Sync scroll to swipe properly

src/view/com/pager/Pager.tsx

@@ -76,18 +76,19 @@ export const Pager = forwardRef<PagerRef, React.PropsWithChildren<Props>>(
       [pagerView],
     )
 
+    const pendingPage = useSharedValue(selectedPage)
     const dragPage = useSharedValue(selectedPage)
     const dragProgress = useSharedValue(0)
     const dragState = useSharedValue<'idle' | 'settling' | 'dragging'>('idle')
     const handlePageScroll = usePagerHandlers(
+      // These events don't fire exactly the same way on Android and iOS.
+      // In these handlers we normalize the behavior to have consistent output values.
       {
         onPageScroll(e: PagerViewOnPageScrollEventData) {
           'worklet'
           let {position, offset} = e
-          if (position === dragPage.value) {
-            dragProgress.set(offset)
-          } else {
-            const offsetFromPage = position + offset - dragPage.value
+          if (offset !== 0) {
+            const offsetFromPage = offset + (position - dragPage.value)
             dragProgress.set(offsetFromPage)
           }
         },
@@ -95,12 +96,22 @@ export const Pager = forwardRef<PagerRef, React.PropsWithChildren<Props>>(
           'worklet'
           dragState.set(e.pageScrollState)
           parentOnPageScrollStateChanged?.(e.pageScrollState)
+          if (e.pageScrollState === 'idle') {
+            const page = pendingPage.get()
+            dragPage.set(page)
+            dragProgress.set(0)
+            runOnJS(onPageSelectedJSThread)(page)
+          }
         },
         onPageSelected(e: PagerViewOnPageSelectedEventData) {
           'worklet'
-          dragPage.set(e.position)
-          dragProgress.set(0)
-          runOnJS(onPageSelectedJSThread)(e.position)
+          pendingPage.set(e.position)
+          if (dragState.value === 'idle') {
+            const page = e.position
+            dragPage.set(page)
+            dragProgress.set(0)
+            runOnJS(onPageSelectedJSThread)(e.position)
+          }
         },
       },
       [parentOnPageScrollStateChanged],

src/view/com/pager/TabBar.tsx

@@ -4,7 +4,6 @@ import Animated, {
   scrollTo,
   useAnimatedReaction,
   useAnimatedRef,
-  useAnimatedStyle,
   useSharedValue,
 } from 'react-native-reanimated'
 
@@ -47,24 +46,17 @@ export function TabBar({
   const {dragPage, dragProgress} = dragGesture
 
   useAnimatedReaction(
-    () => dragPage.get(),
-    (page, prevPage) => {
-      if (page !== prevPage) {
+    () => dragPage.get() + dragProgress.get(),
+    (next, prev) => {
+      if (next !== prev) {
         const offsetPerPage = contentSize.get() - containerSize.get()
-        const offset = (dragPage.get() / (itemsLength - 1)) * offsetPerPage
+        const offset = (next / (itemsLength - 1)) * offsetPerPage
         scrollTo(scrollElRef, offset, 0, false)
+        return
       }
     },
   )
 
-  const contentStyle = useAnimatedStyle(() => {
-    const offsetPerPage = contentSize.get() - containerSize.get()
-    const offset = (dragProgress.get() / (itemsLength - 1)) * offsetPerPage
-    return {
-      transform: [{translateX: -offset}],
-    }
-  })
-
   return (
     <View
       testID={testID}
@@ -83,12 +75,7 @@ export function TabBar({
           onLayout={e => {
             contentSize.set(e.nativeEvent.layout.width)
           }}
-          style={[
-            contentStyle,
-            {
-              flexDirection: 'row',
-            },
-          ]}>
+          style={{flexDirection: 'row'}}>
           {items.map((item, i) => {
             return (
               <TabBarItem