Crate frust

Expand description

Facade crate: the public frust framework API.

App authors depend on this single crate. It exposes run, the canonical app entry point, and curates the view/widget/reactive vocabulary from the underlying framework crates so the declarative call shape reads exactly as the spec promises:

use frust::{AnyView, Column, Component, View, any, text};

// A small stateless widget: a plain fn, generic over the state of
// whichever component places it.
fn greeting<S: 'static>(message: &str) -> impl View<S> + use<S> {
    text(message.to_owned()).size(24.0)
}

struct Counter;

impl Component for Counter {
    type State = i32;

    fn init(&self) -> i32 {
        0
    }

    // The whole UI lives in `build`; split it into widget fns like
    // `greeting` rather than nesting ever deeper inside it.
    fn build(&self, state: &mut i32) -> AnyView<i32> {
        any(Column(vec![
            any(greeting("Hello from Frust")),
            any(text(format!("count: {state}")).size(32.0)),
        ]))
    }
}

frust::run(Counter).unwrap();

The composition rule: stateless pieces are plain widget functions called from build; a piece with its own state is a child Component mounted with component, which gives it a private state boundary. run (or the app! macro, which also covers the mobile and web shells) starts it.

§Low-level escape hatch: `App::new`

App is the low-level primitive run and app! expand into (App::new(state, move |state| root.build(state))): a single ambient State and a build closure, with no Component state-boundary or retained local state. Ordinary apps use a Component with run or app!; reach for App::new directly only when you need that raw (state, build) pair:

struct AppState {
    greeting: String,
}

let build = |state: &mut AppState| -> frust::AnyView<AppState> {
    frust::any(frust::text(state.greeting.clone()).size(32.0))
};

frust::App::new(AppState { greeting: "Hello from Frust".into() }, build)
    .run()
    .unwrap();

§Layout containers

The primitive containers compose heterogeneous children through any (type erasure) into the declarative call shape:

use frust::{Align, Alignment, Column, EdgeInsets, Padding, Row, SizedBox, any, text};

struct Layouts;

impl frust::Component for Layouts {
    type State = ();

    fn init(&self) {}

    fn build(&self, _state: &mut ()) -> frust::AnyView<()> {
        any(Column(vec![
            any(text("title").size(24.0)),
            any(Row(vec![any(text("left")), any(text("right"))])),
            any(Padding(EdgeInsets::all(8.0), text("padded"))),
            any(Align(Alignment::CENTER, text("centered"))),
            any(SizedBox(Some(0.0), Some(12.0))),
        ]))
    }
}

Re-exports§

pub use frust_core::accesskit;
pub use kurbo;
pub use peniko;

Modules§

authoring: Everything needed to author a custom View/Widget pair.
icons: The vendored Material Symbols starter icon set, flat-re-exported so app code names frust::icons::HOME rather than the underlying frust-widgets crate. Each entry is an IconSource usable directly with icon; an app can also supply its own vector icons via IconData::from_path. Vendored Material Symbols starter set — GENERATED, do not hand-edit.
input: Pure input/gesture helpers (slop constants, input::VelocityTracker, the fling-decay math) re-exported for app authors and advanced widgets.
motion: The motion module: declarative implicit-animation wrappers (AnimatedOpacity/AnimatedScale today; switcher/patterns land later) over frust-core’s anim vocabulary. Re-exported wholesale (pub use frust_widgets::motion;), mirroring frust_widgets::icons’s existing wholesale-module precedent — the only other one in this facade — so later types under frust_widgets::motion ride along under frust::motion::* with no further facade edits (see that module’s own docs for the full rationale).

Macros§

android_app: Bind a generated app’s State/build to the fixed Android JNI exports (a Makepad app_main! precedent).
app: The canonical app entry point: one line binds a root Component to all three platforms.
ios_app: Bind a generated app’s State/build to the fixed iOS C-ABI exports (Makepad app_main! precedent).
web_app: The browser counterpart of android_app!/ios_app!: binds a Component’s state and build closure to the browser shell’s wasm-bindgen entry point. Takes the identical two-argument (state type + build expression, state built via Default) / three-argument (state type + explicit state-init expression + build expression) shape android_app! does, and app! drives it through the three-argument form exactly the way it drives android_app!/ios_app! (see @emit_mobile below) — most apps reach this through app!/web_app! rather than hand-writing the explicit state_init form.

