[Nicer Tabs] New native pager (#6868)

* Remove tab bar autoscroll

This will be replaced by a different mechanism.

* Track pager drag gesture in a worklet

* Track pager state change in a worklet

* Track offset relative to current page

* Sync scroll to swipe

* Extract TabBarItem

* Sync scroll to swipe properly

* Implement all interactions

* Clarify more hacks

* Simplify the implementation

I was trying to be too smart and this was causing the current page event to lag behind if you continuously drag. Better to let the library do its job.

* Interpolate the indicator

* Fix an infinite swipe loop

* Add TODO

* Animate header color

* Respect initial page

* Keep layouts in a shared value

* Fix profile and types

* Fast path for initial styles

* Scroll to initial

* Factor out a helper

* Fix positioning

* Scroll into view on tap if needed

* Divide free space proportionally

* Scroll into view more aggressively

* Fix corner case

* Ignore spurious event on iOS

* Simplify the condition

Due to RN onLayout event ordering, we know that by now we'll have container and content sizes already.

* Change boolean state to enum

* Better syncing heuristic

* Rm extra return
This commit is contained in:
dan
2024-12-03 01:29:45 +00:00
committed by GitHub
parent 5a313c2d10
commit cd811114ef
6 changed files with 443 additions and 85 deletions
+2 -3
View File
@@ -1,7 +1,6 @@
import React from 'react'
import {useNavigation} from '@react-navigation/native'
import {usePalette} from '#/lib/hooks/usePalette'
import {NavigationProp} from '#/lib/routes/types'
import {FeedSourceInfo} from '#/state/queries/feed'
import {useSession} from '#/state/session'
@@ -19,7 +18,6 @@ export function HomeHeader(
const {feeds} = props
const {hasSession} = useSession()
const navigation = useNavigation<NavigationProp>()
const pal = usePalette('default')
const hasPinnedCustom = React.useMemo<boolean>(() => {
if (!hasSession) return false
@@ -61,7 +59,8 @@ export function HomeHeader(
onSelect={onSelect}
testID={props.testID}
items={items}
indicatorColor={pal.colors.link}
dragProgress={props.dragProgress}
dragState={props.dragState}
/>
</HomeHeaderLayout>
)
+95 -20
View File
@@ -1,9 +1,18 @@
import React, {forwardRef} from 'react'
import {View} from 'react-native'
import PagerView, {
PagerViewOnPageScrollEventData,
PagerViewOnPageSelectedEvent,
PageScrollStateChangedNativeEvent,
PagerViewOnPageSelectedEventData,
PageScrollStateChangedNativeEventData,
} from 'react-native-pager-view'
import Animated, {
runOnJS,
SharedValue,
useEvent,
useHandler,
useSharedValue,
} from 'react-native-reanimated'
import {atoms as a, native} from '#/alf'
@@ -17,6 +26,8 @@ export interface RenderTabBarFnProps {
selectedPage: number
onSelect?: (index: number) => void
tabBarAnchor?: JSX.Element | null | undefined // Ignored on native.
dragProgress: SharedValue<number> // Ignored on web.
dragState: SharedValue<'idle' | 'dragging' | 'settling'> // Ignored on web.
}
export type RenderTabBarFn = (props: RenderTabBarFnProps) => JSX.Element
@@ -29,19 +40,22 @@ interface Props {
) => void
testID?: string
}
const AnimatedPagerView = Animated.createAnimatedComponent(PagerView)
export const Pager = forwardRef<PagerRef, React.PropsWithChildren<Props>>(
function PagerImpl(
{
children,
initialPage = 0,
renderTabBar,
onPageScrollStateChanged,
onPageSelected,
onPageScrollStateChanged: parentOnPageScrollStateChanged,
onPageSelected: parentOnPageSelected,
testID,
}: React.PropsWithChildren<Props>,
ref,
) {
const [selectedPage, setSelectedPage] = React.useState(0)
const [selectedPage, setSelectedPage] = React.useState(initialPage)
const pagerView = React.useRef<PagerView>(null)
React.useImperativeHandle(ref, () => ({
@@ -50,19 +64,12 @@ export const Pager = forwardRef<PagerRef, React.PropsWithChildren<Props>>(
},
}))
const onPageSelectedInner = React.useCallback(
(e: PageSelectedEvent) => {
