JSVision

Appearance

@jsvision/ui / Switch

Class: Switch ​

Documented in: Switch

Defined in: ui/src/controls/switch.ts:70

A focusable on/off toggle bound two-way to a Signal<boolean> (see the module docs for glyphs, colours, and interaction).

Example ​

ts
import { Group, Switch, signal, createEventLoop } from '@jsvision/ui';
import { resolveCapabilities } from '@jsvision/core';

const caps = resolveCapabilities({ env: {}, platform: 'linux' }).profile;
const wifi = signal(false);
const sw = new Switch({ value: wifi, label: '~W~i-Fi', onLabel: 'On', offLabel: 'Off' });
sw.layout = { position: 'absolute', rect: { x: 0, y: 0, width: 20, height: 1 } };

const root = new Group();
root.add(sw);
const loop = createEventLoop({ width: 20, height: 1 }, { caps });
loop.mount(root);
loop.focusView(sw);
// Space/Enter, a click, or Alt+W toggles it:
wifi.set(true); // drive it externally — the knob slides right and the track turns green

Extends ​

Constructors ​

Constructor ​

new Switch(opts): Switch

Defined in: ui/src/controls/switch.ts:89

Parameters ​

opts ​

SwitchOptions

The two-way value plus an optional label/onLabel/offLabel/disabled.

Returns ​

Switch

Overrides ​

View.constructor

Properties ​

bounds ​

bounds: Rect

Defined in: ui/src/view/view.ts:65

Parent-relative integer rect; written by the layout pass — read it in draw/hit-testing.

Inherited from ​

View.bounds

castsShadow ​

castsShadow: boolean = false

Defined in: ui/src/view/view.ts:78

When true, the renderer paints a drop shadow on the cells just below and to the right of this view, in paint order (a later sibling's shadow falls over an earlier one). Default false. The Desktop sets it per window.

Inherited from ​

View.castsShadow

centered ​

centered: boolean = false

Defined in: ui/src/view/view.ts:86

When true, the layout pass recentres this view within its parent after layout — origin = (parent - self) / 2 on both axes. Intended for absolutely-placed views (a modal dialog, a message box) whose size is fixed and whose origin would otherwise be placed by the caller. Default false; Dialog sets it when centered.

Inherited from ​

View.centered

focusable ​

focusable: boolean = true

Defined in: ui/src/controls/switch.ts:72

The switch takes focus so Space/Enter toggling is scoped to it (disabled ⇒ not focusable).

Overrides ​

View.focusable

layout ​

layout: LayoutProps = {}

Defined in: ui/src/view/view.ts:69

Layout props for this view (direction, size, padding, absolute placement, …).

Inherited from ​

View.layout

offLabel ​

protected readonly offLabel: string

Defined in: ui/src/controls/switch.ts:84

onLabel ​

protected readonly onLabel: string

Defined in: ui/src/controls/switch.ts:83

Text shown when on / off (either may be '' to hide it).

parsed ​

protected readonly parsed: ParsedLabel

Defined in: ui/src/controls/switch.ts:81

The parsed caption (display text + ~X~ hotkey).

postProcess ​

postProcess: boolean = true

Defined in: ui/src/controls/switch.ts:74

Post-process so its Alt+hotkey works even when another control in the dialog holds focus.

Overrides ​

View.postProcess

preProcess ​

preProcess: boolean = false

Defined in: ui/src/view/view.ts:96

Take part in the pre-process sweep (root→down, before the focused view sees the event).

Inherited from ​

View.preProcess

raw ​

protected readonly raw: string

Defined in: ui/src/controls/switch.ts:79

The raw caption (with tildes), or '' when unlabelled.

state ​

readonly state: ViewState

Defined in: ui/src/view/view.ts:67

Draw-against flags. The object reference is fixed; individual fields mutate (e.g. focused).

Inherited from ​

View.state

value ​

protected readonly value: Signal<boolean>

Defined in: ui/src/controls/switch.ts:77

Two-way on/off value (source of truth).

Methods ​

accelerators() ​

accelerators(): readonly string[]

Defined in: ui/src/controls/switch.ts:107

The caption's ~X~ Alt-hotkey char (lowercase), for duplicate-accelerator detection; none if unmarked.

Returns ​

readonly string[]

Overrides ​

View.accelerators

bind() ​

bind<T>(reader, apply?, opts?): void

Defined in: ui/src/view/view.ts:228

Bind a reactive value to a redraw. Creates an effect (owned by this view's scope) that reads reader() — subscribing to whatever signals it touches — runs the optional apply(value), then requests a frame: a repaint by default, or a reflow when { relayout: true }. It re-runs automatically whenever those signals change, and is disposed when the view unmounts.

Call it from onMount, not the constructor — the view's scope only exists once mounted, so a pre-mount bind throws rather than silently dropping the binding.