Structs§

AlignView: A declarative alignment container. See the module docs.
Alignment: A relative alignment within a box: each axis runs -1.0 (start) through 0.0 (center) to 1.0 (end).
AlwaysScrollable: Flutter’s AlwaysScrollableScrollPhysics: accept a drag whether or not there is anything to scroll, and defer everything else to the chained parent.
AnimationController: The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. A 0.0..=1.0 animation value driven either by a duration + Curve or by a Spring fling.
AnyView: A type-erased View: lets a piece of UI change its concrete view type between frames (e.g. a conditional if cond { text(..) } else { button(..) }) while still fitting the statically-typed rebuild machinery.
App: A Frust application: the app state plus the build closure that maps it to a view tree.
BackHandler: Android back-press ⇄ navigator auto-wiring: attach_back_handler/BackHandler pop a NavigatorController on a platform back press and keep frust-reactive‘s handles_back flag in sync with the stack depth, so a shell knows whether a root-level back should fall through to the platform (activity finish). Mirrors RouterDeepLinks’s shape and, like it, is the ONLY place in the facade that sees both frust-widgets’ NavigatorController and frust-reactive’s back-press source together — see BackHandler’s doc for the consume/dedupe and timing contracts. Call BackHandler::track from every Component::build. Android back-press ⇄ navigator auto-wiring: attach_back_handler/BackHandler pop a NavigatorController on a platform back press and keep frust-reactive‘s handles_back flag in sync with the stack depth, so a shell knows whether a root-level back should fall through to the platform (activity finish). Mirrors RouterDeepLinks’s shape and, like it, is the ONLY place in the facade that sees both frust-widgets’ NavigatorController and frust-reactive’s back-press source together — see BackHandler’s doc for the consume/dedupe and timing contracts. Call BackHandler::track from every Component::build. Android back-press ⇄ navigator auto-wiring: attach_back_handler/BackHandler pop a NavigatorController on a platform back press and keep frust-reactive‘s handles_back flag in sync with the stack depth, so a shell knows whether a root-level back should fall through to the platform (activity finish). Mirrors RouterDeepLinks’s shape and, like it, is the ONLY place in the facade that sees both frust-widgets’ NavigatorController and frust-reactive’s back-press source together — see BackHandler’s doc for the consume/dedupe and timing contracts. Call BackHandler::track from every Component::build. A NavigatorController wired to the process-wide back-press source (see the module docs) — the explicit back-wiring surface predating the automatic navigator auto-wiring.
BackPresses: The Android back-press source (frust-reactive’s process-wide back source — see its back module docs). A mobile shell delivers a hardware/gesture back press via push_back_press, and the facade’s BackHandler reads it via back_presses to pop a navigator; set_handles_back/handles_back are the “framework consumes the next back” flag a shell polls to decide whether a root-level back falls through to the platform. App code normally uses attach_back_handler rather than these directly; push_back_press is also the desktop dev seam (no shell writes on desktop yet). The app-facing back-press read surface (see the module docs). Obtained via back_presses (frust::back_presses() at the facade).
Bouncing: iOS’s scroll feel — Flutter’s BouncingScrollPhysics: a drag may pull the position past an edge against a friction factor that tightens with depth, nothing is ever boundary-rejected, and a release runs an exponential friction curve that hands over to a rubber-band spring at whichever edge it reaches.
ButtonView: A declarative pressable button. See the module docs.
CanvasView: Declarative custom painting over the [PaintScene] trait object — a chart, a node-and-edge graph, a game board — without hand-rolling a View/ Widget pair. canvas takes a paint closure that runs in local space (the widget’s own top-left is always (0, 0), and painting past its own size is clipped, never a bug to chase) — flat-re-exported from frust-widgets so app code never names that crate directly. See CanvasView’s own doc for the full builder contract (.size/.expand sizing, .on_hit-gated .on_tap/.on_pointer, and .repaint_key for paint-only dirtying driven by data outside the ordinary View diff).
CanvasWidget: Declarative custom painting over the [PaintScene] trait object — a chart, a node-and-edge graph, a game board — without hand-rolling a View/ Widget pair. canvas takes a paint closure that runs in local space (the widget’s own top-left is always (0, 0), and painting past its own size is clipped, never a bug to chase) — flat-re-exported from frust-widgets so app code never names that crate directly. See CanvasView’s own doc for the full builder contract (.size/.expand sizing, .on_hit-gated .on_tap/.on_pointer, and .repaint_key for paint-only dirtying driven by data outside the ordinary View diff).
CheckboxView: A declarative checkbox. See the module docs.
ChildKey: A stable identity for a list child, so a container’s reconciliation can match a child to its live widget by key across reorders/inserts instead of by position — the difference between “the third row’s widget” and “row #42’s widget” when the list is shuffled.
Clamping: Android’s scroll feel — Flutter’s ClampingScrollPhysics: a drag never leaves the range (the excess is rejected outright, for the surface to show as a stretch or a glow instead), and a release runs Android’s own SplineOverScroller deceleration to a hard stop.
ColorScheme: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
ComponentView: The View adapter that hosts a Component in any surrounding view tree.
ContainerView: A declarative decorated box. See the module docs.
ContainerWidget: The retained widget for a ContainerView. See the module docs.
CosmeticLoopRate: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
DeepLink: The deep-link read surface (frust-reactive’s app_links- style process-wide source — see its module docs for the semantics): a mobile shell delivers a platform link via frust-reactive’s push_deep_link, and app code reads it here — deep_links() returns a DeepLinks snapshot (DeepLinks::initial) plus the live, trackable DeepLinks::latest signal a Component::build reads to react to cold-start and subsequent links uniformly. Router auto-wiring (resolving deep_links() against a Router) is a separate opt-in, not automatic here.
DeepLinks: The deep-link read surface (frust-reactive’s app_links- style process-wide source — see its module docs for the semantics): a mobile shell delivers a platform link via frust-reactive’s push_deep_link, and app code reads it here — deep_links() returns a DeepLinks snapshot (DeepLinks::initial) plus the live, trackable DeepLinks::latest signal a Component::build reads to react to cold-start and subsequent links uniformly. Router auto-wiring (resolving deep_links() against a Router) is a separate opt-in, not automatic here.
DesktopConfig: The desktop app’s identity and native-integration vocabulary, re-exported from the desktop core so app code never names a shell crate: DesktopConfig (the whole declaration — app name, reverse-DNS id, window icon, menu bar, last-window-close policy — handed to App::desktop, run_desktop_config or app!’s desktop = { .. } argument), MenuSpec/MenuItemSpec/MenuRole (the platform-independent native menu tree a per-OS shell translates into an NSApp menu bar or an HMENU), DesktopIconData (decoded, tightly-packed RGBA8 — decoding a PNG/ICO/ICNS is the caller’s job), and DEFAULT_APP_NAME (the window title a config that names nothing still gets).
DesktopIconData: The desktop app’s identity and native-integration vocabulary, re-exported from the desktop core so app code never names a shell crate: DesktopConfig (the whole declaration — app name, reverse-DNS id, window icon, menu bar, last-window-close policy — handed to App::desktop, run_desktop_config or app!’s desktop = { .. } argument), MenuSpec/MenuItemSpec/MenuRole (the platform-independent native menu tree a per-OS shell translates into an NSApp menu bar or an HMENU), DesktopIconData (decoded, tightly-packed RGBA8 — decoding a PNG/ICO/ICNS is the caller’s job), and DEFAULT_APP_NAME (the window title a config that names nothing still gets).
DividerView: A declarative hairline separator. See the module docs.
DividerWidget: The retained widget for a DividerView. See the module docs.
EasingSet: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
