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import React, {useCallback, useEffect} from 'react'
import {NativeScrollEvent} from 'react-native'
import {
cancelAnimation,
interpolate,
makeMutable,
useSharedValue,
withSpring,
} from 'react-native-reanimated'
import EventEmitter from 'eventemitter3'
import {ScrollProvider} from '#/lib/ScrollContext'
import {isNative, isWeb} from '#/platform/detection'
import {useMinimalShellMode} from '#/state/shell'
import {useShellLayout} from '#/state/shell/shell-layout'
const WEB_HIDE_SHELL_THRESHOLD = 200
function clamp(num: number, min: number, max: number) {
'worklet'
return Math.min(Math.max(num, min), max)
}
const V0 = makeMutable(
withSpring(0, {
overshootClamping: true,
}),
)
const V1 = makeMutable(
withSpring(1, {
overshootClamping: true,
}),
)
export function MainScrollProvider({children}: {children: React.ReactNode}) {
const {headerHeight} = useShellLayout()
const {headerMode} = useMinimalShellMode()
const startDragOffset = useSharedValue<number | null>(null)
const startMode = useSharedValue<number | null>(null)
const didJustRestoreScroll = useSharedValue<boolean>(false)
const setMode = React.useCallback(
(v: boolean) => {
'worklet'
cancelAnimation(headerMode)
headerMode.value = v ? V1.value : V0.value
},
[headerMode],
)
useEffect(() => {
if (isWeb) {
return listenToForcedWindowScroll(() => {
startDragOffset.value = null
startMode.value = null
didJustRestoreScroll.value = true
})
}
})
const snapToClosestState = useCallback(
(e: NativeScrollEvent) => {
'worklet'
if (isNative) {
if (startDragOffset.value === null) {
return
}
const didScrollDown = e.contentOffset.y > startDragOffset.value
startDragOffset.value = null
startMode.value = null
if (e.contentOffset.y < headerHeight.value) {
// If we're close to the top, show the shell.
setMode(false)
} else if (didScrollDown) {
// Showing the bar again on scroll down feels annoying, so don't.
setMode(true)
} else {
// Snap to whichever state is the closest.
setMode(Math.round(headerMode.value) === 1)
}
}
},
[startDragOffset, startMode, setMode, headerMode, headerHeight],
)
const onBeginDrag = useCallback(
(e: NativeScrollEvent) => {
'worklet'
if (isNative) {
startDragOffset.value = e.contentOffset.y
startMode.value = headerMode.value
}
},
[headerMode, startDragOffset, startMode],
)
const onEndDrag = useCallback(
(e: NativeScrollEvent) => {
'worklet'
if (isNative) {
if (e.velocity && e.velocity.y !== 0) {
// If we detect a velocity, wait for onMomentumEnd to snap.
return
}
snapToClosestState(e)
}
},
[snapToClosestState],
)
const onMomentumEnd = useCallback(
(e: NativeScrollEvent) => {
'worklet'
if (isNative) {
snapToClosestState(e)
}
},
[snapToClosestState],
)
const onScroll = useCallback(
(e: NativeScrollEvent) => {
'worklet'
if (isNative) {
if (startDragOffset.value === null || startMode.value === null) {
if (
headerMode.value !== 0 &&
e.contentOffset.y < headerHeight.value
) {
// If we're close enough to the top, always show the shell.
// Even if we're not dragging.
setMode(false)
}
return
}
// The "mode" value is always between 0 and 1.
// Figure out how much to move it based on the current dragged distance.
const dy = e.contentOffset.y - startDragOffset.value
const dProgress = interpolate(
dy,
[-headerHeight.value, headerHeight.value],
[-1, 1],
)
const newValue = clamp(startMode.value + dProgress, 0, 1)
if (newValue !== headerMode.value) {
// Manually adjust the value. This won't be (and shouldn't be) animated.
// Cancel any any existing animation
cancelAnimation(headerMode)
headerMode.value = newValue
}
} else {
if (didJustRestoreScroll.value) {
didJustRestoreScroll.value = false
// Don't hide/show navbar based on scroll restoratoin.
return
}
// On the web, we don't try to follow the drag because we don't know when it ends.
// Instead, show/hide immediately based on whether we're scrolling up or down.
const dy = e.contentOffset.y - (startDragOffset.value ?? 0)
startDragOffset.value = e.contentOffset.y
if (dy < 0 || e.contentOffset.y < WEB_HIDE_SHELL_THRESHOLD) {
setMode(false)
} else if (dy > 0) {
setMode(true)
}
}
},
[
headerHeight,
headerMode,
setMode,
startDragOffset,
startMode,
didJustRestoreScroll,
],
)
return (
<ScrollProvider
onBeginDrag={onBeginDrag}
onEndDrag={onEndDrag}
onScroll={onScroll}
onMomentumEnd={onMomentumEnd}>
{children}
</ScrollProvider>
)
}
const emitter = new EventEmitter()
if (isWeb) {
const originalScroll = window.scroll
window.scroll = function () {
emitter.emit('forced-scroll')
return originalScroll.apply(this, arguments as any)
}
const originalScrollTo = window.scrollTo
window.scrollTo = function () {
emitter.emit('forced-scroll')
return originalScrollTo.apply(this, arguments as any)
}
}
function listenToForcedWindowScroll(listener: () => void) {
emitter.addListener('forced-scroll', listener)
return () => {
emitter.removeListener('forced-scroll', listener)
}
}
|