setSelectedPage(e.nativeEvent.position)
onPageSelected?.(e.nativeEvent.position)
const onPageSelectedJSThread = React.useCallback(
(nextPosition: number) => {
setSelectedPage(nextPosition)
parentOnPageSelected?.(nextPosition)
},
[setSelectedPage, onPageSelected],
)
const handlePageScrollStateChanged = React.useCallback(
(e: PageScrollStateChangedNativeEvent) => {
onPageScrollStateChanged?.(e.nativeEvent.pageScrollState)
},
[onPageScrollStateChanged],
[setSelectedPage, parentOnPageSelected],
)
const onTabBarSelect = React.useCallback(
@@ -72,21 +79,89 @@ export const Pager = forwardRef<PagerRef, React.PropsWithChildren<Props>>(
[pagerView],
)
const dragState = useSharedValue<'idle' | 'settling' | 'dragging'>('idle')
const dragProgress = useSharedValue(selectedPage)
const didInit = useSharedValue(false)
const handlePageScroll = usePagerHandlers(
{
onPageScroll(e: PagerViewOnPageScrollEventData) {
'worklet'
if (didInit.get() === false) {
// On iOS, there's a spurious scroll event with 0 position
// even if a different page was supplied as the initial page.
// Ignore it and wait for the first confirmed selection instead.
return
}
dragProgress.set(e.offset + e.position)
},
onPageScrollStateChanged(e: PageScrollStateChangedNativeEventData) {
'worklet'
if (dragState.get() === 'idle' && e.pageScrollState === 'settling') {
// This is a programmatic scroll on Android.
// Stay "idle" to match iOS and avoid confusing downstream code.
return
}
dragState.set(e.pageScrollState)
parentOnPageScrollStateChanged?.(e.pageScrollState)
},
onPageSelected(e: PagerViewOnPageSelectedEventData) {
'worklet'
didInit.set(true)
runOnJS(onPageSelectedJSThread)(e.position)
},
},
[parentOnPageScrollStateChanged],
)
return (
<View testID={testID} style={[a.flex_1, native(a.overflow_hidden)]}>
{renderTabBar({
selectedPage,
onSelect: onTabBarSelect,
dragProgress,
dragState,
})}
<PagerView
<AnimatedPagerView
ref={pagerView}
style={[a.flex_1]}
initialPage={initialPage}
onPageScrollStateChanged={handlePageScrollStateChanged}
onPageSelected={onPageSelectedInner}>
onPageScroll={handlePageScroll}>
{children}
</PagerView>
</AnimatedPagerView>
</View>
)
},
)
function usePagerHandlers(
handlers: {
onPageScroll: (e: PagerViewOnPageScrollEventData) => void
onPageScrollStateChanged: (e: PageScrollStateChangedNativeEventData) => void
onPageSelected: (e: PagerViewOnPageSelectedEventData) => void
},
dependencies: unknown[],
) {
const {doDependenciesDiffer} = useHandler(handlers as any, dependencies)
const subscribeForEvents = [
'onPageScroll',
'onPageScrollStateChanged',
'onPageSelected',
]
return useEvent(
event => {
'worklet'
const {onPageScroll, onPageScrollStateChanged, onPageSelected} = handlers
if (event.eventName.endsWith('onPageScroll')) {
onPageScroll(event as any as PagerViewOnPageScrollEventData)
} else if (event.eventName.endsWith('onPageScrollStateChanged')) {
onPageScrollStateChanged(
event as any as PageScrollStateChangedNativeEventData,
)
} else if (event.eventName.endsWith('onPageSelected')) {
onPageSelected(event as any as PagerViewOnPageSelectedEventData)
}
},
subscribeForEvents,
doDependenciesDiffer,
)
}
+8
View File
@@ -97,6 +97,8 @@ export const PagerWithHeader = React.forwardRef<PagerRef, PagerWithHeaderProps>(
scrollY={scrollY}
testID={testID}
allowHeaderOverScroll={allowHeaderOverScroll}
dragProgress={props.dragProgress}
dragState={props.dragState}
/>
</PagerHeaderProvider>
)
@@ -226,6 +228,8 @@ let PagerTabBar = ({
onCurrentPageSelected,
onSelect,
allowHeaderOverScroll,
dragProgress,
dragState,
}: {
currentPage: number
headerOnlyHeight: number
@@ -239,6 +243,8 @@ let PagerTabBar = ({
onCurrentPageSelected?: (index: number) => void
onSelect?: (index: number) => void
allowHeaderOverScroll?: boolean
dragProgress: SharedValue<number>
dragState: SharedValue<'idle' | 'dragging' | 'settling'>
}): React.ReactNode => {
const headerTransform = useAnimatedStyle(() => {
