Collapse

Collapse — a wrapper widget that animates its child between hidden and natural size when an external Signal<bool> toggles.

Drives a progress: Signal<f32> ∈ [0, 1] (0 = collapsed, 1 = expanded) and reports its own size as (natural_w, natural_h * progress) while the child lays out at full natural size — the framework's clip pass crops the overflow. This keeps the animation visible across the whole duration, instead of compressing the visible portion into the final few milliseconds (which is what happened when an animated MaxSize::max_height slid against a 10000-px sentinel that vastly overshot the child's natural height).

let expanded = ctx.signal(false);
ctx.add(Collapse::new(expanded.clone()).child(advanced_settings));
// ...elsewhere:
expanded.set(true);  // animates open over `motion.duration_collapse`

Honors prefers-reduced-motion: under reduced motion, progress snaps to its end value instead of tweening.

Builder methods at a glance

child, child_id

API reference

📖 Full rustdoc API for this module

pub struct Collapse

Wraps a child and animates it between hidden (progress=0) and natural size (progress=1), driven by an external Signal<bool>.

#![allow(unused)]
fn main() {
pub struct Collapse { /* fields */ }
}

Methods

pub fn new(expanded: Signal<bool>) -> Self

Build a collapse wrapper bound to expanded. Initially collapsed iff expanded.get() is false at the first build().

pub fn child(mut self, widget: impl Widget + 'static) -> Self

Inline child widget (deferred insertion).

pub fn child_id(mut self, id: WidgetId) -> Self

Pre-registered child by WidgetId.