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import classnames from "classnames"
type VerticalScrollContainerProps = React.DetailedHTMLProps<
React.HTMLAttributes<HTMLDivElement>,
HTMLDivElement
> & {
scrollingShadows?: boolean
scrollLock?: boolean
contentsId?: string
}
type ReactRef<T> =
| ((instance: T | null) => void)
| React.MutableRefObject<T | null>
| null
function useCombinedRefs<T>(...refs: ReactRef<T>[]): React.RefObject<T> {
const targetRef = React.useRef<T>(null)
React.useEffect(() => {
refs.forEach((ref) => {
if (!ref) return
if (typeof ref === "function") {
ref(targetRef.current || null)
} else {
ref.current = targetRef.current || null
}
})
}, [refs])
return targetRef
}
export const VerticalScrollContainer = React.forwardRef(
(props: VerticalScrollContainerProps, ref: ReactRef<HTMLDivElement>) => {
let {
scrollingShadows,
scrollLock,
className,
children,
contentsId,
style,
...rest
} = props
scrollingShadows = scrollingShadows ?? true
scrollLock = scrollLock ?? true
const scrollContainerRef = useCombinedRefs<HTMLDivElement>(ref)
const [scrollTop, scrollBottom] = useScrollBounds(
scrollContainerRef,
contentsId
)
if (scrollLock) {
useScrollLock(scrollContainerRef, { doNotLockIfNoScroll: true })
}
return (
<div
className="VerticalScrollContainerShadows"
style={{
position: "relative",
height: "100%",
}}
>
{scrollingShadows && (
<ScrollingShadow
direction="down"
size={10}
opacity={getShadowOpacity(0.15, 80, scrollTop)}
/>
)}
<div
className={classnames(className, "VerticalScrollContainer")}
style={{
overflowY: "auto",
position: "absolute",
top: 0,
right: 0,
bottom: 0,
left: 0,
...style,
}}
ref={scrollContainerRef}
{...rest}
>
{children}
</div>
{scrollingShadows && (
<ScrollingShadow
direction="up"
size={10}
opacity={getShadowOpacity(0.15, 80, scrollBottom)}
/>
)}
</div>
)
}
)
function getShadowOpacity(
maxOpacity: number,
maxDistance: number,
scrollDistance: number | undefined
): number {
const distance =
scrollDistance !== undefined ? Math.min(scrollDistance, maxDistance) : 0
return (distance / maxDistance) * maxOpacity
}
const ScrollingShadow = (props: {
direction: "up" | "down"
size: number
opacity: number
}): JSX.Element => {
// "Eased" gradient
// https://larsenwork.com/easing-gradients/
const background = `linear-gradient(
to ${props.direction === "up" ? "bottom" : "top"},
hsla(0, 0%, 0%, 0) 0%,
hsla(0, 0%, 0%, 0.104) 25.8%,
hsla(0, 0%, 0%, 0.45) 60.9%,
hsla(0, 0%, 0%, 0.825) 88.7%,
hsl(0, 0%, 0%) 100%
)`
return (
<div
style={{
position: "absolute",
left: 0,
right: 0,
[props.direction === "up" ? "bottom" : "top"]: 0,
height: `${props.size}px`,
background: background,
opacity: props.opacity,
pointerEvents: "none",
zIndex: 10,
}}
/>
)
}
/**
* A throttled function that returns the available scrollTop and scrollBottom
* @param ref
* @param contentsId when this string changes, it's a signal that the contents have re-rendered and
* the height has likely changed.
*/
function useScrollBounds<ElementType extends HTMLElement>(
ref: React.RefObject<ElementType>,
contentsId?: string
): [number | undefined, number | undefined] {
const [scrollTop, onScrollTop] = useState<number | undefined>(undefined)
const [scrollBottom, onScrollBottom] = useState<number | undefined>(
undefined
)
useEffect(() => {
const el = ref.current!
if (el) {
let pendingUpdate = false
function onScroll(): void {
const { scrollTop, scrollHeight, offsetHeight } = el
onScrollTop(scrollTop)
onScrollBottom(scrollHeight - offsetHeight - scrollTop)
pendingUpdate = false
}
onScroll() // execute for first time to setState
const onScrollThrottled = (): void => {
if (!pendingUpdate) {
window.requestAnimationFrame(onScroll)
pendingUpdate = true
}
}
el.addEventListener("scroll", onScrollThrottled)
return (): void => {
el.removeEventListener("scroll", onScrollThrottled)
}
}
return
}, [contentsId])
return [scrollTop, scrollBottom]
}
interface ScrollLockOptions {
doNotLockIfNoScroll: boolean
}
/**
* React hook to prevent scroll events propagating to parent element.
* @param ref the ReactRef of the scrolling container
*/
function useScrollLock<ElementType extends HTMLElement>(
ref: React.RefObject<ElementType>,
opts?: Partial<ScrollLockOptions>
): void {
useEffect(() => {
const el = ref.current
const options: ScrollLockOptions = {
doNotLockIfNoScroll: false,
...opts,
}
if (el) {
function onWheel(ev: WheelEvent): void {
const el = ref.current
if (el) {
const delta = ev.deltaY
const up = delta < 0
const { scrollTop, scrollHeight, offsetHeight } = el
if (
options.doNotLockIfNoScroll &&
scrollHeight <= offsetHeight
) {
return
}
function prevent(): void {
ev.stopPropagation()
ev.preventDefault()
}
if (
!up &&
delta > scrollHeight - offsetHeight - scrollTop
) {
// Scrolling down, but this will take us past the bottom.
el.scrollTop = scrollHeight
return prevent()
} else if (up && -delta > scrollTop) {
// Scrolling up, but this will take us past the top.
el.scrollTop = 0
return prevent()
}
}
}
el.addEventListener("wheel", onWheel as any, {
// We need to be in non-passive mode to be able to cancel the event
passive: false,
})
return (): void => {
if (el) {
el.removeEventListener("wheel", onWheel as any)
}
}
}
return
}, [])
}
|