Added color reducer. Performed state management refactor to prevent circular behavior.

package.json

@@ -13,7 +13,8 @@
     "lint": "eslint .",
     "preview": "vite preview",
     "test:wasm": "cargo test --lib --manifest-path colorlib/Cargo.toml",
-    "test:wasmdoc": "cargo test --doc --manifest-path colorlib/Cargo.toml"
+    "test:wasmdoc": "cargo test --doc --manifest-path colorlib/Cargo.toml",
+    "test": "vitest"
   },
   "dependencies": {
     "motion": "^12.23.12",
@@ -35,12 +36,14 @@
     "eslint-plugin-react-hooks": "^5.2.0",
     "eslint-plugin-react-refresh": "^0.4.19",
     "globals": "^16.0.0",
+    "jsdom": "^26.1.0",
     "prettier": "^3.5.3",
     "typescript": "~5.8.3",
     "typescript-eslint": "^8.30.1",
     "vite": "^6.3.5",
     "vite-plugin-top-level-await": "^1.5.0",
-    "vite-plugin-wasm": "^3.4.1"
+    "vite-plugin-wasm": "^3.4.1",
+    "vitest": "^3.2.4"
   },
   "prettier": {
     "importOrder": [

src/components/ColorValues/ColorValues.tsx

@@ -1,13 +1,10 @@
-import styles from "./ColorValues.module.css";
+import * as colorlib from "colorlib";
 
-function ColorValues() {
+import styles from "./ColorValues.module.css";
-  return (
+import SpaceEditor from "./SpaceEditor";
-    <div className={styles.container}>
+
-      <div className={styles.valueItem}>RGB: 255, 0, 0</div>
+function ColorValues({ selectedColor }: { selectedColor: colorlib.Color }) {
-      <div className={styles.valueItem}>HEX: #FF0000</div>
+  return <div className={styles.wrapper}></div>;
-      <div className={styles.valueItem}>HSL: 0, 100%, 50%</div>
-    </div>
-  );
 }
 
 export default ColorValues;

src/components/ColorValues/SpaceEditor.tsx

@@ -0,0 +1,9 @@
+import * as colorlib from "colorlib";
+
+import styles from "./SpaceEditor.module.css";
+
+function SpaceEditor({}: {}) {
+  return;
+}
+
+export default SpaceEditor;

src/components/ColorValues/ValueEditor.module.css

@@ -2,7 +2,7 @@
   display: flex;
   align-items: stretch;
   width: 100%;
-  height: 100%;
+  height: var(--height, 25px);
   font-family: monospace;
   border: 1px solid black;
   border-top: none;
@@ -27,11 +27,16 @@
   aspect-ratio: 1 / 1;
 }
 
-.sliderWrapper {
+.sliderSection {
   position: relative;
   flex-grow: 1;
 }
 
+.sliderWrapper {
+  width: 100%;
+  height: 100%;
+}
+
 .sliderBar {
   position: absolute;
   top: 0;

src/components/ColorValues/ValueEditor.tsx

@@ -1,91 +1,62 @@
 import { useCallback, useEffect, useRef, useState } from "react";
-import type { ChangeEvent, Dispatch, RefObject, SetStateAction } from "react";
+import type { ChangeEvent, RefObject } from "react";
 
 import clsx from "clsx";
 
-import type { CartesianSpace } from "@/types";
+import type { CartesianSpace, Range, Setter, Timeout } from "@/types";
-import { minmax, setMeasurements } from "@/util";
+import { Direction } from "@/types";
+import { minmax, setMeasurements, valueToPosition } from "@/util";
 import { useScroll } from "@hooks/scroll";
-import { Direction, useSlider } from "@hooks/slider";
+import { useSlider } from "@hooks/slider";
 import { useResize } from "@hooks/window";
 
 import styles from "./ValueEditor.module.css";
 
-// Types
-type Timeout = ReturnType<typeof setTimeout>;
-interface Range {
-  min: number;
-  max: number;
-}
-
-// Calculation functions
-const getPositionFromValue = (
-  newValue: number,
-  maxValue: number,
-  range: Range,
-) => {
-  const newPosition = parseFloat(
-    (
-      ((newValue + Math.abs(range.min)) /
-        (Math.abs(range.min) + Math.abs(range.max))) *
-      maxValue
-    ).toFixed(0),
-  );
-  return newPosition;
-};
-
-const getValueFromPosition = (
-  newPosition: number,
-  maxValue: number,
-  range: Range,
-) => {
-  const newValue = parseFloat(
-    (
-      (newPosition / maxValue) * (Math.abs(range.min) + Math.abs(range.max)) -
-      Math.abs(range.min)
-    ).toFixed(0),
-  );
-  return newValue;
-};
-
 // Component
 function ValueEditor({
   componentSymbol,
-  range,
+  valueRange,
   value,
   setValue,
+  scale = 1,
 }: {
   componentSymbol: string;
-  range: Range;
+  valueRange: Range;
   value: number;
-  setValue: Dispatch<SetStateAction<number>>;
+  setValue: Setter<number>;
+  scale?: number;
 }) {
   // Set up component state
   const direction = Direction.HORIZONTAL;
   const [origin, setOrigin] = useState<CartesianSpace>({ x: 0, y: 0 });
   const [dimensions, setDimensions] = useState<CartesianSpace>({ x: 0, y: 0 });
-  const [position, setPosition] = useState(0);
+  const position = useRef(0);
+
+  useEffect(() => {
+    position.current = valueToPosition(value, dimensions.x, valueRange);
+  }, [value, dimensions, valueRange]);
 
   // Handler functions
   const handleInputChange = (e: ChangeEvent<HTMLInputElement>) => {
     const inputValue = parseInt(e.target.value, 10);
     if (!isNaN(inputValue)) {
-      const newValue = minmax(inputValue, range.min, range.max);
+      const actualValue = inputValue / scale;
-      const newPosition = getPositionFromValue(newValue, dimensions.x, range);
+      const newValue = minmax(actualValue, valueRange.min, valueRange.max);
 
       setValue(newValue);
-      setPosition(newPosition);
     } else {
-      setValue(range.min);
+      setValue(valueRange.min);
-      setPosition(0);
     }
   };
 
   const handleValueStep = (step: number) => {
     setValue((prev) => {
-      const newValue = minmax(prev + step, range.min, range.max);
+      const scaledStep = step / scale;
-      const newPosition = getPositionFromValue(newValue, dimensions.x, range);
+      const newValue = minmax(
-      setPosition(newPosition);
+        prev + scaledStep,
+        valueRange.min,
+        valueRange.max,
+      );
       return newValue;
     });
   };
@@ -95,7 +66,9 @@ function ValueEditor({
     direction,
     origin,
     dimensions,
-    setPosition,
+    valueRange,
+    value,
+    setValue,
   });
 
   // Set component dimensions for slider hook
@@ -106,17 +79,6 @@ function ValueEditor({
     );
   }, [sliderRef, setOrigin, setDimensions]);
 
