Shadcn UI Scroll Area with Overflow Fading Support

scroll-area.tsx

import { cn } from '@/lib/utils';
import * as ScrollAreaPrimitive from '@radix-ui/react-scroll-area';
import * as React from 'react';
import { useEffect, useRef, useState } from 'react';

const ScrollArea = React.forwardRef<
    React.ComponentRef<typeof ScrollAreaPrimitive.Root>,
    React.ComponentPropsWithoutRef<typeof ScrollAreaPrimitive.Root> & { fade?: boolean }
>(({ className, fade, children, ...props }, ref) => {
    const viewPortRef = useRef<HTMLDivElement | null>(null);

    const [showTopFade, setShowTopFade] = useState(false);

    const [showBottomFade, setShowBottomFade] = useState(false);

    useEffect(() => {
        if (!fade) {
            return;
        }

        const el = viewPortRef.current;

        if (!el) {
            return;
        }

        const handleScroll = () => {
            const { scrollTop, scrollHeight, clientHeight } = el;

            setShowTopFade(scrollTop > 0);

            setShowBottomFade(scrollTop + clientHeight < scrollHeight);
        };

        handleScroll();

        el.addEventListener('scroll', handleScroll);

        return () => {
            el.removeEventListener('scroll', handleScroll);
        };
    }, [fade]);

    return (
        <ScrollAreaPrimitive.Root
            data-slot="scroll-area"
            ref={ref}
            className={cn('relative overflow-hidden', className)}
            {...props}
        >
            <ScrollAreaPrimitive.Viewport
                data-slot="scroll-area-viewport"
                ref={viewPortRef}
                className="h-full w-full rounded-[inherit]"
            >
                {fade && (
                    <>
                        <div
                            data-slot="scroll-area-top-fade"
                            className={cn(
                                'pointer-events-none absolute top-0 right-0 left-0 h-6 bg-gradient-to-b from-white to-transparent transition-opacity duration-200',
                                showTopFade ? 'opacity-100' : 'opacity-0',
                            )}
                        />
                        <div
                            data-slot="scroll-area-bottom-fade"
                            className={cn(
                                'pointer-events-none absolute right-0 bottom-0 left-0 h-6 bg-gradient-to-t from-white to-transparent transition-opacity duration-200',
                                showBottomFade ? 'opacity-100' : 'opacity-0',
                            )}
                        />
                    </>
                )}

                {children}
            </ScrollAreaPrimitive.Viewport>
            <ScrollBar />
            <ScrollAreaPrimitive.Corner />
        </ScrollAreaPrimitive.Root>
    );
});
ScrollArea.displayName = ScrollAreaPrimitive.Root.displayName;

const ScrollBar = React.forwardRef<
    React.ComponentRef<typeof ScrollAreaPrimitive.ScrollAreaScrollbar>,
    React.ComponentPropsWithoutRef<typeof ScrollAreaPrimitive.ScrollAreaScrollbar>
>(({ className, orientation = 'vertical', ...props }, ref) => (
    <ScrollAreaPrimitive.ScrollAreaScrollbar
        ref={ref}
        data-slot="scroll-area-scrollbar"
        orientation={orientation}
        className={cn(
            'flex touch-none transition-colors select-none',
            orientation === 'vertical' && 'h-full w-2.5 border-l border-l-transparent p-[1px]',
            orientation === 'horizontal' && 'h-2.5 flex-col border-t border-t-transparent p-[1px]',
            className,
        )}
        {...props}
    >
        <ScrollAreaPrimitive.ScrollAreaThumb className="relative flex-1 rounded-full bg-border" />
    </ScrollAreaPrimitive.ScrollAreaScrollbar>
));
ScrollBar.displayName = ScrollAreaPrimitive.ScrollAreaScrollbar.displayName;

export { ScrollArea, ScrollBar };