documentation/node_modules/@docusaurus/theme-common/lib/hooks/useHideableNavbar.js

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
import { useState, useCallback, useRef } from 'react';
import { useLocationChange } from '../utils/useLocationChange';
import { useScrollPosition } from '../utils/scrollUtils';
/**
 * Wires the imperative logic of a hideable navbar.
 * @param hideOnScroll If `false`, this hook is basically a no-op.
 */
export function useHideableNavbar(hideOnScroll) {
    const [isNavbarVisible, setIsNavbarVisible] = useState(hideOnScroll);
    const isFocusedAnchor = useRef(false);
    const navbarHeight = useRef(0);
    const navbarRef = useCallback((node) => {
        if (node !== null) {
            navbarHeight.current = node.getBoundingClientRect().height;
        }
    }, []);
    useScrollPosition(({ scrollY: scrollTop }, lastPosition) => {
        if (!hideOnScroll) {
            return;
        }
        // Needed mostly for handling rubber band scrolling.
        // See https://github.com/facebook/docusaurus/pull/5721
        if (scrollTop < navbarHeight.current) {
            setIsNavbarVisible(true);
            return;
        }
        if (isFocusedAnchor.current) {
            isFocusedAnchor.current = false;
            return;
        }
        const lastScrollTop = lastPosition?.scrollY;
        const documentHeight = document.documentElement.scrollHeight - navbarHeight.current;
        const windowHeight = window.innerHeight;
        if (lastScrollTop && scrollTop >= lastScrollTop) {
            setIsNavbarVisible(false);
        }
        else if (scrollTop + windowHeight < documentHeight) {
            setIsNavbarVisible(true);
        }
    });
    useLocationChange((locationChangeEvent) => {
        if (!hideOnScroll) {
            return;
        }
        // See https://github.com/facebook/docusaurus/pull/8059#issuecomment-1239639480
        const currentHash = locationChangeEvent.location.hash;
        const currentHashAnchor = currentHash
            ? document.getElementById(currentHash.substring(1))
            : undefined;
        if (currentHashAnchor) {
            isFocusedAnchor.current = true;
            setIsNavbarVisible(false);
            return;
        }
        setIsNavbarVisible(true);
    });
    return { navbarRef, isNavbarVisible };
}
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