Trait Decorate 

pub trait Decorate: Piece + Sized {
    // Provided methods
    fn id(self, id: impl Into<String>) -> AnyPiece { ... }
    fn id_of(self, id: impl Fn() -> String + 'static) -> AnyPiece { ... }
    fn id_keyed(self, prefix: &'static str, key: impl Display) -> AnyPiece { ... }
    fn tweak(self, f: impl FnOnce(RNode) + 'static) -> AnyPiece { ... }
    fn selectable(self) -> AnyPiece { ... }
    fn native_ref(self, r: &NativeRef) -> AnyPiece { ... }
    fn padding(self, insets: impl IntoInsets) -> AnyPiece { ... }
    fn max_width(self, max: f64) -> AnyPiece { ... }
    fn frame(self, width: f64, height: f64) -> AnyPiece { ... }
    fn width(self, width: f64) -> AnyPiece { ... }
    fn height(self, height: f64) -> AnyPiece { ... }
    fn a11y(
        self,
        f: impl FnOnce(A11yBuilder) -> A11yBuilder + 'static,
    ) -> AnyPiece { ... }
    fn on_tap(self, f: impl Fn() + 'static) -> AnyPiece { ... }
    fn focused<M>(self, binding: impl IntoFocusBinding<M>) -> AnyPiece { ... }
    fn context_menu(self, items: Vec<MenuEntry>) -> AnyPiece { ... }
    fn on_drag(self, f: impl Fn(Drag) + 'static) -> AnyPiece { ... }
    fn background<M>(self, color: impl IntoReactive<Color, M>) -> AnyPiece { ... }
    fn corner_radius(self, radius: f64) -> AnyPiece { ... }
    fn opacity<M>(self, opacity: impl IntoReactive<f64, M>) -> AnyPiece { ... }
    fn transform<M>(self, t: impl IntoReactive<Transform, M>) -> AnyPiece { ... }
    fn scale<M>(self, factor: impl IntoReactive<f64, M>) -> AnyPiece { ... }
    fn rotation<M>(self, degrees: impl IntoReactive<f64, M>) -> AnyPiece { ... }
    fn translation<Mx, My>(
        self,
        x: impl IntoReactive<f64, Mx>,
        y: impl IntoReactive<f64, My>,
    ) -> AnyPiece { ... }
    fn animation(self, anim: AnimSpec) -> AnyPiece { ... }
    fn modifier(self, m: impl Modifier) -> AnyPiece { ... }
    fn overlay(self, over: impl Piece) -> AnyPiece { ... }
    fn overlay_aligned(self, align: Alignment, over: impl Piece) -> AnyPiece { ... }
    fn grow(self) -> AnyPiece { ... }
    fn grow_w(self) -> AnyPiece { ... }
    fn grow_h(self) -> AnyPiece { ... }
    fn grid_span(self, n: usize) -> AnyPiece { ... }
    fn grid_align(self, a: Alignment) -> AnyPiece { ... }
    fn defers_system_gestures(self, edges: Edges) -> AnyPiece { ... }
    fn interactive_dismiss_disabled(self) -> AnyPiece { ... }
    fn any(self) -> AnyPiece { ... }
}

Provided Methods

fn id(self, id: impl Into<String>) -> AnyPiece

Stable element identifier: a11y identifier + dayscript locator + lint uniqueness (§5.5).

fn id_of(self, id: impl Fn() -> String + 'static) -> AnyPiece

Reactive element id — the id for rows inside a recycling list. A plain id is assigned once at build, but a recycled cell REBINDS to different items over its life (and drag-to-reorder rebinds eagerly), so a static item-derived id keeps naming the first-bound item. This variant re-registers whenever the closure’s value changes — read your ItemSlot inside it: .id_of(move || format!("row-remove-{}", slot.key())).

fn id_keyed(self, prefix: &'static str, key: impl Display) -> AnyPiece

Keyed id for collection items: rendered prefix:key (§5.5).

