Function scrollHandler

ui/src/common/ScrollUpButton.tsx:8–15

()

    const [state, setState] = React.useState({display: 'none', opacity: 0});
    React.useEffect(() => {
        const scrollHandler = () => {
            const currentScrollPos = Math.max(window.pageYOffset - 1000, 0);
            const opacity = Math.min(currentScrollPos / 1000, 1);
            const nextState = {display: currentScrollPos > 0 ? 'inherit' : 'none', opacity};
            if (state.display !== nextState.display || state.opacity !== nextState.opacity) {
                setState(nextState);
            }
        };
        window.addEventListener('scroll', scrollHandler);
        return () => window.removeEventListener('scroll', scrollHandler);
    }, []);