Type Parameters ​

T ​

T

Parameters ​

reader ​

() => T

Reads the reactive source; the signals it reads become dependencies.

apply? ​

(v) => void

Optional: apply the read value to the widget (e.g. store it in a field).

opts? ​

Pass { relayout: true } when the change affects layout, so it reflows instead of just repainting.

relayout? ​

boolean

Returns ​

void

Example ​

ts
import { signal } from '@jsvision/ui';

const count = signal(0);
// `status` is a View whose draw() reads count():
status.onMount(() => {
  status.bind(() => count()); // repaint the status line whenever `count` changes
});

Inherited from ​

View.bind

derived() ​

protected derived<T>(fn): () => T

Defined in: ui/src/view/view.ts:261

Create a stable derived accessor owned by this view's scope. The returned () => T keeps the same identity for the life of the view, so it is safe to build in the constructor and hand to child views before this view mounts. The backing computed is created lazily under the view's own scope, so it is always owned and disposed at unmount — unlike a bare computed() in the constructor, which would run before any scope exists, leak, and warn.

Reads behave sensibly across the lifecycle:

  • Before mount: evaluates fn() directly (correct current value, nothing persisted). Good for a pre-mount natural-size measure.
  • After mount: builds and memoizes a computed(fn) under the view's scope.
  • After an unmount→remount: the memo is keyed to the scope it was built under, so a remounted view (which gets a fresh scope) re-derives under the new scope instead of returning the previous mount's disposed, now-frozen computed — keeping a Show/For-remounted widget reactive.

Type Parameters ​

T ​

T

Parameters ​

fn ​

() => T

The derivation (pure; the signals it reads become the computed's dependencies).

Returns ​

A stable accessor; call it to read the derived value.

() => T

Inherited from ​

View.derived

desiredCaret() ​

desiredCaret(): Point | null

Defined in: ui/src/view/view.ts:192

Where this view wants the hardware text cursor, in view-local cells, or null for no cursor (the default — most views never show one). A focused text input overrides this to place the caret at the edit position; the event loop reads it after each frame, converts it to an absolute cell, and moves the terminal cursor there.

Returns ​

Point | null

The view-local caret point (0-based, relative to this view's origin), or null.

Inherited from ​

View.desiredCaret

draw() ​

draw(ctx): void

Defined in: ui/src/controls/switch.ts:127

Paint the caption (if any), the bracketed track with the knob at its state end, and the on/off word.

Parameters ​

ctx ​

DrawContext

Returns ​

void

Overrides ​

View.draw

focusSignal() ​

focusSignal(): Signal<void>

Defined in: ui/src/view/view.ts:136

Subscribe to this view's focus changes. Reading the returned signal inside a bind/effect re-runs that effect whenever this view gains or loses focus — including from another view (e.g. a Label repainting when the control it labels is focused). The signal notifies on every poke even without a value change. Lazy: the backing signal is created on first call.

Returns ​

Signal<void>

A signal that ticks whenever this view gains or loses focus.

Example ​

ts
// Inside a widget's onMount, repaint whenever `other` view's focus changes:
this.onMount(() => this.bind(() => other.focusSignal()()));

Inherited from ​

View.focusSignal

invalidate() ​

invalidate(): void

Defined in: ui/src/view/view.ts:197

Request a repaint of this view. A no-op before the view is mounted (the first frame paints everything).

Returns ​

void

Inherited from ​

View.invalidate

invalidateLayout() ​

invalidateLayout(): void

Defined in: ui/src/view/view.ts:202

Request a reflow (re-run layout, then repaint). Use this when a change affects size/position, not just pixels.

Returns ​

void

Inherited from ​

View.invalidateLayout

measure() ​

measure(): Size2D

Defined in: ui/src/controls/switch.ts:112

Advertise the intrinsic single-row size: caption + track + on/off word.

Returns ​

Size2D

Overrides ​

View.measure

onCleanup() ​

onCleanup(fn): void

Defined in: ui/src/view/view.ts:298

Register a teardown callback that runs once when this view unmounts. Requires a mounted view — so call it from within onMount. Use it to release anything the view acquired (a timer, an external subscription).

Parameters ​

fn ​

() => void

The teardown callback.

Returns ​

void

Inherited from ​

View.onCleanup

onEvent() ​

onEvent(ev): void

Defined in: ui/src/controls/switch.ts:170

Route toggling input: Space/Enter while focused, a click anywhere on the control (focus + toggle), and the caption's Alt+hotkey from anywhere in the scope (focus + toggle). A disabled switch is inert.

Parameters ​

ev ​

DispatchEvent

The dispatch envelope (carries local/focusView during real dispatch).

Returns ​

void

Overrides ​

View.onEvent

onMount() ​

onMount(fn): void

Defined in: ui/src/view/view.ts:283

Register a callback to run once when the view becomes live (after its first layout gives it bounds). This is where to call bind, since the view's reactive scope exists by then. Registering after the view is already live runs the callback immediately.

Parameters ​

fn ​

() => void

Post-mount setup.

Returns ​

void

Inherited from ​

View.onMount

select() ​

select(on): void

Defined in: ui/src/controls/switch.ts:121

Programmatically set the on/off value (a no-op when disabled).

Parameters ​

on ​

boolean

Returns ​

void

selectByClick()? ​

optional selectByClick(): void

Defined in: ui/src/view/view.ts:182

Optional "select + raise on click" hook. Left undefined on the base, so a plain view is not a select/raise target. A container that owns z-order (a Window) overrides it to select and raise itself. The hit-test invokes the first ancestor that defines this — before delivering the mouse-down — so a click always raises the window even if the interior also consumes the click.

Returns ​

void

Inherited from ​

View.selectByClick

toggle() ​

protected toggle(): void

Defined in: ui/src/controls/switch.ts:203

Flip the bound value (the value bind repaints).

Returns ​

void