fn tweak(self, f: impl FnOnce(RNode) + 'static) -> AnyPiece

Apply a tweak: f runs once at mount, after the native widget exists, with the realized node (docs/tweaks.md). Reach the typed native handle through the compiled backend’s ext accessor (day_appkit::with_native, day_gtk::with_native, …) — or apply a packaged day-tweak-* crate’s modifier instead of calling this directly. If the native change affects the widget’s intrinsic size, follow it with day_core::invalidate_size. Day may overwrite managed properties (title, value, enabled, frame, a11y) on its next patch; unmanaged properties are stable.

fn selectable(self) -> AnyPiece

Make this piece’s text user-selectable — the reader can select and copy it (docs/text.md). Most useful on a label: text is NOT selectable by default on any backend, matching each platform’s native behavior. Applied to the piece’s own widget, so on a container it makes all the text within it selectable.

Best-effort: a backend with a native selection affordance for the widget honors it (AppKit, UIKit-less desktop toolkits, GTK, Qt, XAML, HarmonyOS, Android, web); one without leaves the text unselectable rather than erroring. Selection visuals and the copy shortcut are the platform’s own. Unmanaged — set once at mount, and it survives Day’s text updates.

fn native_ref(self, r: &NativeRef) -> AnyPiece

Capture a NativeRef to this piece’s realized node for later imperative access (docs/tweaks.md). The ref clears automatically when the piece’s scope is disposed.

fn padding(self, insets: impl IntoInsets) -> AnyPiece

fn max_width(self, max: f64) -> AnyPiece

Cap this piece’s width at max points: the child is never PROPOSED more, so text wraps inside the cap (chat bubbles, readable columns) while narrower content hugs.

fn frame(self, width: f64, height: f64) -> AnyPiece

fn width(self, width: f64) -> AnyPiece

Fix this piece’s WIDTH to width points while its height stays flexible (hugging its content or filling on the cross axis). The single-axis complement to Self::frame — e.g. a fixed-width sidebar pane in a row whose height fills the window.

fn height(self, height: f64) -> AnyPiece

Fix this piece’s HEIGHT to height points while its width stays flexible. The single-axis complement to Self::frame — e.g. a fixed-height header/toolbar bar that fills its width.

fn a11y(self, f: impl FnOnce(A11yBuilder) -> A11yBuilder + 'static) -> AnyPiece

fn on_tap(self, f: impl Fn() + 'static) -> AnyPiece

Fire when this piece is tapped (bounding-box; shapes override with path-precise testing).

fn focused<M>(self, binding: impl IntoFocusBinding<M>) -> AnyPiece

Bind this control’s keyboard focus to a signal (docs/focus.md), two-way like every other binding: native focus changes write the signal; writing the signal moves focus. Takes a Signal<bool> for one control, or (Signal<Option<K>>, K::Variant) binding one control of a group — writing false/None resigns focus (dismissing the soft keyboard on mobile). Focus applies asynchronously: a write is a request, resolved on the next turn, and the signal always ends up reflecting what the platform actually did.

fn context_menu(self, items: Vec<MenuEntry>) -> AnyPiece

Attach a context menu, shown with the platform’s native affordance on secondary-click (desktop) or long-press (mobile). Items are built with menu_item/sub_menu/menu_role/ menu_separator. Passing an empty Vec removes any menu.

fn on_drag(self, f: impl Fn(Drag) + 'static) -> AnyPiece

Fire on each phase of a drag over this piece.

fn background<M>(self, color: impl IntoReactive<Color, M>) -> AnyPiece

Fill the piece’s bounds with a solid color painted behind it — a message-bubble / card / badge surface. Accepts a constant Color, a Signal<Color>, or a Fn() -> Color; a reactive color repaints the surface when its source changes. Wraps the piece in a native container that carries the fill, so it composes with Self::corner_radius for a rounded colored surface and with Self::padding for interior inset.

fn corner_radius(self, radius: f64) -> AnyPiece

Round the piece’s corners to radius points, clipping its background and content to the rounded rectangle. Compose after Self::background for a rounded colored surface, or use alone to round a clipped child (e.g. an avatar image).

