web/_javascript/utils/smooth-scroll.js

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/*
Safari doesn't support CSS `scroll-behavior: smooth`,
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so here is a compatible solution for all browser to smooth scrolling
See: <https://css-tricks.com/snippets/jquery/smooth-scrolling/>
Warning: It must be called after all `<a>` tags (e.g., the dynamic TOC) are ready.
*/
$(function() {
const $topbarWrapper = $("#topbar-wrapper");
const topbarHeight = $topbarWrapper.outerHeight();
const $topbarTitle = $("#topbar-title");
const ATTR_TOC_SCROLLING = "toc-scrolling-up";
const SCROLL_MARK = "scroll-focus";
const REM = 16; // in pixels
let tocScrollUpCount = 0;
$("a[href*='#']")
.not("[href='#']")
.not("[href='#0']")
.click(function(event) {
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if (this.pathname.replace(/^\//, "") === location.pathname.replace(/^\//, "")) {
if (location.hostname === this.hostname) {
const hash = decodeURI(this.hash);
let toFootnoteRef = RegExp(/^#fnref:/).test(hash);
let toFootnote = toFootnoteRef? false : RegExp(/^#fn:/).test(hash);
let selector = hash.includes(":") ? hash.replace(/\:/g, "\\:") : hash;
let $target = $(selector);
let parent = $(this).parent().prop("tagName");
let isAnchor = RegExp(/^H\d/).test(parent);
let isMobileViews = !$topbarTitle.is(":hidden");
if (typeof $target !== "undefined") {
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event.preventDefault();
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if (history.pushState) { /* add hash to URL */
history.pushState(null, null, hash);
}
let curOffset = isAnchor? $(this).offset().top : $(window).scrollTop();
let destOffset = $target.offset().top -= REM / 2;
if (destOffset < curOffset) { // scroll up
if (!isAnchor && !toFootnote) { // trigger by ToC item
if (!isMobileViews) { // on desktop/tablet screens
$topbarWrapper.removeClass("topbar-down").addClass("topbar-up");
// Send message to `${JS_ROOT}/commons/topbar-switch.js`
$topbarWrapper.attr(ATTR_TOC_SCROLLING, true);
tocScrollUpCount += 1;
}
}
if ((isAnchor || toFootnoteRef) && isMobileViews) {
destOffset -= topbarHeight;
}
}
$("html").animate({
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scrollTop: destOffset
}, 500, () => {
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$target.focus();
/* clean up old scroll mark */
if ($(`[${SCROLL_MARK}=true]`).length) {
$(`[${SCROLL_MARK}=true]`).attr(SCROLL_MARK, false);
}
/* Clean :target links */
if ($(":target").length) { /* element that visited by the URL with hash */
$(":target").attr(SCROLL_MARK, false);
}
/* set scroll mark to footnotes */
if (toFootnote || toFootnoteRef) {
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$target.attr(SCROLL_MARK, true);
}
if ($target.is(":focus")) { /* Checking if the target was focused */
return false;
} else {
$target.attr("tabindex", "-1"); /* Adding tabindex for elements not focusable */
$target.focus(); /* Set focus again */
}
if (typeof $topbarWrapper.attr(ATTR_TOC_SCROLLING) !== "undefined") {
tocScrollUpCount -= 1;
if (tocScrollUpCount <= 0) {
$topbarWrapper.attr(ATTR_TOC_SCROLLING, "false");
}
}
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});
}
}
}
}); /* click() */
});