diff --git a/packages/controllers/resize-controller/README.md b/packages/controllers/resize-controller/README.md
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+# Resize Controller
+
+The `resize-controller` is a utility module that allows you to observe and react to changes in the size of a web component. It provides a simple way to handle resize events and perform actions based on the new size of the component.
+
+## Installation
+
+You can install the `resize-controller` package using yarn:
+
+```
+yarn add -D @phase2/outline-controller-resize-controller
+```
+
+## Usage
+
+To use the `resize-controller` in your web component, follow these steps:
+
+1. Import the necessary classes and functions from the `lit` package:
+
+```javascript
+import { ResizeController } from '@phase2/outline-controller-resize-controller';
+```
+
+2. Create an instance of the `ResizeController` and pass the host element and options:
+
+```javascript
+resizeController = new ResizeController(this);
+```
+
+## API Reference
+
+### `ResizeController`
+
+The `ResizeController` class provides methods to observe resize events and perform actions based on the new size of the host element.
+
+#### Constructor
+
+```javascript
+new ResizeController(host: ReactiveControllerHost & HTMLElement, options?: ResizeControllerOptions)
+```
+
+- `host`: The host element of the web component.
+- `options` (optional): An object specifying the options for the `ResizeController`. It can include the following properties:
+ - `debounce`: The delay in milliseconds to debounce the resize event. Defaults to `200`.
+ - `breakpoints`: An array of breakpoints for different size ranges. Defaults to `[768]`.
+ - `elementToRerender`: The element to trigger a re-render when the size changes. Defaults to the `host` element.
+
+#### Properties
+
+- `onResize`: A callback function that will be called when the element is resized. Override this method in your component to handle the resize event.
+
+#### Methods
+
+- `hostConnected()`: Called when the host element is connected to the DOM. Observes the element for size changes.
+- `hostDisconnected()`: Called when the host element is disconnected from the DOM. Stops observing size changes.
+
+## Example
+
+Here's an example that demonstrates how to use the `resize-controller` in a web component:
+
+```javascript
+@customElement('my-component')
+export class MyComponent extends LitElement {
+ resizeController = new ResizeController(this, {
+ breakpoints: [768, 1440],
+ });
+
+ render() {
+ const Classes = {
+ 'mobile': this.resizeController.currentBreakpointRange === 0,
+ 'medium': this.resizeController.currentBreakpointRange === 1,
+ 'large': this.resizeController.currentBreakpointRange === 2,
+ };
+ return html`
+
+ Hello World
+
+ `;
+ }
+}
+
+declare global {
+ interface HTMLElementTagNameMap {
+ 'my-component': MyComponent;
+ }
+}
+```
+
+In this example, `resizeController` is initialized to support the following breakpoints:
+
+- 0: 0-767px
+- 1: 768px-1439px
+- 2: 1440px - 100000px
+
+When my-component's width crosses from one range to another, the resize controller will call the component's `render()` function.
diff --git a/packages/controllers/resize-controller/index.ts b/packages/controllers/resize-controller/index.ts
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+++ b/packages/controllers/resize-controller/index.ts
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+export { ResizeController } from './src/resize-controller';
diff --git a/packages/controllers/resize-controller/package.json b/packages/controllers/resize-controller/package.json
new file mode 100644
index 000000000..a2ce96877
--- /dev/null
+++ b/packages/controllers/resize-controller/package.json
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+{
+ "name": "@phase2/outline-controller-resize-controller",
+ "version": "0.0.0",
+ "description": "Controller to help with managing classes / markup updates based on component's width",
+ "keywords": [
+ "outline components",
+ "outline design",
+ "resize"
+ ],
+ "main": "index.ts",
+ "types": "index.ts",
+ "typings": "index.d.ts",
+ "files": [
+ "/dist/",
+ "/src/",
+ "!/dist/tsconfig.build.tsbuildinfo"
+ ],
+ "author": "Phase2 Technology",
+ "repository": {
+ "type": "git",
+ "url": "https://github.com/phase2/outline.git",
+ "directory": "packages/controllers/resize-controller"
+ },
+ "license": "BSD-3-Clause",
+ "scripts": {
+ "build": "node ../../../scripts/build.js",
+ "package": "yarn publish"
+ },
+ "dependencies": {
+ "lit": "^2.3.1"
+ },
+ "devDependencies": {
+ "tslib": "^2.1.0"
+ },
+ "publishConfig": {
+ "access": "public"
+ },
+ "exports": {
+ ".": "./index.ts"
+ }
+}
diff --git a/packages/controllers/resize-controller/src/resize-controller.ts b/packages/controllers/resize-controller/src/resize-controller.ts
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index 000000000..acfe8f160
--- /dev/null
+++ b/packages/controllers/resize-controller/src/resize-controller.ts
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+import { ReactiveControllerHost, ReactiveController } from 'lit';
+
+/**
+ * Debounces a function
+ * @template T
+ * @param {T} func - The function to debounce
+ * @param {number} delay - The delay in milliseconds
+ * @param {boolean} [immediate=false] - Whether to execute the function immediately