EdgeInsets: Per-edge inset amounts, in logical pixels.
Elevation: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
ElevationLevel: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
FlexChild: One child of a FlexView: an erased child view, its flex factor (0 = inflexible; > 0 = takes a proportional share of the free main space), and an optional ChildKey for keyed reconciliation.
FlexView: A declarative flex container. See the module docs.
FontFace: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
FrameTime: The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. A point in time supplied by the shell, in monotonic nanoseconds.
GestureDetectorView: A declarative gesture wrapper. See the module docs.
GlassFill: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
GlassMaterial: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
GlassScale: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
HeroView: A declarative shared-element wrapper. See the module docs.
IconButtonView: A declarative pressable vector icon. See the module docs.
IconData: A cheap-clone handle around an icon’s path data and its design box.
IconSource: A generated icon: SVG path d data plus the side length of its square design box.
IconView: A declarative icon. See the module docs.
IconWidget: The retained widget for an IconView.
ImageError: Error decoding image bytes via ImageSource::decode.
ImageSource: A decode-once, cheaply-clonable handle around a decoded RGBA8 image.
ImageView: A declarative description of an image.
ListView: A declarative, virtualized vertical list. See the module docs.
ListViewWidget: The retained widget for a ListView: the materialized window of children (children[j] renders item keys[j]), the scroll offset + cached viewport, and the same fling bookkeeping as crate::ScrollWidget.
Location: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
Memo: A memo is an efficient derived reactive value based on other reactive values.
MenuEvent: The menu-activation read surface (frust-reactive’s process-wide menu source — see its module docs): a per-OS desktop shell drains its native menu queue once per frame and reports each activation, and app code observes it here. menu_events() returns the live MenuEvents handle whose latest signal carries a MenuEvent — the activated item’s id exactly as the app wrote it in its MenuSpec, plus a monotonic sequence so choosing the same item twice reads as two activations rather than one stale value.
MenuEvents: The menu-activation read surface (frust-reactive’s process-wide menu source — see its module docs): a per-OS desktop shell drains its native menu queue once per frame and reports each activation, and app code observes it here. menu_events() returns the live MenuEvents handle whose latest signal carries a MenuEvent — the activated item’s id exactly as the app wrote it in its MenuSpec, plus a monotonic sequence so choosing the same item twice reads as two activations rather than one stale value.
MenuSpec: The desktop app’s identity and native-integration vocabulary, re-exported from the desktop core so app code never names a shell crate: DesktopConfig (the whole declaration — app name, reverse-DNS id, window icon, menu bar, last-window-close policy — handed to App::desktop, run_desktop_config or app!’s desktop = { .. } argument), MenuSpec/MenuItemSpec/MenuRole (the platform-independent native menu tree a per-OS shell translates into an NSApp menu bar or an HMENU), DesktopIconData (decoded, tightly-packed RGBA8 — decoding a PNG/ICO/ICNS is the caller’s job), and DEFAULT_APP_NAME (the window title a config that names nothing still gets).
MotionDurations: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
MotionScheme: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
MotionSpring: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
NativeTypefaces: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
NavigatorController: The app-state handle to a navigator: a cloneable op queue an app keeps in its Component::State and drives with push/pop/ replace. Every clone shares one queue (Rc), so the handle the view carries and the handle event handlers call are the same.
NavigatorId: An opaque identity for the navigator a NavigatorController drives: every clone of one controller reports the same value, and two independently constructed controllers never do.
NavigatorView: A declarative navigator. See the module docs.
NeverScrollable: Flutter’s NeverScrollableScrollPhysics: refuse every drag, deferring everything else to the chained parent — an inner list inside an outer scroller, or a temporarily locked surface.
OverlayPlacement: A resolved placement request: which side, how it lines up, how far off the anchor it sits, and how it may move to stay inside the area.
OverlayPortalView: A declarative overlay portal. See overlay_portal.
PaddingView: A declarative padding container. See the module docs.
PanZoomController: A pan/zoom viewport over one child — a node-and-edge graph, a map, a large image — without hand-rolling the gesture math. pan_zoom lays its child out at its natural size and places it under a scale-then-translate transform (PanZoomTransform) the user drives: primary drag pans (unless the child claims the press), a touch pinch or a desktop ctrl/⌘+wheel and trackpad pinch zooms about the gesture’s focal point, clamped to .min_scale/.max_scale. A plain wheel still reaches the child, and the child sees its own unscaled local coordinates at any zoom. Flat-re-exported from frust-widgets so app code never names that crate directly; see PanZoomView’s own doc for the full contract (.inertia glide, .on_transform notification, and the PanZoomController handle’s jump_to/fit_to_bounds/fit_rect).
PanZoomTransform: A pan/zoom viewport over one child — a node-and-edge graph, a map, a large image — without hand-rolling the gesture math. pan_zoom lays its child out at its natural size and places it under a scale-then-translate transform (PanZoomTransform) the user drives: primary drag pans (unless the child claims the press), a touch pinch or a desktop ctrl/⌘+wheel and trackpad pinch zooms about the gesture’s focal point, clamped to .min_scale/.max_scale. A plain wheel still reaches the child, and the child sees its own unscaled local coordinates at any zoom. Flat-re-exported from frust-widgets so app code never names that crate directly; see PanZoomView’s own doc for the full contract (.inertia glide, .on_transform notification, and the PanZoomController handle’s jump_to/fit_to_bounds/fit_rect).
PanZoomView: A pan/zoom viewport over one child — a node-and-edge graph, a map, a large image — without hand-rolling the gesture math. pan_zoom lays its child out at its natural size and places it under a scale-then-translate transform (PanZoomTransform) the user drives: primary drag pans (unless the child claims the press), a touch pinch or a desktop ctrl/⌘+wheel and trackpad pinch zooms about the gesture’s focal point, clamped to .min_scale/.max_scale. A plain wheel still reaches the child, and the child sees its own unscaled local coordinates at any zoom. Flat-re-exported from frust-widgets so app code never names that crate directly; see PanZoomView’s own doc for the full contract (.inertia glide, .on_transform notification, and the PanZoomController handle’s jump_to/fit_to_bounds/fit_rect).
PanZoomWidget: A pan/zoom viewport over one child — a node-and-edge graph, a map, a large image — without hand-rolling the gesture math. pan_zoom lays its child out at its natural size and places it under a scale-then-translate transform (PanZoomTransform) the user drives: primary drag pans (unless the child claims the press), a touch pinch or a desktop ctrl/⌘+wheel and trackpad pinch zooms about the gesture’s focal point, clamped to .min_scale/.max_scale. A plain wheel still reaches the child, and the child sees its own unscaled local coordinates at any zoom. Flat-re-exported from frust-widgets so app code never names that crate directly; see PanZoomView’s own doc for the full contract (.inertia glide, .on_transform notification, and the PanZoomController handle’s jump_to/fit_to_bounds/fit_rect).
PathPattern: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
PlatformViewView: Platform-view embedding (platform-views feature): reserve layout space for a native view (a map, a video player, …) composited alongside the frust surface. platform_view takes the "dev.frust.<Factory>"-style native factory name registered on each platform and returns a builder (PlatformViewView) over the params/size contract — flat-re-exported from frust-widgets so app code never names that crate directly.
