Ensure the Transition stops once DOM Nodes are hidden (#1500)

* ensure that the transitions `stops` once the DOM Node is hidden

* update changelog

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Allow to override the `type` on the `Combobox.Input` ([#1476](https://github.com/tailwindlabs/headlessui/pull/1476))
 - Ensure the the `<Popover.Panel focus>` closes correctly ([#1477](https://github.com/tailwindlabs/headlessui/pull/1477))
 - Only render the `FocusSentinel` if required in the `Tabs` component ([#1493](https://github.com/tailwindlabs/headlessui/pull/1493))
+- Ensure the Transition stops once DOM Nodes are hidden ([#1500](https://github.com/tailwindlabs/headlessui/pull/1500))
 
 ### Added
 

packages/@headlessui-react/src/components/transitions/transition.tsx

@@ -218,17 +218,6 @@ let TransitionChild = forwardRefWithAs(function TransitionChild<
 
   let id = useId()
 
-  let transitionInFlight = useRef(false)
-
-  let nesting = useNesting(() => {
-    // When all children have been unmounted we can only hide ourselves if and only if we are not
-    // transitioning ourselves. Otherwise we would unmount before the transitions are finished.
-    if (!transitionInFlight.current) {
-      setState(TreeStates.Hidden)
-      unregister(id)
-    }
-  })
-
   useEffect(() => {
     if (!id) return
     return register(id)
@@ -280,13 +269,28 @@ let TransitionChild = forwardRefWithAs(function TransitionChild<
     return show ? 'enter' : 'leave'
   })() as 'enter' | 'leave' | 'idle'
 
+  let transitioning = useRef(false)
+
+  let nesting = useNesting(() => {
+    if (transitioning.current) return
+
+    // When all children have been unmounted we can only hide ourselves if and only if we are not
+    // transitioning ourselves. Otherwise we would unmount before the transitions are finished.
+    setState(TreeStates.Hidden)
+    unregister(id)
+  })
+
   useTransition({
     container,
     classes,
     events,
     direction: transitionDirection,
-    onStart: useLatestValue(() => {}),
+    onStart: useLatestValue(() => {
+      transitioning.current = true
+    }),
     onStop: useLatestValue((direction) => {
+      transitioning.current = false
+
       if (direction === 'leave' && !hasChildren(nesting)) {
         // When we don't have children anymore we can safely unregister from the parent and hide
         // ourselves.

packages/@headlessui-react/src/hooks/use-transition.ts

@@ -72,6 +72,17 @@ export function useTransition({
     if (latestDirection.current === 'idle') return // We don't need to transition
     if (!mounted.current) return
 
+    dd.add(() => {
+      if (!node) return
+
+      let rect = node.getBoundingClientRect()
+
+      if (rect.x === 0 && rect.y === 0 && rect.width === 0 && rect.height === 0) {
+        // The node is completely hidden
+        onStop.current(latestDirection.current)
+      }
+    })
+
     dd.dispose()
 
     beforeEvent()