-  // Update value when position, etc. changes
-  useEffect(() => {
-    const maxValue = dimensions.x;
-    if (maxValue > 0) {
-      const newValue = getValueFromPosition(position, maxValue, range);
-      setValue(newValue);
-    } else {
-      setValue(range.min);
-    }
-  }, [dimensions, position, range, setValue]);
-
   return (
     <div
       className={styles.componentWrapper}
@@ -128,9 +90,8 @@ function ValueEditor({
 
       <Slider
         sliderRef={sliderRef}
-        position={position}
+        position={position.current}
-        value={value}
+        dimensions={dimensions}
-        range={range}
         componentSymbol={componentSymbol}
       />
 
@@ -143,9 +104,10 @@ function ValueEditor({
       <Value
         value={value}
         onChange={handleInputChange}
-        range={range}
+        valueRange={valueRange}
         componentSymbol={componentSymbol}
         handleValueStep={handleValueStep}
+        scale={scale}
       />
 
       <Button
@@ -173,33 +135,33 @@ function Label({ componentSymbol }: { componentSymbol: string }) {
 function Slider({
   sliderRef,
   position,
-  value,
+  dimensions,
-  range,
   componentSymbol,
 }: {
   sliderRef: RefObject<HTMLDivElement | null>;
   position: number;
-  value: number;
+  dimensions: CartesianSpace;
-  range: { min: number; max: number };
   componentSymbol: string;
 }) {
   return (
-    <div
+    <div className={clsx(styles.section, styles.sliderSection)}>
-      className={clsx(styles.section, styles.sliderWrapper)}
-      ref={sliderRef}
-      role="slider"
-      aria-valuemin={range.min}
-      aria-valuemax={range.max}
-      aria-valuenow={value}
-      aria-labelledby={`${componentSymbol}-label`}
-      tabIndex={0}
-      data-cy={`${componentSymbol}-slider`}
-    >
       <div
-        className={styles.sliderBar}
+        className={styles.sliderWrapper}
-        style={{ width: position }}
+        ref={sliderRef}
-        data-cy={`${componentSymbol}-slider-bar`}
+        role="slider"
-      ></div>
+        aria-valuemin={0}
+        aria-valuemax={dimensions.x}
+        aria-valuenow={position}
+        aria-labelledby={`${componentSymbol}-label`}
+        tabIndex={0}
+        data-cy={`${componentSymbol}-slider`}
+      >
+        <div
+          className={styles.sliderBar}
+          style={{ width: position }}
+          data-cy={`${componentSymbol}-slider-bar`}
+        ></div>
+      </div>
     </div>
   );
 }
@@ -240,15 +202,17 @@ function Button({
 function Value({
   value,
   onChange,
-  range,
+  valueRange,
   componentSymbol,
   handleValueStep,
+  scale,
 }: {
   value: number;
   onChange: (e: ChangeEvent<HTMLInputElement>) => void;
-  range: { min: number; max: number };
+  valueRange: { min: number; max: number };
   componentSymbol: string;
   handleValueStep: (step: number) => void;
+  scale: number;
 }) {
   const valueRef = useRef(null);
   const valueScroller = useScroll({
@@ -263,9 +227,7 @@ function Value({
     }
 
     return () => {
-      if (valueRef.current) {
+      valueScroller.removeScrollListener();
-        valueScroller.removeScrollListener();
-      }
     };
   }, [valueScroller]);
 
@@ -274,13 +236,13 @@ function Value({
       <input
         type="text"
         ref={valueRef}
-        value={value}
+        value={Math.round(value * scale)}
         onChange={onChange}
         className={styles.value}
         onFocus={(e) => e.target.select()}
         aria-label={`${componentSymbol} value input`}
-        aria-valuemin={range.min}
+        aria-valuemin={valueRange.min}
-        aria-valuemax={range.max}
+        aria-valuemax={valueRange.max}
         aria-valuenow={value}
         data-cy={`${componentSymbol}-value-input`}
       />
@@ -294,35 +256,30 @@ function useLongPressRepeat(
   startDelay = 650,
   repeatInterval = 150,
 ) {
-  const [pressing, setPressing] = useState(false);
+  const timeoutRef = useRef<Timeout>(null);
-  const timerRef = useRef<Timeout>(null);
   const intervalRef = useRef<Timeout>(null);
 
-  const start = useCallback(
+  const cleanup = () => {
-    (e: Event | any) => {
+    if (timeoutRef.current) clearTimeout(timeoutRef.current);
-      e.preventDefault();
-      setPressing(true);
-      timerRef.current = setTimeout(() => {
-        callback();
-        intervalRef.current = setInterval(callback, repeatInterval);
-      }, startDelay);
-    },
-    [callback, startDelay, repeatInterval],
-  );
-
-  const stop = useCallback(() => {
-    setPressing(false);
-
-    if (timerRef.current) clearTimeout(timerRef.current);
     if (intervalRef.current) clearInterval(intervalRef.current);
-  }, []);
+    timeoutRef.current = null;
+    intervalRef.current = null;
+  };
 
-  useEffect(() => {
+  // Intentional 'any' to avoid overly complex typing
-    return () => {
+  const start = (e: Event | any) => {
-      if (timerRef.current) clearTimeout(timerRef.current);
+    e.preventDefault();
-      if (intervalRef.current) clearInterval(intervalRef.current);
+    cleanup();
-    };
+
-  }, []);
+    timeoutRef.current = setTimeout(() => {
+      callback();
+      intervalRef.current = setInterval(callback, repeatInterval);
+    }, startDelay);
+  };
+
+  const stop = cleanup;
+
+  useEffect(() => cleanup, []);
 
   return {
     onMouseDown: start,
@@ -330,8 +287,8 @@ function useLongPressRepeat(
     onMouseLeave: stop,
     onTouchStart: start,
     onTouchEnd: stop,
+    // Intentional 'any' to avoid overly complex typing
     onContextMenu: (e: Event | any) => e.preventDefault(),
-    pressing: pressing.toString(),
   };
 }
 

src/components/ColorValues/ValueEditorTest.cy.tsx

@@ -1,16 +1,26 @@
-import { useState } from "react";
+import { useReducer } from "react";
+
+import { Color } from "colorlib";
+
+import { colorReducer, createColorActions } from "@hooks/color";
 
 import ValueEditor from "./ValueEditor";
 
+const initialState = {
+  color: Color.from_hex("000"),
+};
+
 function TestWrapper() {
-  const [value, setValue] = useState(0);
+  const [state, dispatch] = useReducer(colorReducer, initialState);
+  const actions = createColorActions(dispatch);
+
   return (
-    <div style={{ width: 400, height: 25 }}>
+    <div style={{ width: 400 }}>
       <ValueEditor
         componentSymbol="R"
-        range={{ min: 0, max: 255 }}
+        valueRange={{ min: 0, max: 255 }}
-        value={value}
+        value={state.color.rgb.r}
-        setValue={setValue}
+        setValue={actions.rgb.setR}
       />
     </div>
   );
@@ -37,9 +47,9 @@ describe("component editor tests", () => {
     cy.dataCy("R-slider")
       .click()
       .dataCy("R-slider-bar")
-      .should("have.css", "width", "141px")
+      .should("have.css", "width", "140px")
       .dataCy("R-value-input")
-      .should("have.value", "128");
+      .should("have.value", "127");
 