PopResult: The value a pop hands back to the pusher’s ResultCallback, type-erased so a page can return any 'static payload (mirroring Flutter’s Navigator.pop(result) → push(...).then(...)).
PushOptions: Options for NavigatorController::push_with_options, carrying a pushed page’s opacity, back-press BackPolicy, optional per-op transition override, optional result callback, and (for a DismissAnimated overlay) the shared dismiss-signal cell the navigator bumps on a back request.
RadioView: A declarative radio button. See the module docs.
RadioWidget: The retained widget for a RadioView.
ReadSignal: An arena-allocated getter for a reactive signal.
ResolvedPage: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
Route: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
RouteNavigator: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
RouteObserver: The reactive route-state observable: RouteObserver is the signal face over frust_widgets’ signal-free RouteStack/NavChange — the counterpart to RouteNavigator (intent, queued requests) that reads fact (the last-published stack) instead. Construct once (typically in Component::init) and attach with observe(navigator(...)); RouterDeepLinks::routes hands out the one it wired for a router-driven navigator. See route_state’s module docs for why this bridge lives in the facade rather than frust-widgets. Reactive face of one navigator’s route stack: Copy + Send + Sync (five RwSignals and nothing else), so it rides provide_context — the navigator’s own NavigatorController/ Router never can (see frust_widgets::nav::route’s module docs for why).
RouteStack: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
Router: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
RouterDeepLinks: Router ⇄ deep-link auto-wiring: router_with_deep_links/ RouterDeepLinks resolve a Router’s start location from the process’s cold-start deep link (falling back to an app-supplied default) and keep navigating it on every subsequent warm link — see RouterDeepLinks’s doc for the precedence and dedupe contracts. This is the ONLY place in the facade that sees both frust-widgets’ Router and frust-reactive‘s deep-link source together; neither underlying crate depends on the other. Router ⇄ deep-link auto-wiring: router_with_deep_links/ RouterDeepLinks resolve a Router’s start location from the process’s cold-start deep link (falling back to an app-supplied default) and keep navigating it on every subsequent warm link — see RouterDeepLinks’s doc for the precedence and dedupe contracts. This is the ONLY place in the facade that sees both frust-widgets’ Router and frust-reactive‘s deep-link source together; neither underlying crate depends on the other. Router ⇄ deep-link auto-wiring: router_with_deep_links/ RouterDeepLinks resolve a Router’s start location from the process’s cold-start deep link (falling back to an app-supplied default) and keep navigating it on every subsequent warm link — see RouterDeepLinks’s doc for the precedence and dedupe contracts. This is the ONLY place in the facade that sees both frust-widgets’ Router and frust-reactive’s deep-link source together; neither underlying crate depends on the other. A Router wired to the process-wide deep-link source (see the module docs). Construct once with router_with_deep_links (or RouterDeepLinks::new directly) — typically from Component::init, storing the result in Component::State — then call track from every Component::build to keep navigating on subsequent warm links.
RubberBand: The iOS-style rubber-band scroll feel: a drag may pull the position past an edge, resisted by [OVERSCROLL_RESISTANCE], and nothing about a boundary is rejected. See the module docs for what the trait does not carry for this physics.
RwSignal: The reactive-programming vocabulary Component state is built on: signals, memos, and context, flat-re-exported from frust-reactive/ reactive_graph so app authors never name either crate directly. An arena-allocated signal that can be read from or written to.
SafeAreaView: A declarative safe-area container. See the module docs.
ScaffoldView: A declarative scaffold. See the module docs.
ScrollInfo: A scroll observation snapshot handed to ScrollView::on_scroll.
ScrollMetrics: A read-only snapshot of a scroll surface’s extent/position, the argument every ScrollPhysics method reasons over (Flutter’s ScrollMetrics).
ScrollView: A declarative vertical scroll surface. See the module docs.
SelectionToolbarActions: The selection-toolbar seam: the request a text field publishes when it has a selection (SelectionToolbarRequest/SelectionToolbarActions), and the knobs that decide who draws it.
SelectionToolbarRequest: The selection-toolbar seam: the request a text field publishes when it has a selection (SelectionToolbarRequest/SelectionToolbarActions), and the knobs that decide who draws it.
ShadowSpec: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
ShapeScale: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
ShieldView: Platform-view embedding (platform-views feature): reserve layout space for a native view (a map, a video player, …) composited alongside the frust surface. platform_view takes the "dev.frust.<Factory>"-style native factory name registered on each platform and returns a builder (PlatformViewView) over the params/size contract — flat-re-exported from frust-widgets so app code never names that crate directly.
SizedBoxView: A declarative fixed-size box, optionally wrapping a child. See the module docs.
SliderView: A declarative slider. See the module docs.
Spring: The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. The analytic response of a SpringDesc released from an initial displacement + velocity toward equilibrium at 0.
SpringDesc: The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. Physical parameters of a damped spring (a mass on a spring with a damper).
SpringDescription: A critically-damped-family spring’s physical parameters, feeding a Simulation built from ScrollPhysics::spring (Flutter’s SpringDescription).
StackView: A declarative z-ordered stack. See the module docs.
StatusColors: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
StatusPalette: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
TextInputView: A declarative text field, single-line by default. See the module docs.
TextView: A declarative description of a run of text.
Theme: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
ThemeBuilder: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
ThemeExtensions: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
Tolerance: The velocity/distance thresholds below which a ballistic simulation is considered settled — Flutter’s Tolerance, produced by toleranceFor.
TransitionSpec: A transition selection: which PageTransition shape, driven by which Timing. Attached per-push/replace (or defaulted at the navigator level); a pop reverses the popped page’s stored spec.
TransitionState: A snapshot of the navigator’s single in-flight page transition, published by NavigatorWidget and read through NavigatorController::transition.
Tween: The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. A begin→end interpolation over a Lerp value type.
TypeScale: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
UseTask: The heavy-work idiom: AsyncValue state, use_task (the blessed load/compute helper), UseTask handle, and spawn_blocking (the CPU-bound entry point) — Frust’s counterpart to Flutter’s compute()/FutureBuilder, with explicit cancellation on component teardown. spawn_blocking joins the existing spawn/spawn_local routing pair (async IO / UI-thread !Send / one-off CPU work). App crates need no new dependency: this is the whole heavy-work surface. See frust_reactive::task for the threading contract. The handle use_task returns: a read handle to the task’s AsyncValue<T> state plus a restart/refresh trigger.
WindowMetrics: The window’s shape, flat-re-exported from frust-core::app so app code (not just widget authors, see authoring::WindowMetrics) can recover it via use_context::<WindowMetrics>() inside Component::build — a component laying itself out around window size/scale/orientation reads this the same way it reads a Theme via use_context. Delivered as a plain value (not an RwSignal); see WindowMetrics’s own doc for the derived-Orientation and rebuild-cost notes. The window’s shape and platform-occlusion state, delivered to app code as a plain provide_context-carried value — logical size, device-pixel scale, a derived orientation, and the current WindowInsets.
WriteSignal: An arena-allocated setter for a reactive signal.