const translateY = Math.min(scrollY.get(), headerOnlyHeight) * -1
@@ -297,6 +303,8 @@ let PagerTabBar = ({
selectedPage={currentPage}
onSelect={onSelect}
onPressSelected={onCurrentPageSelected}
dragProgress={dragProgress}
dragState={dragState}
/>
</View>
</Animated.View>
@@ -151,6 +151,8 @@ let PagerTabBar = ({
selectedPage={currentPage}
onSelect={onSelect}
onPressSelected={onCurrentPageSelected}
dragProgress={undefined as any /* native-only */}
dragState={undefined as any /* native-only */}
/>
</View>
</>
+332 -61
View File
@@ -1,5 +1,16 @@
import React, {useCallback, useEffect, useMemo, useRef, useState} from 'react'
import {useCallback} from 'react'
import {LayoutChangeEvent, ScrollView, StyleSheet, View} from 'react-native'
import Animated, {
interpolate,
runOnJS,
runOnUI,
scrollTo,
SharedValue,
useAnimatedReaction,
useAnimatedRef,
useAnimatedStyle,
useSharedValue,
} from 'react-native-reanimated'
import {usePalette} from '#/lib/hooks/usePalette'
import {PressableWithHover} from '../util/PressableWithHover'
@@ -9,61 +20,245 @@ export interface TabBarProps {
testID?: string
selectedPage: number
items: string[]
indicatorColor?: string
onSelect?: (index: number) => void
onPressSelected?: (index: number) => void
dragProgress: SharedValue<number>
dragState: SharedValue<'idle' | 'dragging' | 'settling'>
}
// How much of the previous/next item we're showing
// to give the user a hint there's more to scroll.
const ITEM_PADDING = 10
const CONTENT_PADDING = 6
// How much of the previous/next item we're requiring
// when deciding whether to scroll into view on tap.
const OFFSCREEN_ITEM_WIDTH = 20
export function TabBar({
testID,
selectedPage,
items,
indicatorColor,
onSelect,
onPressSelected,
dragProgress,
dragState,
}: TabBarProps) {
const pal = usePalette('default')
const scrollElRef = useRef<ScrollView>(null)
const [itemXs, setItemXs] = useState<number[]>([])
const indicatorStyle = useMemo(
() => ({borderBottomColor: indicatorColor || pal.colors.link}),
[indicatorColor, pal],
const scrollElRef = useAnimatedRef<ScrollView>()
const syncScrollState = useSharedValue<'synced' | 'unsynced' | 'needs-sync'>(
'synced',
)
const didInitialScroll = useSharedValue(false)
const contentSize = useSharedValue(0)
const containerSize = useSharedValue(0)
const scrollX = useSharedValue(0)
const layouts = useSharedValue<{x: number; width: number}[]>([])
const itemsLength = items.length
const scrollToOffsetJS = useCallback(
(x: number) => {
scrollElRef.current?.scrollTo({
x,
y: 0,
animated: true,
})
},
[scrollElRef],
)
useEffect(() => {
// On native, the primary interaction is swiping.
// We adjust the scroll little by little on every tab change.
// Scroll into view but keep the end of the previous item visible.
let x = itemXs[selectedPage] || 0
x = Math.max(0, x - OFFSCREEN_ITEM_WIDTH)
scrollElRef.current?.scrollTo({x})
}, [scrollElRef, itemXs, selectedPage])
const indexToOffset = useCallback(
(index: number) => {
'worklet'
const layout = layouts.get()[index]
const availableSize = containerSize.get() - 2 * CONTENT_PADDING
if (!layout) {
// Should not happen, but fall back to equal sizes.
const offsetPerPage = contentSize.get() - availableSize
return (index / (itemsLength - 1)) * offsetPerPage
}
const freeSpace = availableSize - layout.width
const accumulatingOffset = interpolate(
index,
// Gradually shift every next item to the left so that the first item
// is positioned like "left: 0" but the last item is like "right: 0".
[0, itemsLength - 1],
[0, freeSpace],
'clamp',
)
return layout.x - accumulatingOffset
},
[itemsLength, contentSize, containerSize, layouts],
)
const progressToOffset = useCallback(
(progress: number) => {
'worklet'
return interpolate(
progress,
[Math.floor(progress), Math.ceil(progress)],
[
indexToOffset(Math.floor(progress)),
indexToOffset(Math.ceil(progress)),
],
'clamp',
)
},
[indexToOffset],
)
