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import {RefObject, useState} from 'react'; | ||
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import {useEffectOnce, useLatest} from 'react-use'; | ||
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const events: ReadonlySet<keyof WindowEventMap> = new Set<keyof WindowEventMap>([ | ||
'resize', | ||
'scroll', | ||
'touchstart', | ||
'touchmove', | ||
'touchend', | ||
'pageshow', | ||
'load', | ||
'orientationchange', | ||
]); | ||
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export function useSticky<T extends HTMLElement>(elemRef: RefObject<T>) { | ||
import {RefObject, useEffect, useState} from 'react'; | ||
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import throttle from 'lodash/throttle'; | ||
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/** | ||
* Finds the closest parent element with overflow: auto or overflow: scroll. | ||
* | ||
* This function traverses up the DOM tree starting from the given element, | ||
* checking each parent element for overflow: auto or overflow: scroll styles. | ||
* If such an element is found, it is returned as the scroll container. | ||
* If no matching element is found, the global window object is returned. | ||
* | ||
* @param {HTMLElement | null} element - The starting element from which to begin the search. | ||
* @returns {HTMLElement | Window} - The first parent with overflow: auto/scroll, or window. | ||
*/ | ||
const findScrollContainer = (element: HTMLElement | null): HTMLElement | Window => { | ||
let currentElement = element; | ||
while (currentElement) { | ||
const overflow = window.getComputedStyle(currentElement).overflow; | ||
if (overflow === 'auto' || overflow === 'scroll') { | ||
return currentElement; | ||
} | ||
currentElement = currentElement.parentElement; | ||
} | ||
return window; | ||
}; | ||
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/** | ||
* Finds the value of a CSS variable starting from the specified element. | ||
* If not found locally, it will fallback to the global :root. | ||
* | ||
* @param {HTMLElement | null} element - The starting element to search for the CSS variable. | ||
* @param {string} variableName - The name of the CSS variable to search for. | ||
* @returns {number} - The value of the CSS variable or 0 if not found. | ||
*/ | ||
const findCssVariableValue = (element: HTMLElement | null, variableName: string): number => { | ||
let currentElement = element; | ||
while (currentElement) { | ||
const value = getComputedStyle(currentElement).getPropertyValue(variableName); | ||
if (value) { | ||
return parseFloat(value); | ||
} | ||
currentElement = currentElement.parentElement; | ||
} | ||
// Fallback to global :root if not found locally | ||
return ( | ||
parseFloat(getComputedStyle(document.documentElement).getPropertyValue(variableName)) || 0 | ||
); | ||
}; | ||
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interface UseStickyOptions { | ||
/** | ||
* Throttle delay in milliseconds for the scroll event handler. | ||
* This controls how frequently the scroll event is processed. | ||
* Lower values make the scroll handler more responsive but can increase CPU usage. | ||
* | ||
* Default is 100ms. | ||
*/ | ||
throttleDelay?: number; | ||
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/** | ||
* An optional name of a CSS variable that defines an offset value for the sticky element. | ||
* The variable is needed to set an offset if there are other sticky or | ||
* fixed elements on the page. | ||
* | ||
* Default is '--g-md-sticky-offset-compensate'. | ||
*/ | ||
offsetCssVariable?: string; | ||
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/** | ||
* An optional element reference to scope the search for the CSS variable. | ||
* If not provided, the search defaults to the global :root. | ||
*/ | ||
cssVariableScope?: HTMLElement | null; | ||
} | ||
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/** | ||
* useSticky hook | ||
* | ||
* This hook determines whether an element should be in a sticky state based on its position | ||
* relative to the scroll container and a custom offset. | ||
* The offset is calculated based on the CSS variable `--g-md-toolbar-sticky-offset`. | ||
* | ||
* @param {RefObject<T>} elemRef - A reference to the DOM element for which sticky state is being managed. | ||
* @param {UseStickyOptions} options - Options for configuring the hook's behavior. | ||
* @returns {boolean} - A boolean indicating whether the element is currently sticky. | ||
*/ | ||
export function useSticky<T extends HTMLElement>( | ||
elemRef: RefObject<T>, | ||
{ | ||
throttleDelay = 100, | ||
offsetCssVariable = '--g-md-sticky-offset-compensate', | ||
cssVariableScope = null, | ||
}: UseStickyOptions = {}, | ||
) { | ||
const [sticky, setSticky] = useState(false); | ||
const stickyRef = useLatest(sticky); | ||
const [initialOffset, setInitialOffset] = useState<number | null>(null); | ||
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useEffect(() => { | ||
const scrollContainer = findScrollContainer(elemRef.current); | ||
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useEffectOnce(() => { | ||
observe(); | ||
if (elemRef.current) { | ||
if (initialOffset === null) { | ||
// Determine the scope element for the CSS variable search | ||
const scopeElement = cssVariableScope || document.documentElement; | ||
const stickyOffsetCompensate = findCssVariableValue( | ||
scopeElement, | ||
offsetCssVariable, | ||
); | ||
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for (const eventName of events) { | ||
window.addEventListener(eventName, observe, true); | ||
setInitialOffset( | ||
elemRef.current.getBoundingClientRect().top - stickyOffsetCompensate, | ||
); | ||
} | ||
} | ||
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return () => { | ||
for (const eventName of events) { | ||
window.removeEventListener(eventName, observe, true); | ||
// Throttled scroll handler | ||
const handleScroll = throttle(() => { | ||
if (initialOffset !== null) { | ||
const scrollY = | ||
scrollContainer === window | ||
? window.scrollY | ||
: (scrollContainer as HTMLElement).scrollTop; | ||
const newSticky = (initialOffset ?? 0) <= scrollY; | ||
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setSticky(newSticky); | ||
} | ||
}; | ||
}, throttleDelay); | ||
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function observe() { | ||
if (!elemRef.current) return; | ||
const refPageOffset = elemRef.current.getBoundingClientRect().top; | ||
const stickyOffset = parseInt(getComputedStyle(elemRef.current).top, 10); | ||
const stickyActive = refPageOffset <= stickyOffset; | ||
scrollContainer.addEventListener('scroll', handleScroll); | ||
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if (stickyActive && !stickyRef.current) setSticky(true); | ||
else if (!stickyActive && stickyRef.current) setSticky(false); | ||
} | ||
}); | ||
return () => { | ||
scrollContainer.removeEventListener('scroll', handleScroll); | ||
handleScroll.cancel(); // Cancel the throttled function | ||
}; | ||
}, [elemRef, initialOffset, offsetCssVariable, throttleDelay, cssVariableScope]); | ||
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return sticky; | ||
} |