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import type { OnResizeCallback } from '.'
let observer: ResizeObserver | undefined
const resizeHandlers = new WeakMap<Element, Set<OnResizeCallback>>()
const handleObservation = (entries: ResizeObserverEntry[]) =>
entries.forEach(({ target, contentRect }) => {
return resizeHandlers.get(target)?.forEach(handler => handler(contentRect))
})
export function resizeElement(handler: OnResizeCallback, target: HTMLElement) {
/**
* If there's a resize observer in the ENV then use that too.
*/
if (!observer) {
if (typeof ResizeObserver !== 'undefined') {
observer = new ResizeObserver(handleObservation)
}
}
/**
* Fetch the handlers for the target
*/
let elementHandlers = resizeHandlers.get(target)
/**
* If there are no handlers create a new set for the target
* and then add to the map
*/
if (!elementHandlers) {
elementHandlers = new Set()
resizeHandlers.set(target, elementHandlers)
}
/**
* Add the handler to the target's set
* and observe the target if possible.
*/
elementHandlers.add(handler)
if (observer) {
observer.observe(target)
}
/**
* Cleanup the event handlers and potential observers.
*/
return () => {
const elementHandlers = resizeHandlers.get(target)
if (!elementHandlers) return
elementHandlers.delete(handler)
if (!elementHandlers.size && observer) {
observer.unobserve(target)
}
}
}
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