     // Test slider scroll
     cy.dataCy("R-slider")
@@ -47,7 +57,8 @@ describe("component editor tests", () => {
       .trigger("wheel", { deltaY: -100, eventConstructor: "WheelEvent" })
       .trigger("wheel", { deltaY: -100, eventConstructor: "WheelEvent" })
       .dataCy("R-value-input")
-      .should("have.value", "129");
+      .should("have.value", "128")
+      .wait(50);
 
     // Input focus should select text
     cy.dataCy("R-value-input")
@@ -61,14 +72,15 @@ describe("component editor tests", () => {
       .type("100")
       .should("have.value", "100")
       .dataCy("R-slider-bar")
-      .should("have.css", "width", "111px");
+      .should("have.css", "width", "110px");
 
     // Scrolling input should update value
     cy.dataCy("R-value-input")
       .trigger("wheel", { deltaY: -100, eventConstructor: "WheelEvent" })
-      .should("have.value", "101")
+      .should("have.value", "100")
       .dataCy("R-slider-bar")
-      .should("have.css", "width", "112px");
+      .should("have.css", "width", "111px")
+      .wait(50);
 
     // Test increment/decrement buttons
     cy.dataCy("R-decrement-button")
@@ -114,9 +126,9 @@ describe("component editor tests", () => {
     cy.dataCy("R-slider")
       .click()
       .dataCy("R-slider-bar")
-      .should("have.css", "width", "141px")
+      .should("have.css", "width", "140px")
       .dataCy("R-value-input")
-      .should("have.value", "128");
+      .should("have.value", "127");
 
     // Test button long press repeat
     cy.dataCy("R-decrement-button")
@@ -128,7 +140,7 @@ describe("component editor tests", () => {
       .dataCy("R-decrement-button")
       .trigger("touchend")
       .dataCy("R-value-input")
-      .should("have.value", "125")
+      .should("have.value", "124")
       .dataCy("R-increment-button")
       .trigger("touchstart")
       .then(() => {
@@ -138,6 +150,6 @@ describe("component editor tests", () => {
       .dataCy("R-increment-button")
       .trigger("touchend")
       .dataCy("R-value-input")
-      .should("have.value", "128");
+      .should("have.value", "127");
   });
 });

src/hooks/color.ts

@@ -0,0 +1,143 @@
+import type { Dispatch } from "react";
+
+import * as colorlib from "colorlib";
+
+import type { SetterValueOrCallback } from "@/types";
+
+export interface ColorState {
+  color: colorlib.Color;
+}
+
+export type ColorAction =
+  | { type: "SET_COLOR"; payload: colorlib.Color }
+  | { type: "SET_RGB"; payload: colorlib.RGB }
+  | { type: "SET_HSV"; payload: colorlib.HSV }
+  | { type: "SET_HCL"; payload: colorlib.HCL }
+  | { type: "SET_HEX"; payload: colorlib.Hex }
+  | {
+      type: "SET_VALUE";
+      component: colorlib.Component;
+      payload: SetterValueOrCallback<number>;
+    };
+
+export function colorReducer(
+  state: ColorState,
+  action: ColorAction,
+): ColorState {
+  let comp;
+
+  switch (action.type) {
+    case "SET_COLOR":
+      return { ...state, color: action.payload };
+
+    case "SET_RGB":
+      let rgb = action.payload;
+      return { ...state, color: colorlib.Color.from_rgb(rgb.r, rgb.g, rgb.b) };
+
+    case "SET_HSV":
+      let hsv = action.payload;
+      return { ...state, color: colorlib.Color.from_hsv(hsv.h, hsv.s, hsv.v) };
+
+    case "SET_HCL":
+      let hcl = action.payload;
+      return { ...state, color: colorlib.Color.from_hcl(hcl.h, hcl.c, hcl.l) };
+
+    case "SET_HEX":
+      let hex = action.payload;
+      return { ...state, color: colorlib.Color.from_hex(hex.to_code()) };
+
+    case "SET_VALUE":
+      comp = action.component;
+      let valOrFn = action.payload;
+
+      if (typeof valOrFn === "function") {
+        let prev = state.color.get(comp);
+        return { ...state, color: state.color.update(comp, valOrFn(prev)) };
+      } else {
+        return { ...state, color: state.color.update(comp, valOrFn) };
+      }
+
+    default:
+      return state;
+  }
+}
+
+type Setter = (valOrCallback: SetterValueOrCallback<number>) => void;
+
+export interface CommonColorActions {
+  setColor: (color: colorlib.Color) => void;
+}
+
+export interface RGBColorActions {
+  setRGB: (rgb: colorlib.RGB) => void;
+  setR: Setter;
+  setG: Setter;
+  setB: Setter;
+}
+
+export interface HSVColorActions {
+  setHSV: (hsv: colorlib.HSV) => void;
+  setH: Setter;
+  setS: Setter;
+  setV: Setter;
+}
+
+export interface HCLColorActions {
+  setHCL: (hcl: colorlib.HCL) => void;
+  setH: Setter;
+  setC: Setter;
+  setL: Setter;
+}
+
+export interface HexColorActions {
+  setHex: (hex: colorlib.Hex) => void;
+}
+
+export interface ColorActions {
+  common: CommonColorActions;
+  rgb: RGBColorActions;
+  hsv: HSVColorActions;
+  hcl: HCLColorActions;
+  hex: HexColorActions;
+}
+
+export function createColorActions(
+  dispatch: Dispatch<ColorAction>,
+): ColorActions {
+  const Comp = colorlib.Component;
+  const setValue = (
+    comp: colorlib.Component,
+    payload: SetterValueOrCallback<number>,
+  ) => dispatch({ type: "SET_VALUE", component: comp, payload });
+
+  return {
+    common: {
+      setColor: (payload) => dispatch({ type: "SET_COLOR", payload }),
+    },
+
+    rgb: {
+      setRGB: (rgb) => dispatch({ type: "SET_RGB", payload: rgb }),
+      setR: (val) => setValue(Comp.RGB_R, val),
+      setG: (val) => setValue(Comp.RGB_G, val),
+      setB: (val) => setValue(Comp.RGB_B, val),
+    },
+
+    hsv: {
+      setHSV: (hsv) => dispatch({ type: "SET_HSV", payload: hsv }),
+      setH: (val) => setValue(Comp.HSV_H, val),
+      setS: (val) => setValue(Comp.HSV_S, val),
+      setV: (val) => setValue(Comp.HSV_V, val),
+    },
+
+    hcl: {
+      setHCL: (hcl) => dispatch({ type: "SET_HCL", payload: hcl }),
+      setH: (val) => setValue(Comp.HCL_H, val),
+      setC: (val) => setValue(Comp.HCL_C, val),
+      setL: (val) => setValue(Comp.HCL_L, val),
+    },
+
+    hex: {
+      setHex: (hex) => dispatch({ type: "SET_HEX", payload: hex }),
+    },
+  };
+}

src/hooks/crosshair.tsx

@@ -1,12 +1,13 @@
 import { useCallback, useEffect, useRef, useState } from "react";
-import type { Dispatch, SetStateAction } from "react";
 