+ * @returns {(...args: Parameters) => void} - The debounced function
+ */
+export const debounce = ) => void>(
+ func: T,
+ delay: number,
+ immediate = false
+): ((...args: Parameters) => void) => {
+ let timeoutId: ReturnType | undefined = undefined;
+
+ return function debounced(...args: Parameters) {
+ const executeFunc = () => func(...args);
+
+ clearTimeout(timeoutId);
+
+ if (immediate && timeoutId === undefined) {
+ executeFunc();
+ }
+
+ timeoutId = setTimeout(executeFunc, delay);
+ };
+};
+
+export type breakpointsRangeType = {
+ min: number;
+ max: number;
+};
+
+/**
+ * ResizeController class
+ * @implements {ReactiveController}
+ */
+export class ResizeController implements ReactiveController {
+ host: ReactiveControllerHost & HTMLElement;
+ resizeObserver: ResizeObserver;
+ elementToObserve: Element;
+ options: {
+ debounce: number;
+ breakpoints: number[];
+ elementToRerender: ReactiveControllerHost & HTMLElement;
+ };
+ currentComponentWidth: number;
+ currentBreakpointRange: number;
+ breakpointsRangeArray: breakpointsRangeType[] = [];
+
+ /**
+ * Create a constructor that takes a host and options
+ * @param {ReactiveControllerHost & Element} host - The host element
+ * @param {{debounce?: number; breakpoints?: number[]}} [options={}] - The options object
+ */
+ constructor(
+ host: ReactiveControllerHost & HTMLElement,
+ options: {
+ debounce?: number;
+ breakpoints?: number[];
+ elementToRerender?: ReactiveControllerHost & HTMLElement;
+ } = {}
+ ) {
+ const defaultOptions = {
+ debounce: 200,
+ breakpoints: [768],
+ elementToRerender: host,
+ };
+
+ /**
+ * Remove any undefined variables from options object
+ */
+ const filteredOptionsObject = Object.fromEntries(
+ Object.entries(options).filter(([_, value]) => value !== undefined)
+ );
+ this.options = { ...defaultOptions, ...filteredOptionsObject };
+
+ this.host = host;
+ this.host.addController(this);
+
+ this.initializeBreakpointsRangeType();
+ }
+
+ /**
+ * Initialize the breakpoints range array
+ *
+ * The default breakpoints array ([768]) will create this breakpoints range array:
+ * [{min: 0, max: 767}, {min: 768, max: 100000}]
+ *
+ * If custom breakpoints array is provided, (for example [768, 1200, 2000]) this breakpoints range array will be created:
+ * [{min: 0, max: 767}, {min: 768, max: 1199}, {min: 1200, max: 1999}, {min: 2000, max: 100000}]
+ *
+ */
+ initializeBreakpointsRangeType() {
+ // This will allow create an additional breakpoint from the last custom breakpoint to 100000
+ this.options.breakpoints?.push(100000);
+
+ let minBreakpoint = 0;
+ this.options.breakpoints?.forEach(breakpoint => {
+ const newBreakpointRange = {
+ min: minBreakpoint,
+ max: breakpoint - 1,
+ };
+ minBreakpoint = breakpoint;
+ this.breakpointsRangeArray.push(newBreakpointRange);
+ });
+ }
+
+ /**
+ * Called when the host element is connected to the DOM
+ */
+ hostConnected() {
+ if (!this.host.style.display) {
+ // adding `display: block` to :host of component
+ this.host.style.setProperty(
+ 'display',
+ 'var(--style-added-by-resize-controller, block)'
+ );
+ }
+
+ // Create a new ResizeObserver and pass in the function to be called when the element is resized
+ this.resizeObserver = new ResizeObserver(
+ (entries: ResizeObserverEntry[]) => {
+ // Create a debounced version of the onElementResize function
+ debounce(
+ this.onElementResize.bind(this),
+ this.options.debounce
+ )(entries);
+ }
+ );
+
+ // Get a reference to the element you want to observe
+ this.elementToObserve = this.host;
+
+ // Observe the element for size changes
+ this.resizeObserver.observe(this.elementToObserve);
+ }
+
+ /**
+ * Called when the host element is disconnected from the DOM
+ */
+ hostDisconnected() {
+ this.resizeObserver.disconnect();
+ }
+
+ /**
+ * Called when the element is resized
+ * @param {ResizeObserverEntry[]} _entries - The ResizeObserverEntry array
+ */
+ onElementResize(_entries: ResizeObserverEntry[]) {
+ this.currentComponentWidth = _entries[0].contentRect.width;
+
+ // skip if width is not yet set
+ if (this.currentComponentWidth) {
+ this.calculateNewBreakpointRange();
+ } else if (this.currentComponentWidth === 0) {
+ // eslint-disable-next-line no-console
+ console.warn(
+ `resize-controller: No width detected in <${this.host.localName}>. Please confirm it has display: block`
+ );
+ }
+ }
+
+ /**
+ * Calculate the new breakpoint based on the current width
+ */
+ calculateNewBreakpointRange() {
+ let newBreakpointRange = this.currentBreakpointRange;
+
+ this.breakpointsRangeArray.forEach((breakpoint, index) => {
+ if (
+ this.currentComponentWidth >= breakpoint.min &&
+ this.currentComponentWidth <= breakpoint.max
+ ) {
+ newBreakpointRange = index;
+ }
+ });
+
+ if (newBreakpointRange !== this.currentBreakpointRange) {
+ this.currentBreakpointRange = newBreakpointRange;
+ this.options.elementToRerender.requestUpdate();
+ }
+ }
+}
diff --git a/packages/controllers/resize-controller/tsconfig.build.json b/packages/controllers/resize-controller/tsconfig.build.json
new file mode 100644
index 000000000..5eac9d313
--- /dev/null
+++ b/packages/controllers/resize-controller/tsconfig.build.json
@@ -0,0 +1,9 @@
+{
+ "extends": "../../../tsconfig.json",
+ "compilerOptions": {
+ "rootDir": ".",
+ "outDir": "./dist"
+ },
+ "include": ["index.ts", "src/**/*", "tests/**/*"],
+ "references": [{ "path": "../../outline-core/tsconfig.build.json" }]
+}