fn opacity<M>(self, opacity: impl IntoReactive<f64, M>) -> AnyPiece

Animate/set the piece’s opacity (0.0 transparent … 1.0 opaque). Wrapped in a native layer so it composes with .background; the change animates when made inside with_animation or under a .animation ancestor (§8.4).

fn transform<M>(self, t: impl IntoReactive<Transform, M>) -> AnyPiece

Apply an animatable Transform (translate/scale/rotate about the center) — the cheap movement/scaling channel that never triggers relayout (§8.4). Prefer this over .offset for animated motion.

fn scale<M>(self, factor: impl IntoReactive<f64, M>) -> AnyPiece

Uniformly scale the piece by factor about its center (animatable). Convenience over Self::transform.

fn rotation<M>(self, degrees: impl IntoReactive<f64, M>) -> AnyPiece

Rotate the piece by degrees clockwise about its center (animatable).

fn translation<Mx, My>( self, x: impl IntoReactive<f64, Mx>, y: impl IntoReactive<f64, My>, ) -> AnyPiece

Translate the piece by (x, y) points WITHOUT relayout (animatable) — the animation-friendly sibling of .offset.

fn animation(self, anim: AnimSpec) -> AnyPiece

Attach an implicit animation (§8.4): changes to this piece’s — and its descendants’ — animatable properties animate with anim even outside a with_animation. SwiftUI’s .animation. The ambient with_animation takes precedence when both apply.

fn modifier(self, m: impl Modifier) -> AnyPiece

Apply a Modifier — or, via the blanket impl, a plain FnOnce(AnyPiece) -> AnyPiece closure — to this piece. Pure composition: content.modifier(m) == m.apply(content.any()).

fn overlay(self, over: impl Piece) -> AnyPiece

Draw over on top of this piece, centered, WITHOUT affecting layout size — a badge / annotation overlay. self is the sizing content (bottom of the z-order); over is proposed self’s size and drawn on top. For an explicit alignment use Self::overlay_aligned; for a stack that sizes to the UNION of its children use zstack.

fn overlay_aligned(self, align: Alignment, over: impl Piece) -> AnyPiece

Self::overlay with an explicit Alignment for the annotation (e.g. a corner badge with Alignment::TopTrailing).

fn grow(self) -> AnyPiece

Expand to fill the available space on both axes (a filling pane / card that stretches to its container). Wraps the piece in a layout-only node carrying grow [Flex] — the stack offers it the space and it fills; no native backing, so this is a pure layout change.

fn grow_w(self) -> AnyPiece

Expand to fill the available horizontal space.

fn grow_h(self) -> AnyPiece

Expand to fill the available vertical space.

fn grid_span(self, n: usize) -> AnyPiece

Span n columns (n ≥ 1) of the enclosing grid (docs/grid.md). Grid modifiers set facts on the node the grid sees: apply them LAST (outermost), like .grow_w() — an outer wrapper would hide the facts from the grid.

fn grid_align(self, a: Alignment) -> AnyPiece

Override this cell’s alignment within its cell rect of the enclosing grid (docs/grid.md). Apply LAST (outermost), like Self::grid_span.

fn defers_system_gestures(self, edges: Edges) -> AnyPiece

While this subtree is mounted, ask the OS to require a second swipe for its edge gestures on edges (docs/cover.md) — the SwiftUI defersSystemGestures(on:) analogue. Put it on a game or drawing surface whose touches run to the screen edge, so a swipe up from the bottom doesn’t leave the app. iOS defers the chosen edges’ system gestures; Android enters swipe-to-reveal immersive mode while any subtree requests deferral; desktop backends no-op.

fn interactive_dismiss_disabled(self) -> AnyPiece

While this subtree is mounted, the enclosing cover (or other modal surface) must not be dismissed interactively — the SwiftUI interactiveDismissDisabled() analogue (docs/cover.md). System back / sheet gestures are ignored; only programmatic writes (an explicit close control) dismiss it.

fn any(self) -> AnyPiece

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<P: Piece> Decorate for P