-import type { CartesianSpace } from "@/types";
+import type { CartesianSpace, Range, Setter } from "@/types";
 import {
   extractEventCoordinates,
   isLeftMouseButton,
   isTouchEvent,
   minmax,
+  positionToValue,
+  valueToPosition,
 } from "@/util";
 
 if (typeof TouchEvent === "undefined") {
@@ -19,37 +20,57 @@ export function useCrosshair({
   dimensions,
   setXPosition,
   setYPosition,
+  xValue,
+  yValue,
+  setXValue,
+  setYValue,
+  xValueRange,
+  yValueRange,
 }: {
   origin: CartesianSpace;
   dimensions: CartesianSpace;
-  setXPosition: Dispatch<SetStateAction<number>>;
+  setXPosition: Setter<number>;
-  setYPosition: Dispatch<SetStateAction<number>>;
+  setYPosition: Setter<number>;
+  xValue: number;
+  yValue: number;
+  setXValue: Setter<number>;
+  setYValue: Setter<number>;
+  xValueRange: Range;
+  yValueRange: Range;
 }) {
   const [isDragging, setIsDragging] = useState(false);
   const crosshairRef = useRef<HTMLDivElement>(null);
 
   const originRef = useRef(origin);
   const dimensionsRef = useRef(dimensions);
+  const setXValueRef = useRef(setXValue);
+  const setYValueRef = useRef(setYValue);
+  const xValueRangeRef = useRef(xValueRange);
+  const yValueRangeRef = useRef(yValueRange);
 
   useEffect(() => {
     originRef.current = origin;
     dimensionsRef.current = dimensions;
-  }, [origin, dimensions]);
+    setXValueRef.current = setXValue;
+    setYValueRef.current = setYValue;
+    xValueRangeRef.current = xValueRange;
+    yValueRangeRef.current = yValueRange;
+  }, [origin, dimensions, setXValue, setYValue, xValueRange, yValueRange]);
 
-  const calculatePositions = useCallback(
+  const calculatePositions = useCallback((event: MouseEvent | TouchEvent) => {
-    (event: MouseEvent | TouchEvent) => {
+    const orig = originRef.current;
-      const orig = originRef.current;
+    const dims = dimensionsRef.current;
-      const dims = dimensionsRef.current;
 
-      const { clientX, clientY } = extractEventCoordinates(event);
+    const { clientX, clientY } = extractEventCoordinates(event);
 
-      const xPos = minmax(clientX - orig.x, 0, dims.x - 1);
+    const xPos = minmax(clientX - orig.x, 0, dims.x - 1);
-      const yPos = minmax(clientY - orig.y, 0, dims.y - 1);
+    const yPos = minmax(clientY - orig.y, 0, dims.y - 1);
-      setXPosition(xPos);
+    const newXValue = positionToValue(xPos, dims.x - 1, xValueRangeRef.current);
-      setYPosition(yPos);
+    const newYValue = positionToValue(yPos, dims.y - 1, yValueRangeRef.current);
-    },
+
-    [setXPosition, setYPosition],
+    setXValueRef.current(newXValue);
-  );
+    setYValueRef.current(newYValue);
+  }, []);
 
   const handleMove = useCallback(
     (event: MouseEvent | TouchEvent) => {
@@ -101,6 +122,15 @@ export function useCrosshair({
     [calculatePositions, handleMove, handleEnd],
   );
 
+  useEffect(() => {
+    const dims = dimensionsRef.current;
+    const newXPos = valueToPosition(xValue, dims.x - 1, xValueRangeRef.current);
+    const newYPos = valueToPosition(yValue, dims.y - 1, yValueRangeRef.current);
+
+    if (newXPos === newXPos) setXPosition(newXPos);
+    if (newYPos === newYPos) setYPosition(newYPos);
+  }, [xValue, yValue, setXPosition, setYPosition]);
+
   useEffect(() => {
     const currentRef = crosshairRef.current;
     if (currentRef) {

src/hooks/scroll.ts

@@ -35,7 +35,7 @@ export function useScroll<T extends HTMLElement>({
   onScrollDown: ScrollHandler;
   deltaYMultiplier?: number;
 }) {
-  const [_, setScrollLength] = useState(0);
+  const scrollLength = useRef(0);
 
   const onScrollUpRef = useRef(onScrollUp);
   const onScrollDownRef = useRef(onScrollDown);
@@ -49,16 +49,14 @@ export function useScroll<T extends HTMLElement>({
 
   const handleWheelEvent = useCallback((event: WheelEvent) => {
     event.preventDefault();
-    console.log("Handling wheel event.");
 
-    setScrollLength((prev) =>
+    const newScrollLength = handleScroll(
-      handleScroll(
+      scrollLength.current,
-        prev,
+      event.deltaY * deltaYMultiplierRef.current,
-        event.deltaY * deltaYMultiplierRef.current,
+      onScrollDownRef.current,
-        onScrollDownRef.current,
+      onScrollUpRef.current,
-        onScrollUpRef.current,
-      ),
     );
+    scrollLength.current = newScrollLength;
   }, []);
 
   const addScrollListener = useCallback(() => {

src/hooks/slider.tsx

@@ -1,12 +1,15 @@
 import { useCallback, useEffect, useRef, useState } from "react";
-import type { Dispatch, SetStateAction } from "react";
 
-import type { CartesianSpace } from "@/types";
+import type { CartesianSpace, Range, Setter } from "@/types";
+import { Direction } from "@/types";
 import {
+  chooseValueByDirection,
   extractEventCoordinates,
   isLeftMouseButton,
   isTouchEvent,
   minmax,
+  positionToValue,
+  valueToPosition,
 } from "@/util";
 
 import { useScroll } from "./scroll";
@@ -16,19 +19,6 @@ if (typeof TouchEvent === "undefined") {
   window.TouchEvent = window.MouseEvent;
 }
 
-export enum Direction {
-  HORIZONTAL = "horizontal",
-  VERTICAL = "vertical",
-}
-
-function chooseValueByDirection(
-  direction: Direction,
-  xValue: number,
-  yValue: number,
-) {
-  return direction === Direction.HORIZONTAL ? xValue : yValue;
-}
-
 function extractEventCoordinateByDirection(
   event: MouseEvent | TouchEvent,
   direction: Direction,
@@ -41,43 +31,74 @@ export function useSlider({
   direction,
   origin,
   dimensions,
-  setPosition,
+  valueRange,
+  value,
+  setValue,
 }: {
   direction: Direction;
   origin: CartesianSpace;
   dimensions: CartesianSpace;
-  setPosition: Dispatch<SetStateAction<number>>;
+  valueRange: Range;
+  value: number;
+  setValue: Setter<number>;
 }) {
   const [isDragging, setIsDragging] = useState(false);
   const sliderRef = useRef<HTMLDivElement>(null);
 
