[web-components] refactor color recipes for DI

change/@fluentui-web-components-91e2200b-d44a-48fe-9075-c23eced8be5f.json

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+{
+  "type": "minor",
+  "comment": "add color-vNext folder with recipes and update specs",
+  "packageName": "@fluentui/web-components",
+  "email": "chhol@microsoft.com",
+  "dependentChangeType": "patch"
+}

packages/web-components/src/color-vNext/README.md

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+# Fluent Color Recipes
+
+Color recipes are named colors who's value is algorithmically defined from a variety of inputs. `@fluentui/web-components` relies on these recipes heavily to achieve expressive theming options while maintaining color accessability targets.
+
+## Swatch
+
+A Swatch is a representation of a color that has a `relativeLuminance` value and a method to convert the swatch to a color string. It is used by recipes to determine which colors to use for UI.
+
+### SwatchRGB
+
+A concrete implementation of `Swatch`, it is a swatch with red, green, and blue 64bit color channels .
+
+**Example: Creating a SwatchRGB**
+
+```ts
+import { SwatchRGB } from '@fluentui/web-components';
+
+const red = SwatchRGB.create(1, 0, 0);
+```
+
+## Palette
+
+A palette is a collection `Swatch` instances, ordered by relative luminance, and provides mechanisms to safely retrieve swatches by index and by target contrast ratios. It also contains a `source` color, which is the color from which the palette is
+
+### PaletteRGB
+
+An implementation of `Palette` of `SwatchRGB` instances.
+
+```ts
+// Create a palette from the red swatch
+const palette = PaletteRGB.create(red):
+```

packages/web-components/src/color-vNext/palette.ts

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+import { clamp, ColorRGBA64, ComponentStateColorPalette, parseColorHexRGB } from '@microsoft/fast-colors';
+import { Swatch, SwatchRGB } from './swatch';
+import { binarySearch } from './utilities/binary-search';
+import { directionByIsDark } from './utilities/direction-by-is-dark';
+import { contrast, RelativeLuminance } from './utilities/relative-luminance';
+
+/**
+ * A collection of {@link Swatch} instances
+ * @public
+ */
+export interface Palette<T extends Swatch = Swatch> {
+  readonly source: T;
+  readonly swatches: ReadonlyArray<T>;
+
+  /**
+   * Returns a swatch from the palette that most closely matches
+   * the contrast ratio provided to a provided reference.
+   */
+  colorContrast(reference: Swatch, contrast: number, initialIndex?: number, direction?: 1 | -1): T;
+
+  /**
+   * Returns the index of the palette that most closely matches
+   * the relativeLuminance of the provided swatch
+   */
+  closestIndexOf(reference: RelativeLuminance): number;
+
+  /**
+   * Gets a swatch by index. Index is clamped to the limits
+   * of the palette so a Swatch will always be returned.
+   */
+  get(index: number): T;
+}
+
+export type PaletteRGB = Palette<SwatchRGB>;
+
+export const PaletteRGB = Object.freeze({
+  create(source: SwatchRGB): PaletteRGB {
+    return PaletteRGBImpl.from(source);
+  },
+});
+
+/**
+ * A {@link Palette} representing RGB swatch values.
+ * @public
+ */
+class PaletteRGBImpl implements Palette<SwatchRGB> {
+  /**
+   * {@inheritdoc Palette.source}
+   */
+  public readonly source: SwatchRGB;
+  public readonly swatches: ReadonlyArray<SwatchRGB>;
+  private lastIndex: number;
+  private reversedSwatches: ReadonlyArray<SwatchRGB>;
+  /**
+   *
+   * @param source - The source color for the palette
+   * @param swatches - All swatches in the palette
+   */
+  constructor(source: SwatchRGB, swatches: ReadonlyArray<SwatchRGB>) {
+    this.source = source;
+    this.swatches = swatches;
+
+    this.reversedSwatches = Object.freeze([...this.swatches].reverse());
+    this.lastIndex = this.swatches.length - 1;
+  }
+
+  /**
+   * {@inheritdoc Palette.colorContrast}
+   */
+  public colorContrast(
+    reference: Swatch,
+    contrastTarget: number,
+    initialSearchIndex?: number,
+    direction?: 1 | -1,
+  ): SwatchRGB {
+    if (initialSearchIndex === undefined) {
+      initialSearchIndex = this.closestIndexOf(reference);
+    }
+
+    let source: ReadonlyArray<SwatchRGB> = this.swatches;
+    const endSearchIndex = this.lastIndex;
+    let startSearchIndex = initialSearchIndex;
+
+    if (direction === undefined) {
+      direction = directionByIsDark(reference);
+    }
+
+    const condition = (value: SwatchRGB) => contrast(reference, value) >= contrastTarget;
+
+    if (direction === -1) {
+      source = this.reversedSwatches;
+      startSearchIndex = endSearchIndex - startSearchIndex;
+    }
+
+    return binarySearch(source, condition, startSearchIndex, endSearchIndex);
+  }
+
+  /**
+   * {@inheritdoc Palette.get}
+   */
+  public get(index: number): SwatchRGB {
+    return this.swatches[index] || this.swatches[clamp(index, 0, this.lastIndex)];
+  }
+
+  /**
+   * {@inheritdoc Palette.closestIndexOf}
+   */
+  public closestIndexOf(reference: Swatch): number {
+    const index = this.swatches.indexOf(reference as SwatchRGB);
+
+    if (index !== -1) {
+      return index;
+    }
+
+    const closest = this.swatches.reduce((previous, next) =>
+      Math.abs(next.relativeLuminance - reference.relativeLuminance) <
+      Math.abs(previous.relativeLuminance - reference.relativeLuminance)
+        ? next
+        : previous,
+    );
+
+    return this.swatches.indexOf(closest);
+  }
+
+  /**
+   * Create a color palette from a provided swatch
+   * @param source - The source swatch to create a palette from
+   * @returns
+   */
+  static from(source: SwatchRGB): PaletteRGB {
+    return new PaletteRGBImpl(
+      source,
+      Object.freeze(
+        new ComponentStateColorPalette({
+          baseColor: ColorRGBA64.fromObject(source)!,
+        }).palette.map(x => {
+          const _x = parseColorHexRGB(x.toStringHexRGB())!;
+          return SwatchRGB.create(_x.r, _x.g, _x.b);
+        }),
+      ),
+    );
+  }
+}