Enums§

AnimationStatus: The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. The lifecycle status of an AnimationController.
AsyncValue: The heavy-work idiom: AsyncValue state, use_task (the blessed load/compute helper), UseTask handle, and spawn_blocking (the CPU-bound entry point) — Frust’s counterpart to Flutter’s compute()/FutureBuilder, with explicit cancellation on component teardown. spawn_blocking joins the existing spawn/spawn_local routing pair (async IO / UI-thread !Send / one-off CPU work). App crates need no new dependency: this is the whole heavy-work surface. See frust_reactive::task for the threading contract. The exhaustive state of an asynchronously-loaded value.
Axis: The axis a FlexView lays its children along.
BackPolicy: How a page participates in a back press routed through NavigatorController::request_back (Android hardware/gesture back, via the facade’s back-press wiring). A page declares its policy when pushed via PushOptions::back; every existing push defaults to Pop.
BorderStyle: A border’s stroke style, set via ContainerView::border_style. Solid by default; ContainerView::border alone (with no .border_style call) keeps the pre-existing solid-only behavior unchanged.
Brightness: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
ButtonStyle: Visual style variant for Button. Additive: the default preserves today’s only look byte-for-byte under every theme. See the module docs for the full role-mapping intent.
CrossAxisAlignment: How children are aligned along the cross axis.
CursorIcon: The pointer-cursor vocabulary, flat-re-exported from frust-core::event (and also available through authoring::CursorIcon).
Curve: The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. An easing curve mapping a normalized time t ∈ [0, 1] to an eased progress ∈ [0, 1].
DecelerationRate: How quickly a Bouncing surface’s fling decays — Flutter’s ScrollDecelerationRate.
DesignLanguage: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
EditCommand: The clipboard/selection command vocabulary, flat-re-exported from frust-core::event (and also available through authoring::EditCommand).
ImageDecodeError: Off-thread image decode: decode_image_async wraps the existing synchronous ImageSource::decode in spawn_blocking, so it composes with use_task for the full load/error/ready idiom without ever blocking the UI thread on a decode. See image_async’s module docs for why this lives in the facade rather than frust-widgets (which stays reactive-free by charter) and for the Arc-move contract the decoded ImageSource crosses threads under. Off-thread image decode: decode_image_async wraps the existing synchronous ImageSource::decode in spawn_blocking, so it composes with use_task for the full load/error/ready idiom without ever blocking the UI thread on a decode. See image_async’s module docs for why this lives in the facade rather than frust-widgets (which stays reactive-free by charter) and for the Arc-move contract the decoded ImageSource crosses threads under. Off-thread image decode: decode_image_async wraps the existing synchronous ImageSource::decode in spawn_blocking, so it composes with use_task for the full load/error/ready idiom without ever blocking the UI thread on a decode. See image_async’s module docs for why this lives in the facade rather than frust-widgets (which stays reactive-free by charter) and for the Arc-move contract the decoded ImageSource crosses threads under. The error decode_image_async can fail with.
ImageFit: How an Image’s laid-out box relates to its source’s natural pixel size at paint time.
MainAxisAlignment: How children are distributed along the main axis.
MenuItemSpec: The desktop app’s identity and native-integration vocabulary, re-exported from the desktop core so app code never names a shell crate: DesktopConfig (the whole declaration — app name, reverse-DNS id, window icon, menu bar, last-window-close policy — handed to App::desktop, run_desktop_config or app!’s desktop = { .. } argument), MenuSpec/MenuItemSpec/MenuRole (the platform-independent native menu tree a per-OS shell translates into an NSApp menu bar or an HMENU), DesktopIconData (decoded, tightly-packed RGBA8 — decoding a PNG/ICO/ICNS is the caller’s job), and DEFAULT_APP_NAME (the window title a config that names nothing still gets).
MenuRole: The desktop app’s identity and native-integration vocabulary, re-exported from the desktop core so app code never names a shell crate: DesktopConfig (the whole declaration — app name, reverse-DNS id, window icon, menu bar, last-window-close policy — handed to App::desktop, run_desktop_config or app!’s desktop = { .. } argument), MenuSpec/MenuItemSpec/MenuRole (the platform-independent native menu tree a per-OS shell translates into an NSApp menu bar or an HMENU), DesktopIconData (decoded, tightly-packed RGBA8 — decoding a PNG/ICO/ICNS is the caller’s job), and DEFAULT_APP_NAME (the window title a config that names nothing still gets).
NavChange: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
NavRequest: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
Orientation: The window’s shape, flat-re-exported from frust-core::app so app code (not just widget authors, see authoring::WindowMetrics) can recover it via use_context::<WindowMetrics>() inside Component::build — a component laying itself out around window size/scale/orientation reads this the same way it reads a Theme via use_context. Delivered as a plain value (not an RwSignal); see WindowMetrics’s own doc for the derived-Orientation and rebuild-cost notes. A window’s derived portrait/landscape orientation.
OutsideTap: The overlay portal’s own vocabulary, flat-re-exported from frust-core: which z-band a floated surface sits in, whether the pointer reaches it, and what a press landing outside it delivers.
OverlayAlign: How a floated surface lines up with its anchor on the cross axis.
OverlayBand: The overlay portal’s own vocabulary, flat-re-exported from frust-core: which z-band a floated surface sits in, whether the pointer reaches it, and what a press landing outside it delivers.
OverlayInput: The overlay portal’s own vocabulary, flat-re-exported from frust-core: which z-band a floated surface sits in, whether the pointer reaches it, and what a press landing outside it delivers.
OverlaySide: The side of the anchor a floated surface opens on.
OverscrollEffect: How overscroll displacement/pull is VISUALIZED — orthogonal to physics.
PageTransition: The visual shape of a page transition. The navigator maps the active transition’s progress onto per-page geometry through resolve_layers.
PageVisibility: Where a retained page sits in the stack right now — the vocabulary PushOptions::on_visibility/NavigatorView::on_root_visibility report.
Resolution: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
ResolvedSurfaceMode: App-facing resolved surface mode — the read-only outward half of the Mode B seam whose setter is deliberately absent (see the comment above): what the platform actually gave this process, not what the host asked for.
SelectionToolbarPolicy: The selection-toolbar seam: the request a text field publishes when it has a selection (SelectionToolbarRequest/SelectionToolbarActions), and the knobs that decide who draws it.
SurfaceRole: The design-token vocabulary: the Theme bundle plus its component token tables, flat-re-exported from frust-theme so app code never names that crate directly. A root component reads the active theme via use_context::<Theme>(); a widget reads it during paint/layout via PaintCtx::theme_as/LayoutCtx::theme_as (or Theme::from_paint_ctx).
SystemUiMode: App-facing system-UI (system-bar) override: set_system_ui_mode requests a status-/navigation-bar visibility mode — the Flutter SystemChrome.setEnabledSystemUIMode analog — reaching whichever shell is running the next time it polls (once per frame, mirroring set_app_theme’s delivery timing). See frust_shell_common::system_ui’s module docs for the full layering rationale, the thread contract (a plain Mutex-guarded process-global, callable from any thread), the FFI wire format each mobile shell exports, and where Android/iOS diverge from the five-mode vocabulary.
SystemUiOverlay: App-facing system-UI (system-bar) override: set_system_ui_mode requests a status-/navigation-bar visibility mode — the Flutter SystemChrome.setEnabledSystemUIMode analog — reaching whichever shell is running the next time it polls (once per frame, mirroring set_app_theme’s delivery timing). See frust_shell_common::system_ui’s module docs for the full layering rationale, the thread contract (a plain Mutex-guarded process-global, callable from any thread), the FFI wire format each mobile shell exports, and where Android/iOS diverge from the five-mode vocabulary.
Timing: How a transition’s 0.0..=1.0 progress is driven.
TransitionDriver: The page-transition resolve/drive path: the framework’s own reduce- motion collapse policy, re-exported so an app-authored animation reuses it rather than re-deriving it.

Constants§

DEFAULT_APP_NAME: The desktop app’s identity and native-integration vocabulary, re-exported from the desktop core so app code never names a shell crate: DesktopConfig (the whole declaration — app name, reverse-DNS id, window icon, menu bar, last-window-close policy — handed to App::desktop, run_desktop_config or app!’s desktop = { .. } argument), MenuSpec/MenuItemSpec/MenuRole (the platform-independent native menu tree a per-OS shell translates into an NSApp menu bar or an HMENU), DesktopIconData (decoded, tightly-packed RGBA8 — decoding a PNG/ICO/ICNS is the caller’s job), and DEFAULT_APP_NAME (the window title a config that names nothing still gets).
DEFAULT_REDIRECT_LIMIT: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
MAX_FLING_VELOCITY: The fastest fling speed (px/s) a physics honors — Flutter’s kMaxFlingVelocity. A release faster than this clamps to it.
MIN_FLING_VELOCITY: The minimum release speed (px/s) that starts a fling — Flutter’s kMinFlingVelocity. A release slower than this is treated as a plain drag-end, never a fling.

Traits§

Component: A piece of UI with retained local state (Flutter’s StatefulWidget analog).
Get: Clones the value of the signal, without tracking the value reactively. and subscribes the active reactive observer (an effect or computed) to changes in its value.
GetUntracked: Clones the value of the signal, without tracking the value reactively.
Lerp: The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. Component-wise linear interpolation between two values of the same type.
ScrollPhysics: A pluggable scroll-motion strategy — Flutter’s ScrollPhysics contract.
Set: Updates the value of the signal by replacing it.
Simulation: A ballistic motion curve over time, produced by ScrollPhysics::create_ballistic_simulation and driven by the consuming widget after a gesture release (fling decay, a spring-back, or any other closed-form or iterative curve).
Track: Allows tracking the value of some reactive data.
Update: Updates the value of a signal by applying a function that updates it in place, notifying its subscribers that the value has changed.
View: A declarative description of a piece of UI.
With: Give read-only access to a signal’s value by reference inside a closure, and subscribes the active reactive observer (an effect or computed) to changes in its value.
WithUntracked: Give read-only access to a signal’s value by reference inside a closure, without tracking the value reactively.

