commit b8d701ba150aed53a6d0af51886c76193a995051 · kitten.sh/use-interactions

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src/utils/__tests__/observeScrollArea.test.tsx

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       import React, { useState, useRef, useLayoutEffect } from 'react';

     

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       import { mount } from '@cypress/react';

     

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       import { observeScrollArea } from '../observeScrollArea';

     

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       it('reports changes to the scroll area sizes', () => {

     

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         const Resizeable = () => {

     

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           const [minHeight, setMinHeight] = useState(50);

     

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           const toggleHeight = () => setMinHeight(prev => prev === 50 ? 200 : 50);

     

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           return (

     

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             <div style={{ border: '1px solid palevioletred', minHeight }}>

     

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               <button id="increase" onClick={toggleHeight}>Increase Height</button>

     

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             </div>

     

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           );

     

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         };

     

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         const Main = () => {

     

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           const [elements, setElements] = useState<number[]>([]);

     

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           const [height, setHeight] = useState(-1);

     

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           const ref = useRef<HTMLDivElement>(null);

     

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           useLayoutEffect(() => {

     

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             return observeScrollArea(ref.current!, (_width, height) => {

     

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               setHeight(height);

     

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             });

     

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           });

     

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           const addElement = () => setElements(prev => [...prev, prev.length]);

     

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           return (

     

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             <div

     

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               style={{ border: '1px solid red', overflowY: 'scroll', maxHeight: 100 }}

     

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               ref={ref}

     

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             >

     

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               <Resizeable />

     

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               <div style={{ display: 'flex', flexDirection: 'column', minHeight: 40 }}>

     

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                 <span id="size">{height}</span>

     

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                 <button id="add" onClick={addElement}>Add Element</button>

     

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               </div>

     

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               {elements.map(num => (

     

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                 <div style={{ height: 10, width: 10 }} key={num} />

     

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               ))}

     

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             </div>

     

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           );

     

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         };

     

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         mount(<Main />);

     

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         cy.get('#size').contains('92');

     

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         cy.get('#increase').first().click();

     

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         cy.get('#size').contains('242');

     

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         cy.get('#increase').first().click();

     

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         cy.get('#size').contains('92');

     

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         cy.get('#increase').first().click();

     

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         cy.get('#add').first().click();

     

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         cy.get('#size').contains('252');

     

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         cy.get('#add').first().click();

     

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         cy.get('#size').contains('262');

     

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       });

+9 -8

src/utils/observeScrollArea.ts

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       const resizeOptions: ResizeObserverOptions = { box: 'border-box' };

     

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       const mutationObservers: Map<HTMLElement, MutationObserver> = new Map();

     

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       const resizeListeners: Map<HTMLElement, Array<() => void>> = new Map();

     

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               for (let j = 0; j < entry.addedNodes.length; j++) {

     

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                 const node = entry.addedNodes[j];

     

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                 if (node.nodeType === Node.ELEMENT_NODE) {

     

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                   resizeObserver.observe(node as Element);

     

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                   resizeObserver.observe(node as Element, resizeOptions);

     

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                 }

     

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               }

     

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             }

     

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           });

     

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           const childNodes = element.childNodes;

     

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           for (let i = 0; i < childNodes.length; i++)

     

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             if (childNodes[i].nodeType === Node.ELEMENT_NODE)

     

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               resizeObserver.observe(childNodes[i] as Element);

     

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           requestAnimationFrame(() => {

     

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             const childNodes = element.childNodes;

     

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             for (let i = 0; i < childNodes.length; i++)

     

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               if (childNodes[i].nodeType === Node.ELEMENT_NODE)

     

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                 resizeObserver.observe(childNodes[i] as Element, resizeOptions);

     

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             mutationObserver.observe(element, { childList: true });

     

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           });

     

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           mutationObserver.observe(element, { childList: true });

     

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           mutationObservers.set(element, mutationObserver);

     

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         }

     

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         requestAnimationFrame(onResize);

     

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         return () => {

     

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           const listeners = resizeListeners.get(element) || [];