Implement Switch component.

src/components/forms/controls/Switch/Switch.module.scss

@@ -0,0 +1,63 @@
+
+@use '../../../../styling/defs.scss' as bk;
+
+/* Note: `light-dark()` does not seem to be animatable in Chrome 125, even with `@property` */
+// @property --bk-switch-track-color { syntax: '<color>'; inherits: true; initial-value: bk.$color-grey-600; }
+// @property --bk-switch-thumb-color { syntax: '<color>'; inherits: true; initial-value: bk.$color-grey-400; }
+@property --bk-switch-pos { syntax: '<length-percentage>'; inherits: true; initial-value: 50%; }
+
+@layer baklava.components {
+  .bk-switch {
+    @include bk.component-base(bk-switch);
+
+    --bk-switch-track-color: #{bk.$theme-switch-slider-off};
+    --bk-switch-thumb-color: #{bk.$theme-switch-knob-off};
+
+    --w: 34px; // Track width
+    --h: 14px; // Track height
+    --r: 10px; // Thumb radius
+    --pos-start: var(--r);
+    --pos-end: calc(100% - var(--r));
+    --bk-switch-pos: var(--pos-start);
+
+    cursor: pointer;
+
+    appearance: none;
+    height: calc(var(--r) * 2);
+    width: calc(var(--w) + 6px); // Add a little bit of extra width so that the thumb overflows the track
+    border-radius: var(--r);
+
+    // Render the track (using circles to emulate a capsule shape)
+    // Note: add `1px` difference between the stops so that we have a subtle antialiasing
+    $col: var(--bk-switch-track-color);
+    $a: 1px; // Antialias
+    background:
+      // https://css-tricks.com/drawing-images-with-css-gradients
+      linear-gradient($col, $col) 50% 50% / calc(var(--w) - var(--h)) calc(var(--h)) no-repeat,
+      radial-gradient(circle at var(--r), $col calc(var(--h) / 2 - $a), transparent calc(var(--h) / 2)),
+      radial-gradient(circle at calc(100% - var(--r)), $col calc(var(--h) / 2 - $a), transparent calc(var(--h) / 2));
+    // Render the thumb
+    border-image:
+      radial-gradient(circle at var(--bk-switch-pos),
+        var(--bk-switch-thumb-color) calc(var(--r) - $a),
+        transparent var(--r)
+      ) fill 0 / 1 / 0;
+
+    &:checked {
+      --bk-switch-track-color: #{bk.$theme-switch-slider-default};
+      --bk-switch-thumb-color: #{bk.$theme-switch-knob-default};
+      --bk-switch-pos: var(--pos-end);
+    }
+    &:disabled {
+      --bk-switch-thumb-color: #{bk.$theme-switch-knob-disabled};
+    }
+    &.bk-switch--nonactive {
+      --bk-switch-thumb-color: #{bk.$theme-switch-knob-non-active};
+    }
+
+    @media (prefers-reduced-motion: no-preference) {
+      transition: none 200ms ease-out;
+      transition-property: --bk-switch-pos, --bk-switch-track-color, --bk-switch-thumb-color;
+    }
+  }
+}

src/components/forms/controls/Switch/Switch.stories.tsx

@@ -0,0 +1,50 @@
+
+import type { Meta, StoryObj } from '@storybook/react';
+import * as React from 'react';
+
+import { type SwitchProps, Switch } from './Switch.tsx';
+
+
+type Story = StoryObj<SwitchProps>;
+export default {
+  component: Switch,
+  parameters: {
+    layout: 'centered',
+  },
+  tags: ['autodocs'],
+  argTypes: {},
+  args: {
+    defaultChecked: true,
+  },
+  decorators: [
+    Story => <form onSubmit={event => { event.preventDefault(); }}><Story/></form>,
+  ],
+  render: (args) => <Switch {...args}/>,
+} satisfies Meta<SwitchProps>;
+
+
+export const Checked: Story = {};
+
+export const Unchecked: Story = {
+  args: { defaultChecked: false },
+};
+
+export const NonactiveChecked: Story = {
+  name: 'Nonactive (checked)',
+  args: { nonactive: true, defaultChecked: true },
+};
+
+export const NonactiveUnchecked: Story = {
+  name: 'Nonactive (unchecked)',
+  args: { nonactive: true, defaultChecked: false },
+};
+
+export const DisabledChecked: Story = {
+  name: 'Disabled (checked)',
+  args: { disabled: true, defaultChecked: true },
+};
+
+export const DisabledUnchecked: Story = {
+  name: 'Disabled (unchecked)',
+  args: { disabled: true, defaultChecked: false },
+};

src/components/forms/controls/Switch/Switch.tsx

@@ -0,0 +1,46 @@
+
+import { classNames as cx, type ComponentProps } from '../../../../util/componentUtil.ts';
+import * as React from 'react';
+
+import { Checkbox } from '../Checkbox/Checkbox.tsx';
+import cl from './Switch.module.scss';
+
+
+export { cl as SwitchClassNames };
+
+export type SwitchProps = ComponentProps<'input'> & {
+  /** Whether this component should be unstyled. */
+  unstyled?: undefined | boolean,
+
+  /**
+   * Whether the button is in "nonactive" state. This is a variant of `disabled`, but instead of completely graying
+   * out the button, it only becomes a muted variation of the button's appearance. When true, also implies `disabled`.
+   */
+  nonactive?: undefined | boolean,
+};
+/**
+ * Switch control.
+ */
+export const Switch = (props: SwitchProps) => {
+  const {
+    unstyled = false,
+    nonactive = false,
+    ...propsRest
+  } = props;
+
+  const isInteractive = !propsRest.disabled && !nonactive;
+
+  return (
+    <Checkbox
+      //switch // https://webkit.org/blog/15054/an-html-switch-control
+      disabled={!isInteractive}
+      {...propsRest}
+      unstyled
+      className={cx(
+        { [cl['bk-switch']]: !unstyled },
+        { [cl['bk-switch--nonactive']]: nonactive },
+        propsRest.className,
+      )}
+    />
+  );
+};