Struct Morph 

pub struct Morph { /* private fields */ }

An interpolation between two RoundedPolygons: at any progress t it yields one closed outline, the start shape at 0 and the end shape at 1.

Cost

Building one is the expensive step — measuring both outlines, pairing their corners and re-cutting the curves all happen in Morph::new. Build a morph once and keep it (in widget state, a OnceLock, a cache keyed by the shape pair); Morph::path is the per-frame call and does nothing but interpolate the stored curve pairs into the path it returns.

Implementations

impl Morph

pub fn new(start: RoundedPolygon, end: RoundedPolygon) -> Morph

Builds the morph from start to end.

This measures both outlines, pairs their corners and re-cuts their curves into matching pairs — see Morph’s note on cost for why that belongs outside the frame loop.

Panics

If either polygon has no measurable outline, or if two corners of one shape sit at the same point along its outline (upstream throws in both cases; every input here is a shape definition, not runtime data).

pub const fn start(&self) -> &RoundedPolygon

The shape at progress 0.

pub const fn end(&self) -> &RoundedPolygon

The shape at progress 1.

pub fn as_cubics(&self, progress: f64) -> Vec<Cubic>

The morphed outline at progress, as its curves.

Allocates the returned list; Morph::path is the cheaper route when the caller only wants to paint it.

pub fn path(&self, progress: f64) -> BezPath

The morphed outline at progress as a closed kurbo::BezPath: one MoveTo, one CurveTo per curve, and a ClosePath.

progress is not clamped — a caller feeding a spring value may pass a little past 0/1 to keep the spring’s overshoot, as long as it stays close (far outside the range the outline is undefined).

This is the per-frame call: it allocates the path it returns and nothing else.

pub fn bounds(&self) -> Rect

The axis-aligned bounds of every anchor and control point of both shapes — cheap, and never tighter than Morph::exact_bounds.

This is the size to reserve for a morph: an interpolated control point is a blend of the two shapes’ own, so for any progress in 0..=1 the outline stays inside the hull these bounds describe (an overshooting progress can leave it).

pub fn exact_bounds(&self) -> Rect

The true axis-aligned bounds of both shapes’ outlines.

Holds the outline at progress 0 and 1 exactly; in between, an interpolated control point can pull a curve marginally outside it, which is why Morph::bounds is the safer reservation.

pub fn max_bounds(&self) -> Rect

The smallest square holding either shape in any rotation — what a UI element hosting a spinning morph needs to reserve.

Trait Implementations

impl Clone for Morph

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Morph

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.