1 files changed, 52 insertions, 0 deletions
diff --git a/src/lib/hooks/useWebScrollRestoration.ts b/src/lib/hooks/useWebScrollRestoration.ts
new file mode 100644
index 000000000..f68fbf0f2
--- /dev/null
+++ b/src/lib/hooks/useWebScrollRestoration.ts
@@ -0,0 +1,52 @@
+import {useMemo, useState, useEffect} from 'react'
+import {EventArg, useNavigation} from '@react-navigation/core'
+
+if ('scrollRestoration' in history) {
+  // Tell the brower not to mess with the scroll.
+  // We're doing that manually below.
+  history.scrollRestoration = 'manual'
+}
+
+function createInitialScrollState() {
+  return {
+    scrollYs: new Map(),
+    focusedKey: null as string | null,
+  }
+}
+
+export function useWebScrollRestoration() {
+  const [state] = useState(createInitialScrollState)
+  const navigation = useNavigation()
+
+  useEffect(() => {
+    function onDispatch() {
+      if (state.focusedKey) {
+        // Remember where we were for later.
+        state.scrollYs.set(state.focusedKey, window.scrollY)
+        // TODO: Strictly speaking, this is a leak. We never clean up.
+        // This is because I'm not sure when it's appropriate to clean it up.
+        // It doesn't seem like popstate is enough because it can still Forward-Back again.
+        // Maybe we should use sessionStorage. Or check what Next.js is doing?
+      }
+    }
+    // We want to intercept any push/pop/replace *before* the re-render.
+    // There is no official way to do this yet, but this works okay for now.
+    // https://twitter.com/satya164/status/1737301243519725803
+    navigation.addListener('__unsafe_action__' as any, onDispatch)
+    return () => {
+      navigation.removeListener('__unsafe_action__' as any, onDispatch)
+    }
+  }, [state, navigation])
+
+  const screenListeners = useMemo(
+    () => ({
+      focus(e: EventArg<'focus', boolean | undefined, unknown>) {
+        const scrollY = state.scrollYs.get(e.target) ?? 0
+        window.scrollTo(0, scrollY)
+        state.focusedKey = e.target ?? null
+      },
+    }),
+    [state],
+  )
+  return screenListeners
+}