+  // Slider UI refs
   const directionRef = useRef(direction);
   const originRef = useRef(origin);
   const dimensionsRef = useRef(dimensions);
 
+  // Slider value refs
+  const setValueRef = useRef(setValue);
+  const valueRangeRef = useRef(valueRange);
+  const maxPosition = useRef(0);
+
+  // Internal position management
+  const [position, setPosition] = useState(0);
+  const positionRef = useRef(0);
+
   useEffect(() => {
     directionRef.current = direction;
     originRef.current = origin;
     dimensionsRef.current = dimensions;
-  }, [direction, origin, dimensions]);
+    maxPosition.current = chooseValueByDirection(
+      direction,
+      dimensions.x,
+      dimensions.y,
+    );
+    valueRangeRef.current = valueRange;
+  }, [direction, origin, dimensions, valueRangeRef]);
+
+  useEffect(() => {
+    setValueRef.current = setValue;
+  }, [setValue]);
+
+  useEffect(() => {
+    positionRef.current = position;
+  }, [position]);
 
   // Setup drag handlers
-  const calculatePosition = useCallback(
+  const calculatePosition = useCallback((event: MouseEvent | TouchEvent) => {
-    (event: MouseEvent | TouchEvent) => {
+    const dir = directionRef.current;
-      const dir = directionRef.current;
+    const orig = originRef.current;
-      const orig = originRef.current;
+    const dims = dimensionsRef.current;
-      const dims = dimensionsRef.current;
 
-      const clientCoord = extractEventCoordinateByDirection(event, dir);
+    const clientCoord = extractEventCoordinateByDirection(event, dir);
-      const positionValue = minmax(
+    const newPosition = minmax(
-        clientCoord - chooseValueByDirection(dir, orig.x, orig.y),
+      clientCoord - chooseValueByDirection(dir, orig.x, orig.y),
-        0,
+      0,
-        chooseValueByDirection(dir, dims.x, dims.y),
+      chooseValueByDirection(dir, dims.x, dims.y),
-      );
+    );
-      setPosition(positionValue);
+    const newValue = positionToValue(
-    },
+      newPosition,
-    [setPosition],
+      maxPosition.current,
-  );
+      valueRangeRef.current,
+    );
+
+    setValueRef.current(newValue);
+  }, []);
 
   const handleMove = useCallback(
     (event: MouseEvent | TouchEvent) => {
@@ -120,20 +141,37 @@ export function useSlider({
     const dims = dimensionsRef.current;
     const inc = chooseValueByDirection(dir, 1, -1);
 
-    setPosition((prev: number) =>
+    const newPosition = minmax(
-      minmax(prev + inc, 0, chooseValueByDirection(dir, dims.x, dims.y)),
+      positionRef.current + inc,
+      0,
+      chooseValueByDirection(dir, dims.x, dims.y),
     );
-  }, [setPosition]);
+    const newValue = positionToValue(
+      newPosition,
+      maxPosition.current,
+      valueRangeRef.current,
+    );
+    setValueRef.current(newValue);
+  }, []);
 
   const handleScrollDown = useCallback(() => {
     const dir = directionRef.current;
     const dims = dimensionsRef.current;
     const inc = chooseValueByDirection(dir, -1, 1);
 
-    setPosition((prev: number) =>
+    const newPosition = minmax(
-      minmax(prev + inc, 0, chooseValueByDirection(dir, dims.x, dims.y)),
+      positionRef.current + inc,
+      0,
+      chooseValueByDirection(dir, dims.x, dims.y),
     );
-  }, [setPosition]);
+    const newValue = positionToValue(
+      newPosition,
+      maxPosition.current,
+      valueRangeRef.current,
+    );
+
+    setValueRef.current(newValue);
+  }, []);
 
   const { addScrollListener, removeScrollListener } = useScroll({
     targetRef: sliderRef,
@@ -141,6 +179,15 @@ export function useSlider({
     onScrollDown: handleScrollDown,
   });
 
+  useEffect(() => {
+    const newPosition = valueToPosition(
+      value,
+      maxPosition.current,
+      valueRangeRef.current,
+    );
+    setPosition(newPosition);
+  }, [value, setPosition]);
+
   // Set up entry listeners
   useEffect(() => {
     const currentRef = sliderRef.current;