// When we know the entire layout for the first time, scroll selection into view.
useAnimatedReaction(
() => layouts.get().length,
(nextLayoutsLength, prevLayoutsLength) => {
if (nextLayoutsLength !== prevLayoutsLength) {
if (
nextLayoutsLength === itemsLength &&
didInitialScroll.get() === false
) {
didInitialScroll.set(true)
const progress = dragProgress.get()
const offset = progressToOffset(progress)
// It's unclear why we need to go back to JS here. It seems iOS-specific.
runOnJS(scrollToOffsetJS)(offset)
}
}
},
)
// When you swipe the pager, the tabbar should scroll automatically
// as you're dragging the page and then even during deceleration.
useAnimatedReaction(
() => dragProgress.get(),
(nextProgress, prevProgress) => {
if (
nextProgress !== prevProgress &&
dragState.value !== 'idle' &&
// This is only OK to do when we're 100% sure we're synced.
// Otherwise, there would be a jump at the beginning of the swipe.
syncScrollState.get() === 'synced'
) {
const offset = progressToOffset(nextProgress)
scrollTo(scrollElRef, offset, 0, false)
}
},
)
// If the syncing is currently off but you've just finished swiping,
// it's an opportunity to resync. It won't feel disruptive because
// you're not directly interacting with the tabbar at the moment.
useAnimatedReaction(
() => dragState.value,
(nextDragState, prevDragState) => {
if (
nextDragState !== prevDragState &&
nextDragState === 'idle' &&
(syncScrollState.get() === 'unsynced' ||
syncScrollState.get() === 'needs-sync')
) {
const progress = dragProgress.get()
const offset = progressToOffset(progress)
scrollTo(scrollElRef, offset, 0, true)
syncScrollState.set('synced')
}
},
)
// When you press on the item, we'll scroll into view -- unless you previously
// have scrolled the tabbar manually, in which case it'll re-sync on next press.
const onPressUIThread = useCallback(
(index: number) => {
'worklet'
const itemLayout = layouts.get()[index]
if (!itemLayout) {
// Should not happen.
return
}
const leftEdge = itemLayout.x - OFFSCREEN_ITEM_WIDTH
const rightEdge = itemLayout.x + itemLayout.width + OFFSCREEN_ITEM_WIDTH
const scrollLeft = scrollX.get()
const scrollRight = scrollLeft + containerSize.get()
const scrollIntoView = leftEdge < scrollLeft || rightEdge > scrollRight
if (
syncScrollState.get() === 'synced' ||
syncScrollState.get() === 'needs-sync' ||
scrollIntoView
) {
const offset = progressToOffset(index)
scrollTo(scrollElRef, offset, 0, true)
syncScrollState.set('synced')
} else {
// The item is already in view so it's disruptive to
// scroll right now. Do it on the next opportunity.
syncScrollState.set('needs-sync')
}
},
[
syncScrollState,
scrollElRef,
scrollX,
progressToOffset,
containerSize,
layouts,
],
)
const onItemLayout = useCallback(
(i: number, layout: {x: number; width: number}) => {
'worklet'
layouts.modify(ls => {
ls[i] = layout
return ls
})
},
[layouts],
)
const indicatorStyle = useAnimatedStyle(() => {
if (!_WORKLET) {
return {opacity: 0}
}
const layoutsValue = layouts.get()
if (
layoutsValue.length !== itemsLength ||
layoutsValue.some(l => l === undefined)
) {
return {
opacity: 0,
}
}
if (layoutsValue.length === 1) {
return {opacity: 1}
}
return {
opacity: 1,
transform: [
{
translateX: interpolate(
dragProgress.get(),
layoutsValue.map((l, i) => i),
layoutsValue.map(l => l.x + l.width / 2 - contentSize.get() / 2),
),
},
{
scaleX: interpolate(
dragProgress.get(),
layoutsValue.map((l, i) => i),
layoutsValue.map(
l => (l.width - ITEM_PADDING * 2) / contentSize.get(),
),
),
},
],
}
})
const onPressItem = useCallback(
(index: number) => {
runOnUI(onPressUIThread)(index)
onSelect?.(index)
if (index === selectedPage) {
onPressSelected?.(index)
}
},
[onSelect, selectedPage, onPressSelected],
)
// calculates the x position of each item on mount and on layout change
const onItemLayout = React.useCallback(
(e: LayoutChangeEvent, index: number) => {
const x = e.nativeEvent.layout.x
