web/_javascript/modules/components/topbar-switcher.js

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/**
* Hide Header on scroll down
*/
import ScrollHelper from './utils/scroll-helper';
const $searchInput = $('#search-input');
const delta = ScrollHelper.getTopbarHeight();
let didScroll;
let lastScrollTop = 0;
function hasScrolled() {
let st = $(window).scrollTop();
/* Make sure they scroll more than delta */
if (Math.abs(lastScrollTop - st) <= delta) {
return;
}
if (st > lastScrollTop) {
/* Scroll down */
ScrollHelper.hideTopbar();
if ($searchInput.is(':focus')) {
$searchInput.trigger('blur'); /* remove focus */
}
} else {
/* Scroll up */
// has not yet scrolled to the bottom of the screen, that is, there is still space for scrolling
if (st + $(window).height() < $(document).height()) {
if (ScrollHelper.hasScrollUpTask()) {
return;
}
if (ScrollHelper.topbarLocked()) {
// avoid redundant scroll up event from smooth scrolling
ScrollHelper.unlockTopbar();
} else {
if (ScrollHelper.orientationLocked()) {
// avoid device auto scroll up on orientation change
ScrollHelper.unLockOrientation();
} else {
ScrollHelper.showTopbar();
}
}
}
}
lastScrollTop = st;
} // hasScrolled()
function handleLandscape() {
if ($(window).scrollTop() === 0) {
return;
}
ScrollHelper.lockOrientation();
ScrollHelper.hideTopbar();
}
export function switchTopbar() {
const orientation = screen.orientation;
if (orientation) {
orientation.onchange = () => {
const type = orientation.type;
if (type === 'landscape-primary' || type === 'landscape-secondary') {
handleLandscape();
}
};
} else {
// for the browsers that not support `window.screen.orientation` API
$(window).on('orientationchange', () => {
if ($(window).width() < $(window).height()) {
// before rotating, it is still in portrait mode.
handleLandscape();
}
});
}
$(window).on('scroll', () => {
if (didScroll) {
return;
}
didScroll = true;
});
setInterval(() => {
if (didScroll) {
hasScrolled();
didScroll = false;
}
}, 250);
}