Functions§

Align: Position child within the align’s box per alignment.
Button: PascalCase alias for button, matching the container view-fn vocabulary.
Checkbox: PascalCase alias for checkbox.
Column: A vertical flex (Axis::Vertical) of inflexible children — the common sugar. Use FlexView::new with flexible children when some should expand.
GestureDetector: Wrap child in a gesture detector (no recognisers until one is attached, e.g. with GestureDetectorView::on_tap or GestureDetectorView::on_long_press).
Icon: PascalCase alias for icon.
IconButton: PascalCase alias for icon_button, matching the container view-fn vocabulary (see crate::Icon/crate::Button’s own aliases).
Image: Create an image view over a decoded ImageSource, defaulting to ImageFit::Contain.
Padding: Inset child by insets on each edge.
Radio: PascalCase alias for radio.
Row: A horizontal flex (Axis::Horizontal) of inflexible children — the common sugar. Use FlexView::new with flexible children when some should expand.
SizedBox: A box that forces width/height where Some, passing through where None.
Slider: PascalCase alias for slider.
Stack: Overlay children in a z-order stack (first child at the bottom).
TextInput: PascalCase alias for text_input.
any: Erase view into an AnyView — the free-function spelling of AnyView::new, mirroring the text(..)/button(..) view-fn vocabulary.
attach_back_handler: Android back-press ⇄ navigator auto-wiring: attach_back_handler/BackHandler pop a NavigatorController on a platform back press and keep frust-reactive‘s handles_back flag in sync with the stack depth, so a shell knows whether a root-level back should fall through to the platform (activity finish). Mirrors RouterDeepLinks’s shape and, like it, is the ONLY place in the facade that sees both frust-widgets’ NavigatorController and frust-reactive’s back-press source together — see BackHandler’s doc for the consume/dedupe and timing contracts. Call BackHandler::track from every Component::build. Android back-press ⇄ navigator auto-wiring: attach_back_handler/BackHandler pop a NavigatorController on a platform back press and keep frust-reactive‘s handles_back flag in sync with the stack depth, so a shell knows whether a root-level back should fall through to the platform (activity finish). Mirrors RouterDeepLinks’s shape and, like it, is the ONLY place in the facade that sees both frust-widgets’ NavigatorController and frust-reactive’s back-press source together — see BackHandler’s doc for the consume/dedupe and timing contracts. Call BackHandler::track from every Component::build. Android back-press ⇄ navigator auto-wiring: attach_back_handler/BackHandler pop a NavigatorController on a platform back press and keep frust-reactive‘s handles_back flag in sync with the stack depth, so a shell knows whether a root-level back should fall through to the platform (activity finish). Mirrors RouterDeepLinks’s shape and, like it, is the ONLY place in the facade that sees both frust-widgets’ NavigatorController and frust-reactive’s back-press source together — see BackHandler’s doc for the consume/dedupe and timing contracts. Call BackHandler::track from every Component::build. Convenience constructor equivalent to BackHandler::new — see its docs and RouterDeepLinks/router_with_deep_links for the mirrored API shape.
back_presses: The Android back-press source (frust-reactive’s process-wide back source — see its back module docs). A mobile shell delivers a hardware/gesture back press via push_back_press, and the facade’s BackHandler reads it via back_presses to pop a navigator; set_handles_back/handles_back are the “framework consumes the next back” flag a shell polls to decide whether a root-level back falls through to the platform. App code normally uses attach_back_handler rather than these directly; push_back_press is also the desktop dev seam (no shell writes on desktop yet). The current back-press read surface: the live BackPresses::count signal. Call from a tracked context (e.g. inside Component::build, via the facade’s BackHandler) to observe subsequent presses as they arrive.
button: Create a button labelled label that runs on_press against the app state when released inside its bounds.
canvas: Declarative custom painting over the [PaintScene] trait object — a chart, a node-and-edge graph, a game board — without hand-rolling a View/ Widget pair. canvas takes a paint closure that runs in local space (the widget’s own top-left is always (0, 0), and painting past its own size is clipped, never a bug to chase) — flat-re-exported from frust-widgets so app code never names that crate directly. See CanvasView’s own doc for the full builder contract (.size/.expand sizing, .on_hit-gated .on_tap/.on_pointer, and .repaint_key for paint-only dirtying driven by data outside the ordinary View diff).
checkbox: Create a checkbox reflecting checked, labelled label, that fires on_toggle(state, !checked) on release inside its bounds.
clear_app_theme: App-facing theme override: set_app_theme forces the app’s active Theme end-to-end — both delivery paths a shell owned exclusively before this (widget paint/layout via RenderRoot::set_theme, and use_context::<Theme>() via provide_context) — reflecting the change the next time the running shell polls (once per frame; desktop before rebuild, mobile at the top of the frame callback). clear_app_theme returns to the platform’s own light/dark-derived default. See frust_shell_common::theme_override’s module docs for the full layering rationale, the thread contract (a plain Mutex-guarded process-global — no UI-thread panic, unlike push_deep_link), and the override-wins-over-appearance rule (an app override, once set, is never overridden back by a live platform dark-mode flip until clear_app_theme runs).
colored_box: A childless ContainerView — the leaf/background family. See the module docs.
component: Host a Component as a View — the view-fn spelling of ComponentView, mirroring the text(..)/button(..) vocabulary.
container: Wrap child in a ContainerView — the single-child wrapper family. See the module docs.
decode_image_async: Off-thread image decode: decode_image_async wraps the existing synchronous ImageSource::decode in spawn_blocking, so it composes with use_task for the full load/error/ready idiom without ever blocking the UI thread on a decode. See image_async’s module docs for why this lives in the facade rather than frust-widgets (which stays reactive-free by charter) and for the Arc-move contract the decoded ImageSource crosses threads under. Off-thread image decode: decode_image_async wraps the existing synchronous ImageSource::decode in spawn_blocking, so it composes with use_task for the full load/error/ready idiom without ever blocking the UI thread on a decode. See image_async’s module docs for why this lives in the facade rather than frust-widgets (which stays reactive-free by charter) and for the Arc-move contract the decoded ImageSource crosses threads under. Off-thread image decode: decode_image_async wraps the existing synchronous ImageSource::decode in spawn_blocking, so it composes with use_task for the full load/error/ready idiom without ever blocking the UI thread on a decode. See image_async’s module docs for why this lives in the facade rather than frust-widgets (which stays reactive-free by charter) and for the Arc-move contract the decoded ImageSource crosses threads under. Decodes PNG/JPEG bytes off the UI thread via frust_reactive::spawn_blocking, returning the same ImageSource ImageSource::decode would build synchronously.
deep_links: The deep-link read surface (frust-reactive’s app_links- style process-wide source — see its module docs for the semantics): a mobile shell delivers a platform link via frust-reactive’s push_deep_link, and app code reads it here — deep_links() returns a DeepLinks snapshot (DeepLinks::initial) plus the live, trackable DeepLinks::latest signal a Component::build reads to react to cold-start and subsequent links uniformly. Router auto-wiring (resolving deep_links() against a Router) is a separate opt-in, not automatic here.
divider: A horizontal hairline of color, [DEFAULT_THICKNESS] (1px) thick, filling the available width. color is a required argument, not defaulted — see the module docs’ “Color: required, no Theme dependency” section.
flexible: A flexible child taking flex proportional shares of the free main-axis space.
handles_back: The Android back-press source (frust-reactive’s process-wide back source — see its back module docs). A mobile shell delivers a hardware/gesture back press via push_back_press, and the facade’s BackHandler reads it via back_presses to pop a navigator; set_handles_back/handles_back are the “framework consumes the next back” flag a shell polls to decide whether a root-level back falls through to the platform. App code normally uses attach_back_handler rather than these directly; push_back_press is also the desktop dev seam (no shell writes on desktop yet). Whether the framework wants to consume the next back press. A shell polls this to decide whether a back press should be routed into the app (true) or fall through to the platform / activity finish (false, the default until glue publishes otherwise — see the module docs).
hero: Tag child as a shared element under tag, so a navigator morphs it between two pages that both carry the same tag during a page transition. Outside a transition this is a transparent wrapper.
icon: Create an icon view over any IconData source (a generated IconSource, or a user path via IconData::from_path), at the default 24.0 logical size with the theme’s on_surface color.
icon_button: Create a pressable vector icon painting mark, labelled label for accessibility, that runs on_press against the app state when released inside its bounds. See the module docs.
inflexible: An inflexible child, sized to its natural main-axis extent.
keyed: An inflexible child tagged with a stable ChildKey, for a list whose items reorder, insert, or delete between frames.
list_view: Create a virtualized ListView — the free-function spelling of ListView::builder.
lock_selection_toolbar_policy: The selection-toolbar seam: the request a text field publishes when it has a selection (SelectionToolbarRequest/SelectionToolbarActions), and the knobs that decide who draws it.
make_driver: The page-transition resolve/drive path: the framework’s own reduce- motion collapse policy, re-exported so an app-authored animation reuses it rather than re-deriving it.
menu_events: The menu-activation read surface (frust-reactive’s process-wide menu source — see its module docs): a per-OS desktop shell drains its native menu queue once per frame and reports each activation, and app code observes it here. menu_events() returns the live MenuEvents handle whose latest signal carries a MenuEvent — the activated item’s id exactly as the app wrote it in its MenuSpec, plus a monotonic sequence so choosing the same item twice reads as two activations rather than one stale value.
navigator: Build a NavigatorView driven by controller — the facade’s back-aware wrapper over frust_widgets::navigator.
on_cleanup: The reactive-programming vocabulary Component state is built on: signals, memos, and context, flat-re-exported from frust-reactive/ reactive_graph so app authors never name either crate directly. Registers a function to be run the next time the current owner is cleaned up.
overlay_host: Build a root overlay host driven by controller, wrapping the app’s whole root view — the facade’s back-aware wrapper over frust_widgets::overlay_host.
overlay_portal: Float overlay above the whole app, anchored to child’s bounds — the declarative half of the portal.
pan_zoom: A pan/zoom viewport over one child — a node-and-edge graph, a map, a large image — without hand-rolling the gesture math. pan_zoom lays its child out at its natural size and places it under a scale-then-translate transform (PanZoomTransform) the user drives: primary drag pans (unless the child claims the press), a touch pinch or a desktop ctrl/⌘+wheel and trackpad pinch zooms about the gesture’s focal point, clamped to .min_scale/.max_scale. A plain wheel still reaches the child, and the child sees its own unscaled local coordinates at any zoom. Flat-re-exported from frust-widgets so app code never names that crate directly; see PanZoomView’s own doc for the full contract (.inertia glide, .on_transform notification, and the PanZoomController handle’s jump_to/fit_to_bounds/fit_rect).