packages/web-components/src/color-vNext/recipes/accent-fill.ts

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+import { inRange } from 'lodash-es';
+import { PaletteRGB } from '../palette';
+import { Swatch } from '../swatch';
+import { isDark } from '../utilities/is-dark';
+
+/**
+ * @internal
+ */
+export function accentFill(
+  palette: PaletteRGB,
+  neutralPaletteRGB: PaletteRGB,
+  reference: Swatch,
+  textColor: Swatch,
+  contrastTarget: number,
+  hoverDelta: number,
+  activeDelta: number,
+  focusDelta: number,
+  selectedDelta: number,
+  neutralFillRestDelta: number,
+  neutralFillHoverDelta: number,
+  neutralFillActiveDelta: number,
+) {
+  const accent = palette.source;
+  const referenceIndex = neutralPaletteRGB.closestIndexOf(reference);
+  const swapThreshold = Math.max(neutralFillRestDelta, neutralFillHoverDelta, neutralFillActiveDelta);
+  const direction = referenceIndex >= swapThreshold ? -1 : 1;
+  const paletteLength = palette.swatches.length;
+  const maxIndex = paletteLength - 1;
+  const accentIndex = palette.closestIndexOf(accent);
+  let accessibleOffset = 0;
+
+  while (
+    accessibleOffset < direction * hoverDelta &&
+    inRange(accentIndex + accessibleOffset + direction, 0, paletteLength) &&
+    textColor.contrast(palette.get(accentIndex + accessibleOffset + direction)) >= contrastTarget &&
+    inRange(accentIndex + accessibleOffset + direction + direction, 0, maxIndex)
+  ) {
+    accessibleOffset += direction;
+  }
+
+  const hoverIndex = accentIndex + accessibleOffset;
+  const restIndex = hoverIndex + direction * -1 * hoverDelta;
+  const activeIndex = restIndex + direction * activeDelta;
+  const focusIndex = restIndex + direction * focusDelta;
+  const selectedIndex = restIndex + (isDark(reference) ? selectedDelta * -1 : selectedDelta);
+
+  return {
+    rest: palette.get(restIndex),
+    hover: palette.get(hoverIndex),
+    active: palette.get(activeIndex),
+    focus: palette.get(focusIndex),
+    selected: palette.get(selectedIndex),
+  };
+}

packages/web-components/src/color-vNext/recipes/accent-foreground-cut.ts

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+import { Swatch } from '../swatch';
+import { black, white } from '../utilities/color-constants';
+
+/**
+ * @internal
+ */
+export function accentForegroundCut(reference: Swatch, contrastTarget: number) {
+  return reference.contrast(white) >= contrastTarget ? white : black;
+}