src/hooks/tests/color.test.ts

@@ -0,0 +1,572 @@
+import * as colorlib from "colorlib";
+import { beforeEach, describe, expect, test } from "vitest";
+
+import { colorReducer, createColorActions } from "../color";
+import type { ColorAction, ColorActions, ColorState } from "../color";
+
+const mockUseReducer = <T extends object, U>(
+  reducer: (state: T, action: U) => T,
+  initialArg: T,
+): [T, (value: U) => void] => {
+  let currentState = initialArg;
+
+  const state = new Proxy({} as T, {
+    get: (_, prop) => currentState[prop as keyof T],
+  });
+
+  const dispatch = (value: U) => {
+    const nextState = reducer(currentState, value);
+    currentState = nextState;
+  };
+  return [state, dispatch];
+};
+
+const expectRGB = (value: colorlib.RGB, expected: colorlib.RGB) => {
+  expect(value.r).toBe(expected.r);
+  expect(value.g).toBe(expected.g);
+  expect(value.b).toBe(expected.b);
+};
+
+const expectHSV = (value: colorlib.HSV, expected: colorlib.HSV) => {
+  expect(value.h).toBe(expected.h);
+  expect(value.s).toBe(expected.s);
+  expect(value.v).toBe(expected.v);
+};
+
+const expectHCL = (value: colorlib.HCL, expected: colorlib.HCL) => {
+  expect(value.h).toBe(expected.h);
+  expect(value.c).toBe(expected.c);
+  expect(value.l).toBe(expected.l);
+};
+
+describe("color reducer", () => {
+  const initialState = { color: colorlib.Color.from_hex("000") };
+
+  describe("set by color", () => {
+    test("set color", () => {
+      const nextColor = colorlib.Color.from_hex("F00");
+      const nextState = colorReducer(initialState, {
+        type: "SET_COLOR",
+        payload: nextColor,
+      });
+      expect(nextState.color.hex.to_code()).toBe(nextColor.hex.to_code());
+    });
+  });
+
+  describe("set by color space", () => {
+    test("set rgb", () => {
+      const nextColor = colorlib.RGB.new(1, 2, 3);
+      const nextState = colorReducer(initialState, {
+        type: "SET_RGB",
+        payload: nextColor,
+      });
+
+      expectRGB(nextState.color.rgb, nextColor);
+    });
+
+    test("set hsv", () => {
+      const nextColor = colorlib.HSV.new(1, 2, 3);
+      const nextState = colorReducer(initialState, {
+        type: "SET_HSV",
+        payload: nextColor,
+      });
+
+      expectHSV(nextState.color.hsv, nextColor);
+    });
+
+    test("set hcl", () => {
+      const nextColor = colorlib.HCL.new(1, 2, 3);
+      const nextState = colorReducer(initialState, {
+        type: "SET_HCL",
+        payload: nextColor,
+      });
+
+      expectHCL(nextState.color.hcl, nextColor);
+    });
+
+    test("set hex", () => {
+      const nextColor = colorlib.Hex.new(1, 2, 3);
+      const nextState = colorReducer(initialState, {
+        type: "SET_HEX",
+        payload: nextColor,
+      });
+
+      expect(nextState.color.hex.to_code()).toBe(nextColor.to_code());
+    });
+  });
+
+  describe("set by component", () => {
+    describe("rgb", () => {
+      test("set rgb r", () => {
+        const nextColor = colorlib.RGB.new(100, 0, 0);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_R,
+          payload: nextColor.r,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+      });
+
+      test("set rgb g", () => {
+        const nextColor = colorlib.RGB.new(0, 100, 0);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_G,
+          payload: nextColor.g,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+      });
+
+      test("set rgb b", () => {
+        const nextColor = colorlib.RGB.new(0, 0, 100);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_B,
+          payload: nextColor.b,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+      });
+    });
+
+    describe("hsv", () => {
+      test("set hsv h", () => {
+        const nextColor = colorlib.HSV.new(100, 0, 0);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_H,
+          payload: nextColor.h,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+      });
+
+      test("set hsv s", () => {
+        const nextColor = colorlib.HSV.new(0, 0.5, 0);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_S,
+          payload: nextColor.s,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+      });
+
+      test("set hsv v", () => {
+        const nextColor = colorlib.HSV.new(0, 0, 0.5);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_V,
+          payload: nextColor.v,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+      });
+    });
+
+    describe("hcl", () => {
+      test("set hcl h", () => {
+        const nextColor = colorlib.HCL.new(100, 0, 0);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_H,
+          payload: nextColor.h,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+      });
+
+      test("set hcl c", () => {
+        const nextColor = colorlib.HCL.new(0, 0.5, 0);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_C,
+          payload: nextColor.c,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+      });
+
+      test("set hcl l", () => {
+        const nextColor = colorlib.HCL.new(0, 0, 0.5);
+        const nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_L,
+          payload: nextColor.l,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+      });
+    });
+  });
+
+  describe("adjust by component", () => {
+    describe("rgb", () => {
+      test("adjust rgb r", () => {
+        let nextColor = colorlib.RGB.new(100, 0, 0);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_R,
+          payload: (prev) => prev + 100,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+
+        nextColor = colorlib.RGB.new(50, 0, 0);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_R,
+          payload: (prev) => prev - 50,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+      });
+
+      test("adjust rgb g", () => {
+        let nextColor = colorlib.RGB.new(0, 100, 0);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_G,
+          payload: (prev) => prev + 100,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+
+        nextColor = colorlib.RGB.new(0, 50, 0);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_G,
+          payload: (prev) => prev - 50,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+      });
+
+      test("adjust rgb b", () => {
+        let nextColor = colorlib.RGB.new(0, 0, 100);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_B,
+          payload: (prev) => prev + 100,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+
+        nextColor = colorlib.RGB.new(0, 0, 50);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.RGB_B,
+          payload: (prev) => prev - 50,
+        });
+        expectRGB(nextState.color.rgb, nextColor);
+      });
+    });
+
+    describe("hsv", () => {
+      test("adjust hsv h", () => {
+        let nextColor = colorlib.HSV.new(100, 0, 0);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_H,
+          payload: (prev) => prev + 100,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+
+        nextColor = colorlib.HSV.new(50, 0, 0);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_H,
+          payload: (prev) => prev - 50,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+      });
+
+      test("adjust hsv s", () => {
+        let nextColor = colorlib.HSV.new(0, 1, 0);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_S,
+          payload: (prev) => prev + 1,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+
+        nextColor = colorlib.HSV.new(0, 0.5, 0);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_S,
+          payload: (prev) => prev - 0.5,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+      });
+
+      test("adjust hsv v", () => {
+        let nextColor = colorlib.HSV.new(0, 0, 1);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_V,
+          payload: (prev) => prev + 1,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+
+        nextColor = colorlib.HSV.new(0, 0, 0.5);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HSV_V,
+          payload: (prev) => prev - 0.5,
+        });
+        expectHSV(nextState.color.hsv, nextColor);
+      });
+    });
+