setItemXs(prev => {
const Xs = [...prev]
Xs[index] = x
return Xs
})
},
[],
[onSelect, selectedPage, onPressSelected, onPressUIThread],
)
return (
@@ -76,50 +271,126 @@ export function TabBar({
horizontal={true}
showsHorizontalScrollIndicator={false}
ref={scrollElRef}
contentContainerStyle={styles.contentContainer}>
{items.map((item, i) => {
const selected = i === selectedPage
return (
<PressableWithHover
testID={`${testID}-selector-${i}`}
key={`${item}-${i}`}
onLayout={e => onItemLayout(e, i)}
style={styles.item}
hoverStyle={pal.viewLight}
onPress={() => onPressItem(i)}
accessibilityRole="tab">
<View style={[styles.itemInner, selected && indicatorStyle]}>
<Text
emoji
type="lg-bold"
testID={testID ? `${testID}-${item}` : undefined}
style={[
selected ? pal.text : pal.textLight,
{lineHeight: 20},
]}>
{item}
</Text>
</View>
</PressableWithHover>
)
})}
contentContainerStyle={styles.contentContainer}
onLayout={e => {
containerSize.set(e.nativeEvent.layout.width)
}}
onScrollBeginDrag={() => {
// Remember that you've manually messed with the tabbar scroll.
// This will disable auto-adjustment until after next pager swipe or item tap.
syncScrollState.set('unsynced')
}}
onScroll={e => {
scrollX.value = Math.round(e.nativeEvent.contentOffset.x)
}}>
<Animated.View
onLayout={e => {
contentSize.set(e.nativeEvent.layout.width)
}}
style={{flexDirection: 'row'}}>
{items.map((item, i) => {
return (
<TabBarItem
key={i}
index={i}
testID={testID}
dragProgress={dragProgress}
item={item}
onPressItem={onPressItem}
onItemLayout={onItemLayout}
/>
)
})}
<Animated.View
style={[
indicatorStyle,
{
position: 'absolute',
left: 0,
bottom: 0,
right: 0,
borderBottomWidth: 3,
borderColor: pal.link.color,
},
]}
/>
</Animated.View>
</ScrollView>
<View style={[pal.border, styles.outerBottomBorder]} />
</View>
)
}
function TabBarItem({
index,
testID,
dragProgress,
item,
onPressItem,
onItemLayout,
}: {
index: number
testID: string | undefined
dragProgress: SharedValue<number>
item: string
onPressItem: (index: number) => void
onItemLayout: (index: number, layout: {x: number; width: number}) => void
}) {
const pal = usePalette('default')
const style = useAnimatedStyle(() => {
if (!_WORKLET) {
return {opacity: 0.7}
}
return {
opacity: interpolate(
dragProgress.get(),
[index - 1, index, index + 1],
[0.7, 1, 0.7],
'clamp',
),
}
})
const handleLayout = useCallback(
(e: LayoutChangeEvent) => {
runOnUI(onItemLayout)(index, e.nativeEvent.layout)
},
[index, onItemLayout],
)
return (
<View onLayout={handleLayout}>
<PressableWithHover
testID={`${testID}-selector-${index}`}
style={styles.item}
hoverStyle={pal.viewLight}
onPress={() => onPressItem(index)}
accessibilityRole="tab">
<Animated.View style={[style, styles.itemInner]}>
<Text
emoji
type="lg-bold"
testID={testID ? `${testID}-${item}` : undefined}
style={[pal.text, {lineHeight: 20}]}>
{item}
</Text>
</Animated.View>
</PressableWithHover>
</View>
)
}
const styles = StyleSheet.create({
outer: {
flexDirection: 'row',
},
contentContainer: {
backgroundColor: 'transparent',
paddingHorizontal: 6,
paddingHorizontal: CONTENT_PADDING,
},
item: {
paddingTop: 10,
paddingHorizontal: 10,
paddingHorizontal: ITEM_PADDING,
justifyContent: 'center',
},
itemInner: {
+4 -1
View File
@@ -156,8 +156,10 @@ function HomeScreenReady({
setMinimalShellMode(false)
setDrawerSwipeDisabled(index > 0)
const feed = allFeeds[index]
setSelectedFeed(feed)
// Mutate the ref before setting state to avoid the imperative syncing effect
// above from starting a loop on Android when swiping back and forth.
lastPagerReportedIndexRef.current = index
setSelectedFeed(feed)
logEvent('home:feedDisplayed', {
index,
feedType: feed.split('|')[0],
@@ -173,6 +175,7 @@ function HomeScreenReady({
const onPageScrollStateChanged = React.useCallback(
(state: 'idle' | 'dragging' | 'settling') => {
'worklet'
if (state === 'dragging') {
setMinimalShellMode(false)
}