platform_view: Platform-view embedding (platform-views feature): reserve layout space for a native view (a map, a video player, …) composited alongside the frust surface. platform_view takes the "dev.frust.<Factory>"-style native factory name registered on each platform and returns a builder (PlatformViewView) over the params/size contract — flat-re-exported from frust-widgets so app code never names that crate directly.
provide_context: The reactive-programming vocabulary Component state is built on: signals, memos, and context, flat-re-exported from frust-reactive/ reactive_graph so app authors never name either crate directly. Provides a context value of type T to the current reactive Owner and all of its descendants. This can be accessed using use_context.
push_back_press: The Android back-press source (frust-reactive’s process-wide back source — see its back module docs). A mobile shell delivers a hardware/gesture back press via push_back_press, and the facade’s BackHandler reads it via back_presses to pop a navigator; set_handles_back/handles_back are the “framework consumes the next back” flag a shell polls to decide whether a root-level back falls through to the platform. App code normally uses attach_back_handler rather than these directly; push_back_press is also the desktop dev seam (no shell writes on desktop yet). Deliver a platform back press into the process-wide source. Called by a shell (the Android back callback) on the UI thread; app code never calls this directly.
push_deep_link: The deep-link read surface (frust-reactive’s app_links- style process-wide source — see its module docs for the semantics): a mobile shell delivers a platform link via frust-reactive’s push_deep_link, and app code reads it here — deep_links() returns a DeepLinks snapshot (DeepLinks::initial) plus the live, trackable DeepLinks::latest signal a Component::build reads to react to cold-start and subsequent links uniformly. Router auto-wiring (resolving deep_links() against a Router) is a separate opt-in, not automatic here.
radio: Create a radio reflecting selected, labelled label. Attach a callback with RadioView::on_select; a radio with none is inert (still paints and captures the press, but never fires) — the same optional-callback shape a design system’s own list-item row uses.
register_app_fonts: App-facing pending-font registry: register_app_fonts pushes raw font bytes (TTF/OTF, or a TTC/OTC collection) to be registered into the running shell’s TextContext the next time it drains this registry (construction time, and once per frame – each shell’s own wiring). See frust_shell_common::font_registry’s module docs for the full layering rationale and thread contract (mirrors set_app_theme’s: a plain Mutex-guarded process-global, callable from any thread).
resolve_spec: The page-transition resolve/drive path: the framework’s own reduce- motion collapse policy, re-exported so an app-authored animation reuses it rather than re-deriving it.
resolved_surface_mode: App-facing resolved surface mode — the read-only outward half of the Mode B seam whose setter is deliberately absent (see the comment above): what the platform actually gave this process, not what the host asked for.
router_with_deep_links: Router ⇄ deep-link auto-wiring: router_with_deep_links/ RouterDeepLinks resolve a Router’s start location from the process’s cold-start deep link (falling back to an app-supplied default) and keep navigating it on every subsequent warm link — see RouterDeepLinks’s doc for the precedence and dedupe contracts. This is the ONLY place in the facade that sees both frust-widgets’ Router and frust-reactive‘s deep-link source together; neither underlying crate depends on the other. Router ⇄ deep-link auto-wiring: router_with_deep_links/ RouterDeepLinks resolve a Router’s start location from the process’s cold-start deep link (falling back to an app-supplied default) and keep navigating it on every subsequent warm link — see RouterDeepLinks’s doc for the precedence and dedupe contracts. This is the ONLY place in the facade that sees both frust-widgets’ Router and frust-reactive‘s deep-link source together; neither underlying crate depends on the other. Router ⇄ deep-link auto-wiring: router_with_deep_links/ RouterDeepLinks resolve a Router’s start location from the process’s cold-start deep link (falling back to an app-supplied default) and keep navigating it on every subsequent warm link — see RouterDeepLinks’s doc for the precedence and dedupe contracts. This is the ONLY place in the facade that sees both frust-widgets’ Router and frust-reactive’s deep-link source together; neither underlying crate depends on the other. Convenience constructor equivalent to RouterDeepLinks::new — see its docs for the precedence rule and the call-once contract.
run: Run a root Component in the desktop preview shell until the window closes — the canonical runApp equivalent for the Component model.
run_desktop_config: run with the app’s desktop identity (DesktopConfig) — the no-setup half of the config-carrying pair, and the function app!’s desktop = { .. } argument routes through when no setup = { .. } block accompanies it.
run_with_setup: run with a setup closure run once, immediately before root.init() — the desktop half of app!’s setup = { .. } block.
run_with_setup_and_config: run_with_setup and run_desktop_config at once: the single desktop entry point the other three delegate to, differing only in which of setup and config they default.
safe_area: Pad child by the window’s resolved safe-area insets — all four edges enabled by default (opt an edge out with .left/.top/.right/.bottom), never less than .minimum (zero by default) on an enabled edge. The enabled edges’ insets are consumed: child’s subtree reads zero safe-area padding there (see the module docs).
scaffold: Scaffold body under no chrome — attach app_bar/bottom_bar/fab with the builder methods below.
scroll_view: Wrap child in a vertical ScrollView — the free-function spelling of ScrollView::new.
set_app_theme: App-facing theme override: set_app_theme forces the app’s active Theme end-to-end — both delivery paths a shell owned exclusively before this (widget paint/layout via RenderRoot::set_theme, and use_context::<Theme>() via provide_context) — reflecting the change the next time the running shell polls (once per frame; desktop before rebuild, mobile at the top of the frame callback). clear_app_theme returns to the platform’s own light/dark-derived default. See frust_shell_common::theme_override’s module docs for the full layering rationale, the thread contract (a plain Mutex-guarded process-global — no UI-thread panic, unlike push_deep_link), and the override-wins-over-appearance rule (an app override, once set, is never overridden back by a live platform dark-mode flip until clear_app_theme runs).
set_default_theme: Design-system-facing base-theme seed: set_default_theme supplies the starting theme a shell seeds itself with, in place of its own built-in fallback — the seam a design-system plugin’s install() calls. Unlike set_app_theme, this does NOT pin brightness: the shell keeps re-deriving light/dark from the platform’s own appearance against this same base, so a design-system-themed app installed this way still honours system dark mode. See frust_shell_common::theme_default’s module docs for the full precedence order (set_app_theme override → set_default_theme base → the shell’s built-in fallback) and the brightness-following contrast with set_app_theme spelled out in full.
set_handles_back: The Android back-press source (frust-reactive‘s process-wide back source — see its back module docs). A mobile shell delivers a hardware/gesture back press via push_back_press, and the facade’s BackHandler reads it via back_presses to pop a navigator; set_handles_back/handles_back are the “framework consumes the next back” flag a shell polls to decide whether a root-level back falls through to the platform. App code normally uses attach_back_handler rather than these directly; push_back_press is also the desktop dev seam (no shell writes on desktop yet). Publish whether the framework will consume the next back press (see the module docs’ handles_back section). The facade’s BackHandler calls this each rebuild with controller.can_pop(); a shell reads the answer via handles_back.
set_selection_toolbar_builder: The selection-toolbar seam: the request a text field publishes when it has a selection (SelectionToolbarRequest/SelectionToolbarActions), and the knobs that decide who draws it.
set_selection_toolbar_policy: The selection-toolbar seam: the request a text field publishes when it has a selection (SelectionToolbarRequest/SelectionToolbarActions), and the knobs that decide who draws it.
set_system_ui_mode: App-facing system-UI (system-bar) override: set_system_ui_mode requests a status-/navigation-bar visibility mode — the Flutter SystemChrome.setEnabledSystemUIMode analog — reaching whichever shell is running the next time it polls (once per frame, mirroring set_app_theme’s delivery timing). See frust_shell_common::system_ui’s module docs for the full layering rationale, the thread contract (a plain Mutex-guarded process-global, callable from any thread), the FFI wire format each mobile shell exports, and where Android/iOS diverge from the five-mode vocabulary.
shell_route: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
shield: Platform-view embedding (platform-views feature): reserve layout space for a native view (a map, a video player, …) composited alongside the frust surface. platform_view takes the "dev.frust.<Factory>"-style native factory name registered on each platform and returns a builder (PlatformViewView) over the params/size contract — flat-re-exported from frust-widgets so app code never names that crate directly.
signal: Creates an arena-allocated signal, the basic reactive primitive.
slider: Create a slider at value (clamped to 0.0..=1.0) that fires on_change(state, new_value) as it is dragged.
spawn: Spawns a Send future on the background reactive runtime (Tokio-backed — see frust_reactive::ReactiveRuntime). A thin wrapper over any_spawner::Executor::spawn; app authors never name any_spawner.
spawn_blocking: The heavy-work idiom: AsyncValue state, use_task (the blessed load/compute helper), UseTask handle, and spawn_blocking (the CPU-bound entry point) — Frust’s counterpart to Flutter’s compute()/FutureBuilder, with explicit cancellation on component teardown. spawn_blocking joins the existing spawn/spawn_local routing pair (async IO / UI-thread !Send / one-off CPU work). App crates need no new dependency: this is the whole heavy-work surface. See frust_reactive::task for the threading contract. Runs a one-off, blocking CPU workload on the background runtime’s blocking thread pool, returning a JoinHandle to .await its result.
spawn_local: Spawns a !Send future on the UI-thread local task queue, drained each frame by the shell (ReactiveRuntime::pump_local). A thin wrapper over any_spawner::Executor::spawn_local; must be called on the UI thread — see frust_reactive::ReactiveRuntime::pump_local’s doc for the panic this triggers off-thread.
text: Create a text view rendering content with default styling (16px). Its glyph color defaults to the active theme’s on_surface role, falling back to black when no theme is set; an explicit TextView::color overrides both.
text_input: Create a controlled text field showing value that fires on_change(state, new_text) on every edit.
use_context: The reactive-programming vocabulary Component state is built on: signals, memos, and context, flat-re-exported from frust-reactive/ reactive_graph so app authors never name either crate directly. Extracts a context value of type T from the reactive system.
use_task: The heavy-work idiom: AsyncValue state, use_task (the blessed load/compute helper), UseTask handle, and spawn_blocking (the CPU-bound entry point) — Frust’s counterpart to Flutter’s compute()/FutureBuilder, with explicit cancellation on component teardown. spawn_blocking joins the existing spawn/spawn_local routing pair (async IO / UI-thread !Send / one-off CPU work). App crates need no new dependency: this is the whole heavy-work surface. See frust_reactive::task for the threading contract. Runs a fetch, wiring a heavy-work idiom around it.