+    describe("hcl", () => {
+      test("adjust hcl h", () => {
+        let nextColor = colorlib.HCL.new(100, 0, 0);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_H,
+          payload: (prev) => prev + 100,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+
+        nextColor = colorlib.HCL.new(50, 0, 0);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_H,
+          payload: (prev) => prev - 50,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+      });
+
+      test("adjust hcl c", () => {
+        let nextColor = colorlib.HCL.new(0, 1, 0);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_C,
+          payload: (prev) => prev + 1,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+
+        nextColor = colorlib.HCL.new(0, 0.5, 0);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_C,
+          payload: (prev) => prev - 0.5,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+      });
+
+      test("adjust hcl l", () => {
+        let nextColor = colorlib.HCL.new(0, 0, 1);
+        let nextState = colorReducer(initialState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_L,
+          payload: (prev) => prev + 1,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+
+        nextColor = colorlib.HCL.new(0, 0, 0.5);
+        nextState = colorReducer(nextState, {
+          type: "SET_VALUE",
+          component: colorlib.Component.HCL_L,
+          payload: (prev) => prev - 0.5,
+        });
+        expectHCL(nextState.color.hcl, nextColor);
+      });
+    });
+  });
+});
+
+describe("color actions", () => {
+  const initialState = { color: colorlib.Color.from_hex("000") };
+
+  let state: ColorState;
+  let dispatch: (value: ColorAction) => void;
+  let actions: ColorActions;
+
+  beforeEach(() => {
+    [state, dispatch] = mockUseReducer(colorReducer, initialState);
+    actions = createColorActions(dispatch);
+  });
+
+  describe("set by color", () => {
+    test("set color", () => {
+      const nextColor = colorlib.Color.from_hex("FF0000");
+      actions.common.setColor(nextColor);
+      expect(state.color.hex.to_code()).toBe(nextColor.hex.to_code());
+    });
+  });
+
+  describe("set by color space", () => {
+    test("set rgb", () => {
+      const nextColor = colorlib.RGB.new(1, 2, 3);
+      actions.rgb.setRGB(nextColor);
+      expectRGB(state.color.rgb, nextColor);
+    });
+
+    test("set hsv", () => {
+      const nextColor = colorlib.HSV.new(1, 2, 3);
+      actions.hsv.setHSV(nextColor);
+      expectHSV(state.color.hsv, nextColor);
+    });
+
+    test("set hcl", () => {
+      const nextColor = colorlib.HCL.new(1, 2, 3);
+      actions.hcl.setHCL(nextColor);
+      expectHCL(state.color.hcl, nextColor);
+    });
+
+    test("set hex", () => {
+      const nextColor = colorlib.Hex.from_code("FF0000");
+      actions.hex.setHex(nextColor);
+      expect(state.color.hex.to_code()).toBe(nextColor.to_code());
+    });
+  });
+
+  describe("set by component", () => {
+    describe("rgb", () => {
+      test("set rgb r", () => {
+        const nextColor = colorlib.RGB.new(100, 0, 0);
+        actions.rgb.setR(nextColor.r);
+        expectRGB(state.color.rgb, nextColor);
+      });
+
+      test("set rgb g", () => {
+        const nextColor = colorlib.RGB.new(0, 100, 0);
+        actions.rgb.setG(nextColor.g);
+        expectRGB(state.color.rgb, nextColor);
+      });
+
+      test("set rgb b", () => {
+        const nextColor = colorlib.RGB.new(0, 0, 100);
+        actions.rgb.setB(nextColor.b);
+        expectRGB(state.color.rgb, nextColor);
+      });
+    });
+
+    describe("hsv", () => {
+      test("set hsv h", () => {
+        const nextColor = colorlib.HSV.new(100, 0, 0);
+        actions.hsv.setH(nextColor.h);
+        expectHSV(state.color.hsv, nextColor);
+      });
+
+      test("set hsv s", () => {
+        const nextColor = colorlib.HSV.new(0, 0.5, 0);
+        actions.hsv.setS(nextColor.s);
+        expectHSV(state.color.hsv, nextColor);
+      });
+
+      test("set hsv v", () => {
+        const nextColor = colorlib.HSV.new(0, 0, 0.5);
+        actions.hsv.setV(nextColor.v);
+        expectHSV(state.color.hsv, nextColor);
+      });
+    });
+
+    describe("hcl", () => {
+      test("set hcl h", () => {
+        const nextColor = colorlib.HCL.new(100, 0, 0);
+        actions.hcl.setH(nextColor.h);
+        expectHCL(state.color.hcl, nextColor);
+      });
+
+      test("set hcl c", () => {
+        const nextColor = colorlib.HCL.new(0, 0.5, 0);
+        actions.hcl.setC(nextColor.c);
+        expectHCL(state.color.hcl, nextColor);
+      });
+
+      test("set hcl l", () => {
+        const nextColor = colorlib.HCL.new(0, 0, 0.5);
+        actions.hcl.setL(nextColor.l);
+        expectHCL(state.color.hcl, nextColor);
+      });
+    });
+  });
+
+  describe("adjust by component", () => {
+    describe("rgb", () => {
+      test("adjust rgb r", () => {
+        let nextColor = colorlib.RGB.new(100, 0, 0);
+        actions.rgb.setR((prev) => prev + 100);
+        expectRGB(state.color.rgb, nextColor);
+
+        nextColor = colorlib.RGB.new(50, 0, 0);
+        actions.rgb.setR((prev) => prev - 50);
+        expectRGB(state.color.rgb, nextColor);
+      });
+
+      test("adjust rgb g", () => {
+        let nextColor = colorlib.RGB.new(0, 100, 0);
+        actions.rgb.setG((prev) => prev + 100);
+        expectRGB(state.color.rgb, nextColor);
+
+        nextColor = colorlib.RGB.new(0, 50, 0);
+        actions.rgb.setG((prev) => prev - 50);
+        expectRGB(state.color.rgb, nextColor);
+      });
+
+      test("adjust rgb b", () => {
+        let nextColor = colorlib.RGB.new(0, 0, 100);
+        actions.rgb.setB((prev) => prev + 100);
+        expectRGB(state.color.rgb, nextColor);
+
+        nextColor = colorlib.RGB.new(0, 0, 50);
+        actions.rgb.setB((prev) => prev - 50);
+        expectRGB(state.color.rgb, nextColor);
+      });
+    });
+
+    describe("hsv", () => {
+      test("adjust hsv h", () => {
+        let nextColor = colorlib.HSV.new(100, 0, 0);
+        actions.hsv.setH((prev) => prev + 100);
+        expectHSV(state.color.hsv, nextColor);
+
+        nextColor = colorlib.HSV.new(50, 0, 0);
+        actions.hsv.setH((prev) => prev - 50);
+        expectHSV(state.color.hsv, nextColor);
+      });
+
+      test("adjust hsv s", () => {
+        let nextColor = colorlib.HSV.new(0, 1, 0);
+        actions.hsv.setS((prev) => prev + 1);
+        expectHSV(state.color.hsv, nextColor);
+
+        nextColor = colorlib.HSV.new(0, 0.5, 0);
+        actions.hsv.setS((prev) => prev - 0.5);
+        expectHSV(state.color.hsv, nextColor);
+      });
+
+      test("adjust hsv v", () => {
+        let nextColor = colorlib.HSV.new(0, 0, 1);
+        actions.hsv.setV((prev) => prev + 1);
+        expectHSV(state.color.hsv, nextColor);
+
+        nextColor = colorlib.HSV.new(0, 0, 0.5);
+        actions.hsv.setV((prev) => prev - 0.5);
+        expectHSV(state.color.hsv, nextColor);
+      });
+    });
+
+    describe("hcl", () => {
+      test("adjust hcl h", () => {
+        let nextColor = colorlib.HCL.new(100, 0, 0);
+        actions.hcl.setH((prev) => prev + 100);
+        expectHCL(state.color.hcl, nextColor);
+
+        nextColor = colorlib.HCL.new(50, 0, 0);
+        actions.hcl.setH((prev) => prev - 50);
+        expectHCL(state.color.hcl, nextColor);
+      });
+
+      test("adjust hcl c", () => {
+        let nextColor = colorlib.HCL.new(0, 1, 0);
+        actions.hcl.setC((prev) => prev + 1);
+        expectHCL(state.color.hcl, nextColor);
+
+        nextColor = colorlib.HCL.new(0, 0.5, 0);
+        actions.hcl.setC((prev) => prev - 0.5);
+        expectHCL(state.color.hcl, nextColor);
+      });
+
+      test("adjust hcl l", () => {
+        let nextColor = colorlib.HCL.new(0, 0, 1);
+        actions.hcl.setL((prev) => prev + 1);
+        expectHCL(state.color.hcl, nextColor);
+
+        nextColor = colorlib.HCL.new(0, 0, 0.5);
+        actions.hcl.setL((prev) => prev - 0.5);
+        expectHCL(state.color.hcl, nextColor);
+      });
+    });
+  });
+});

