Module layers 

Layers

Layers control the rendering order of elements. Elements in higher layers are rendered on top of those in lower layers.

Use the .layer() method with one of three variants:

• Layer::Relative(i16) (default): offset relative to the parent’s layer. Positive values render higher, negative values render lower.
• Layer::Overlay: jumps to a very high layer, useful for modals or tooltips that must appear above everything.
• Layer::RelativeOverlay(u8): similar to Overlay but you have multiple overlay layers options.

fn app() -> impl IntoElement {
    rect()
        .child(rect().layer(-1).child("Background")) // below default
        .child(rect().child("Content")) // default layer
        .child(rect().layer(1).child("Foreground")) // above default
        .child(rect().layer(Layer::Overlay).child("Modal")) // on top of everything
}

Note: The rendering order of elements within the same layer is not guaranteed. Always use distinct layer values when order matters.