizes are positioned by alignment.

Every layer is offered the stack’s full size, so a widget that answers proposal.resolve(0.0, 0.0) fills the whole stack. Being on top, it takes every press over the stack even with no handler, which is correct occlusion. An invisible helper layer (a frame-tick driver, say) should be .hit_transparent(true) or answer Size::ZERO.

Propagates shrink weight and minimum size when any child opts in, so wrapping a shrinkable single-line label in a ZStack stays shrinkable.

let _card = ZStack::new()
    .child(RectWidget::new().background(SurfaceRole::Raised))
    .child(TextWidget::new(lit!("Hello")));

Structs

ZStack

A layout container that stacks children on top of each other. Size = max of children sizes. Children are positioned according to the container’s Alignment (default: center), with per-child overrides.