src/hooks/tests/crosshairTest.cy.tsx

@@ -11,12 +11,22 @@ function TestSquare() {
   const [dimensions, setDimensions] = useState<CartesianSpace>({ x: 0, y: 0 });
   const [xPosition, setXPosition] = useState(0);
   const [yPosition, setYPosition] = useState(0);
+  const [xValue, setXValue] = useState(0);
+  const [yValue, setYValue] = useState(0);
+  const xValueRange = { min: 0, max: 100 };
+  const yValueRange = { min: 0, max: 100 };
 
   const { crosshairRef, isDragging } = useCrosshair({
     origin,
     dimensions,
     setXPosition,
     setYPosition,
+    xValue,
+    yValue,
+    setXValue,
+    setYValue,
+    xValueRange,
+    yValueRange,
   });
 
   const boundaryRef = useRef<HTMLDivElement>(null);
@@ -98,6 +108,10 @@ function TestSquare() {
           {isDragging ? "True" : "False"}
         </span>
       </p>
+      <p>
+        X Value: <span data-cy="x-value-display">{xValue}</span>
+        <br />Y Value: <span data-cy="y-value-display">{yValue}</span>
+      </p>
     </>
   );
 }

src/hooks/tests/sliderTest.cy.tsx

@@ -1,8 +1,10 @@
 import { useEffect, useRef, useState } from "react";
 
 import type { CartesianSpace } from "@/types";
+import { Direction } from "@/types";
+import { chooseValueByDirection, valueToPosition } from "@/util";
 
-import { Direction, useSlider } from "../slider";
+import { useSlider } from "../slider";
 
 // Test Fixtures
 
@@ -13,13 +15,16 @@ function TestSlider({
 }) {
   const [origin, setOrigin] = useState<CartesianSpace>({ x: 0, y: 0 });
   const [dimensions, setDimensions] = useState<CartesianSpace>({ x: 0, y: 0 });
-  const [position, setPosition] = useState(0);
+  const [value, setValue] = useState(0);
-  const [sliderValue, setSliderValue] = useState(0);
+  const position = useRef(0);
+  const valueRange = { min: 0, max: 100 };
   const { sliderRef, isDragging } = useSlider({
     direction,
     origin,
     dimensions,
-    setPosition,
+    valueRange,
+    value,
+    setValue,
   });
 
   const railRef = useRef<HTMLSpanElement>(null);
@@ -41,12 +46,23 @@ function TestSlider({
     const maxValue =
       direction == Direction.HORIZONTAL ? dimensions.x : dimensions.y;
     if (maxValue > 0) {
-      const percentage = parseFloat(((position / maxValue) * 100).toFixed(3));
+      const percentage = parseFloat(
-      setSliderValue(percentage);
+        ((position.current / maxValue) * 100).toFixed(3),
+      );
+      setValue(percentage);
     } else {
-      setSliderValue(0);
+      setValue(0);
     }
-  }, [dimensions, direction, position]);
+  }, [dimensions, direction]);
+
+  useEffect(() => {
+    const maxPosition = chooseValueByDirection(
+      direction,
+      dimensions.x,
+      dimensions.y,
+    );
+    position.current = valueToPosition(value, maxPosition, valueRange);
+  }, [value, direction, dimensions, valueRange]);
 
   const isHorizontal = direction === Direction.HORIZONTAL;
 
@@ -82,8 +98,8 @@ function TestSlider({
           style={{
             position: "absolute",
             ...(isHorizontal
-              ? { left: position, top: 0 }
+              ? { left: position.current, top: 0 }
-              : { left: 0, top: position }),
+              : { left: 0, top: position.current }),
             width: 50,
             height: 50,
             background: "rgba(255,0,0,0.5)",
@@ -92,8 +108,9 @@ function TestSlider({
         />
       </div>
       <p>
-        Position: <span data-cy="position-display">{position}</span>px
+        Value: <span data-cy="value-display">{value}</span>
-        <br /> Value: <span data-cy="value-display">{sliderValue}</span>
+        <br /> Position:{" "}
+        <span data-cy="position-display">{position.current}</span>px
       </p>
     </>
   );

src/types.ts

@@ -1,4 +1,21 @@
+// Interfaces
 export interface CartesianSpace {
   x: number;
   y: number;
 }
+
+export interface Range {
+  min: number;
+  max: number;
+}
+
+// Types
+export type Setter<T> = (valueOrCallback: SetterValueOrCallback<T>) => void;
+export type SetterValueOrCallback<T> = T | ((prev: T) => T);
+export type Timeout = ReturnType<typeof setTimeout>;
+
+// Enums
+export enum Direction {
+  HORIZONTAL = "horizontal",
+  VERTICAL = "vertical",
+}

src/util.ts

@@ -1,6 +1,7 @@
 import type { RefObject } from "react";
 
-import type { CartesianSpace } from "./types";
+import type { CartesianSpace, Range } from "./types";
+import { Direction } from "./types";
 
 export function minmax(number: number, min: number, max: number) {
   return Math.min(max, Math.max(min, number));
@@ -44,3 +45,47 @@ export function setMeasurements(
     setDimensions({ x: rect.width, y: rect.height });
   }
 }
+
+export function valueToPosition(
+  value: number,
+  maxPosition: number,
+  valueRange: Range,
+) {
+  if (maxPosition <= 0 || !isFinite(value)) return 0;
+
+  const rangeSpan = Math.abs(valueRange.min) + Math.abs(valueRange.max);
+  if (rangeSpan === 0) return 0;
+
+  const position = Math.round(
+    maxPosition *
+      ((value + Math.abs(valueRange.min)) /
+        (Math.abs(valueRange.min) + Math.abs(valueRange.max))),
+  );
+  return position;
+}
+
+export function positionToValue(
+  position: number,
+  maxPosition: number,
+  valueRange: Range,
+) {
+  if (maxPosition <= 0 || !isFinite(position)) return valueRange.min;
+
+  const rangeSpan = Math.abs(valueRange.min) + Math.abs(valueRange.max);
+  if (rangeSpan === 0) return valueRange.min;
+
+  const value =
+    (position / maxPosition) *
+      (Math.abs(valueRange.min) + Math.abs(valueRange.max)) -
+    Math.abs(valueRange.min);
+
+  return value;
+}
+
+export function chooseValueByDirection(
+  direction: Direction,
+  xValue: number,
+  yValue: number,
+) {
+  return direction === Direction.HORIZONTAL ? xValue : yValue;
+}

tsconfig.node.json

@@ -20,5 +20,5 @@
     "noFallthroughCasesInSwitch": true,
     "noUncheckedSideEffectImports": true
   },
-  "include": ["vite.config.ts", "cypress.config.ts"]
+  "include": ["vite.config.ts", "cypress.config.ts", "vitest.config.ts"]
 }

vite.config.ts

@@ -19,4 +19,8 @@ export default defineConfig({
   server: {
     port: 5173,
   },
+  test: {
+    environment: "jsdom",
+    globals: true,
+  },
 });

vitest.config.ts

@@ -0,0 +1,10 @@
+import topLevelAwait from "vite-plugin-top-level-await";
+import wasm from "vite-plugin-wasm";
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  plugins: [wasm(), topLevelAwait()],
+  test: {
+    environment: "jsdom",
+  },
+});