web/_javascript/utils/smooth-scroll.js
2021-12-07 16:26:26 +08:00

93 lines
3.1 KiB
JavaScript

/*
Safari doesn't support CSS `scroll-behavior: smooth`,
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 REM = 16; /* 16px */
const $topbarTitle = $("#topbar-title");
const topbarHeight = $("#topbar-wrapper").outerHeight();
const SCROLL_MARK = "scroll-focus";
$("a[href*='#']")
.not("[href='#']")
.not("[href='#0']")
.click(function(event) {
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);
if (typeof $target !== "undefined") {
event.preventDefault();
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;
if (destOffset < curOffset) { // scroll up
if (toFootnoteRef) {
// Avoid the top-bar covering `fnref` when scrolling up
// because `fnref` has no `%anchor`(see: module.scss) style.
destOffset -= (topbarHeight + REM / 2);
}
if (isAnchor && $topbarTitle.is(":hidden")) {
destOffset += topbarHeight;
}
} else { // scroll down
if (!isAnchor && !toFootnote) { // the ToC item
destOffset += topbarHeight;
}
}
$("html,body").animate({
scrollTop: destOffset
}, 800, () => {
// const $target = $($target);
$target.focus();
/* clean up old scroll mark */
if ($(`[${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) {
$target.attr(SCROLL_MARK, true);
}
if ($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 */
}
});
}
}
}
}); /* click() */
});