Type Aliases§

Color: The color type every ColorScheme role is expressed in (peniko::Color), re-exported so app code can author its own color values (e.g. a custom accent palette that composes onto a baseline ColorScheme) without naming peniko directly — the same facade-only-dependency rule the theme re-exports above follow. Construct one with Color::from_rgb8/Color::new; read its channels via Color::components ([f32; 4], straight-alpha RGBA). A convenient alias for the color type used for Brush.
ErrorBuilder: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
NavWaker: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
PageBuilder: A page builder: a cheap closure that produces the page’s view, re-run every rebuild so a retained page’s content still reconciles against live app state (the pod, and thus the page’s internal widget state, is preserved across the rebuild — only the view descriptor is rebuilt).
Redirect: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
ResultCallback: A pusher-registered result callback: invoked with &mut State when the page it was registered against is popped, carrying the PopResult the pop supplied.
RouteBuilder: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
RouteParams: The declarative router vocabulary (a go_router-subset layer), flat-re-exported from frust-widgets so app code never names that crate directly: Router resolves a location against a Route table (built via RouteBuilder) into Resolution/ResolvedPages driving a NavigatorController, with :param/query parsing (Location/PathPattern/RouteParams), per-route/top-level Redirects (loop-guarded at DEFAULT_REDIRECT_LIMIT), and an ErrorBuilder fallback for an unmatched location.
TaskError: The heavy-work idiom: AsyncValue state, use_task (the blessed load/compute helper), UseTask handle, and spawn_blocking (the CPU-bound entry point) — Frust’s counterpart to Flutter’s compute()/FutureBuilder, with explicit cancellation on component teardown. spawn_blocking joins the existing spawn/spawn_local routing pair (async IO / UI-thread !Send / one-off CPU work). App crates need no new dependency: this is the whole heavy-work surface. See frust_reactive::task for the threading contract. The boxed error an AsyncValue::Error carries. Arc-wrapped so a clone of the state is cheap and the error is shareable across the tree.
VisibilityCallback: A page-visibility observer, registered per page via PushOptions::on_visibility (or NavigatorView::on_root_visibility for the root page). Fired by the navigator from a rebuild whenever the page’s PageVisibility changes — never twice with the same value.

Crate frust

Crate frust Copy item path

§Low-level escape hatch: App::new

§Layout containers

Re-exports§

Modules§

Macros§

Structs§

Enums§

Constants§

Traits§

Functions§

Type Aliases§

Crate frust

§Low-level escape hatch: `App::new`