packages/web-components/src/color-vNext/recipes/accent-foreground.ts

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+import { PaletteRGB } from '../palette';
+import { Swatch } from '../swatch';
+import { directionByIsDark } from '../utilities/direction-by-is-dark';
+
+/**
+ * @internal
+ */
+export function accentForeground(
+  palette: PaletteRGB,
+  reference: Swatch,
+  contrastTarget: number,
+  restDelta: number,
+  hoverDelta: number,
+  activeDelta: number,
+  focusDelta: number,
+) {
+  const accent = palette.source;
+  const accentIndex = palette.closestIndexOf(accent);
+  const direction = directionByIsDark(reference);
+  const startIndex =
+    accentIndex +
+    (direction === 1 ? Math.min(restDelta, hoverDelta) : Math.max(direction * restDelta, direction * hoverDelta));
+  const accessibleSwatch = palette.colorContrast(reference, contrastTarget, startIndex, direction);
+  const accessibleIndex1 = palette.closestIndexOf(accessibleSwatch);
+  const accessibleIndex2 = accessibleIndex1 + direction * Math.abs(restDelta - hoverDelta);
+  const indexOneIsRestState = direction === 1 ? restDelta < hoverDelta : direction * restDelta > direction * hoverDelta;
+
+  let restIndex: number;
+  let hoverIndex: number;
+
+  if (indexOneIsRestState) {
+    restIndex = accessibleIndex1;
+    hoverIndex = accessibleIndex2;
+  } else {
+    restIndex = accessibleIndex2;
+    hoverIndex = accessibleIndex1;
+  }
+
+  return {
+    rest: palette.get(restIndex),
+    hover: palette.get(hoverIndex),
+    active: palette.get(restIndex + direction * activeDelta),
+    focus: palette.get(restIndex + direction * focusDelta),
+  };
+}

packages/web-components/src/color-vNext/recipes/neutral-divider.ts

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+import { Swatch } from '../swatch';
+import { PaletteRGB } from '../palette';
+import { directionByIsDark } from '../utilities/direction-by-is-dark';
+
+/**
+ * The neutralDivider color recipe
+ * @param palette - The palette to operate on
+ * @param reference - The reference color
+ * @param delta - The offset from the reference
+ *
+ * @internal
+ */
+export function neutralDivider(palette: PaletteRGB, reference: Swatch, delta: number) {
+  return palette.get(palette.closestIndexOf(reference) + directionByIsDark(reference) * delta);
+}

packages/web-components/src/color-vNext/recipes/neutral-fill-card.ts

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+import { PaletteRGB } from '../palette';
+import { Swatch } from '../swatch';
+
+/**
+ * @internal
+ */
+export function neutralFillCard(palette: PaletteRGB, reference: Swatch, delta: number) {
+  const referenceIndex = palette.closestIndexOf(reference);
+
+  return palette.get(referenceIndex - (referenceIndex < delta ? delta * -1 : delta));
+}

packages/web-components/src/color-vNext/recipes/neutral-fill-input.ts

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+import { PaletteRGB } from '../palette';
+import { Swatch } from '../swatch';
+import { directionByIsDark } from '../utilities/direction-by-is-dark';
+
+/**
+ * @internal
+ */
+export function neutralFillInput(
+  palette: PaletteRGB,
+  reference: Swatch,
+  restDelta: number,
+  hoverDelta: number,
+  activeDelta: number,
+  focusDelta: number,
+  selectedDelta: number,
+) {
+  const direction = directionByIsDark(reference);
+  const referenceIndex = palette.closestIndexOf(reference);
+
+  return {
+    rest: palette.get(referenceIndex - direction * restDelta),
+    hover: palette.get(referenceIndex - direction * hoverDelta),
+    active: palette.get(referenceIndex - direction * activeDelta),
+    focus: palette.get(referenceIndex - direction * focusDelta),
+    selected: palette.get(referenceIndex - direction * selectedDelta),
+  };
+}

packages/web-components/src/color-vNext/recipes/neutral-fill-stealth.ts

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+import { PaletteRGB } from '../palette';
+import { Swatch } from '../swatch';
+
+/**
+ * @internal
+ */
+export function neutralFillStealth(
+  palette: PaletteRGB,
+  reference: Swatch,
+  restDelta: number,
+  hoverDelta: number,
+  activeDelta: number,
+  focusDelta: number,
+  selectedDelta: number,
+  fillRestDelta: number,
+  fillHoverDelta: number,
+  fillActiveDelta: number,
+  fillFocusDelta: number,
+) {
+  const swapThreshold = Math.max(
+    restDelta,
+    hoverDelta,
+    activeDelta,
+    focusDelta,
+    fillRestDelta,
+    fillHoverDelta,
+    fillActiveDelta,
+    fillFocusDelta,
+  );
+
+  const referenceIndex = palette.closestIndexOf(reference);
+  const direction: 1 | -1 = referenceIndex >= swapThreshold ? -1 : 1;
+
+  return {
+    rest: palette.get(referenceIndex + direction * restDelta),
+    hover: palette.get(referenceIndex + direction * hoverDelta),
+    active: palette.get(referenceIndex + direction * activeDelta),
+    focus: palette.get(referenceIndex + direction * focusDelta),
+    selected: palette.get(referenceIndex + direction * selectedDelta),
+  };
+}