question: How about add a ResizeObserverProvider?

[kvii]

ResizeObserverDelegate.registerHandler can be called multiple time.

vueuc/src/resize-observer/src/delegate.ts

Lines 27 to 39 in a578387

	registerHandler (el: Element, handler: ResizeHandler): void {
	this.elHandlersMap.set(el, handler)
	this.observer.observe(el)
	}
	unregisterHandler (el: Element): void {
	if (!this.elHandlersMap.has(el)) {
	return
	}
	this.elHandlersMap.delete(el)
	this.observer.unobserve(el)
	}
	}

And these methods can be used for any file that has been imported the delegate.

vueuc/src/resize-observer/src/VResizeObserver.ts

Line 9 in a578387

import delegate from './delegate'

So, is there need a naive-ui-style api like below?

// App.vue
<NResizeObserverProvider>
    <content />
</NResizeObserverProvider>

// YourComponent.vue
<script setup>
const divRef1 = ref(null)
const divRef2 = ref(null)

const observer = useResizeObserver()
observer.add(divRef1, onResize1)
observer.add(divRef2, onResize2)
</script>

<template>
    <div>
        <div ref="divRef1" />
        <div ref="divRef2" />
    </div>
</template>

So we can use multiple observer at once.