From 996871d88ba3298ed53705a6c865cdfe5ede961a Mon Sep 17 00:00:00 2001
From: dan <dan.abramov@gmail.com>
Date: Tue, 3 Dec 2024 01:11:11 +0000
Subject: [PATCH] Prefetch adjacent Home pages (#6904)

---
 src/view/com/feeds/FeedPage.tsx | 6 ++++--
 src/view/com/posts/Feed.tsx     | 4 ++--
 src/view/screens/Home.tsx       | 5 ++++-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/view/com/feeds/FeedPage.tsx b/src/view/com/feeds/FeedPage.tsx
index 1028d7e641f..44e90a55195 100644
--- a/src/view/com/feeds/FeedPage.tsx
+++ b/src/view/com/feeds/FeedPage.tsx
@@ -32,6 +32,7 @@ const POLL_FREQ = 60e3 // 60sec
 export function FeedPage({
   testID,
   isPageFocused,
+  isPageAdjacent,
   feed,
   feedParams,
   renderEmptyState,
@@ -42,6 +43,7 @@ export function FeedPage({
   feed: FeedDescriptor
   feedParams?: FeedParams
   isPageFocused: boolean
+  isPageAdjacent: boolean
   renderEmptyState: () => JSX.Element
   renderEndOfFeed?: () => JSX.Element
   savedFeedConfig?: AppBskyActorDefs.SavedFeed
@@ -111,11 +113,11 @@ export function FeedPage({
         <FeedFeedbackProvider value={feedFeedback}>
           <Feed
             testID={testID ? `${testID}-feed` : undefined}
-            enabled={isPageFocused}
+            enabled={isPageFocused || isPageAdjacent}
             feed={feed}
             feedParams={feedParams}
             pollInterval={POLL_FREQ}
-            disablePoll={hasNew}
+            disablePoll={hasNew || !isPageFocused}
             scrollElRef={scrollElRef}
             onScrolledDownChange={setIsScrolledDown}
             onHasNew={setHasNew}
diff --git a/src/view/com/posts/Feed.tsx b/src/view/com/posts/Feed.tsx
index c623234b876..fb548491983 100644
--- a/src/view/com/posts/Feed.tsx
+++ b/src/view/com/posts/Feed.tsx
@@ -216,7 +216,7 @@ let Feed = ({
     checkForNewRef.current = checkForNew
   }, [checkForNew])
   React.useEffect(() => {
-    if (enabled) {
+    if (enabled && !disablePoll) {
       const timeSinceFirstLoad = Date.now() - lastFetchRef.current
       // DISABLED need to check if this is causing random feed refreshes -prf
       /*if (timeSinceFirstLoad > REFRESH_AFTER) {
@@ -231,7 +231,7 @@ let Feed = ({
         checkForNewRef.current()
       }
     }
-  }, [enabled, feed, queryClient, scrollElRef])
+  }, [enabled, disablePoll, feed, queryClient, scrollElRef])
   React.useEffect(() => {
     let cleanup1: () => void | undefined, cleanup2: () => void | undefined
     const subscription = AppState.addEventListener('change', nextAppState => {
diff --git a/src/view/screens/Home.tsx b/src/view/screens/Home.tsx
index cadfb489034..91c9ae69abb 100644
--- a/src/view/screens/Home.tsx
+++ b/src/view/screens/Home.tsx
@@ -233,7 +233,7 @@ function HomeScreenReady({
       onPageScrollStateChanged={onPageScrollStateChanged}
       renderTabBar={renderTabBar}>
       {pinnedFeedInfos.length ? (
-        pinnedFeedInfos.map(feedInfo => {
+        pinnedFeedInfos.map((feedInfo, index) => {
           const feed = feedInfo.feedDescriptor
           if (feed === 'following') {
             return (
@@ -241,6 +241,7 @@ function HomeScreenReady({
                 key={feed}
                 testID="followingFeedPage"
                 isPageFocused={selectedFeed === feed}
+                isPageAdjacent={Math.abs(selectedIndex - index) === 1}
                 feed={feed}
                 feedParams={homeFeedParams}
                 renderEmptyState={renderFollowingEmptyState}
@@ -254,6 +255,7 @@ function HomeScreenReady({
               key={feed}
               testID="customFeedPage"
               isPageFocused={selectedFeed === feed}
+              isPageAdjacent={Math.abs(selectedIndex - index) === 1}
               feed={feed}
               renderEmptyState={renderCustomFeedEmptyState}
               savedFeedConfig={savedFeedConfig}
@@ -273,6 +275,7 @@ function HomeScreenReady({
       <FeedPage
         testID="customFeedPage"
         isPageFocused
+        isPageAdjacent={false}
         feed={`feedgen|${PROD_DEFAULT_FEED('whats-hot')}`}
         renderEmptyState={renderCustomFeedEmptyState}
       />