/
scroll.js
69 lines (60 loc) · 2 KB
/
scroll.js
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(function() {
// Polyfill for scrollIntoViewIfNeeded()
// From https://gist.github.com/jocki84/6ffafd003387179a988e
// License: ISC
if (!Element.prototype.scrollIntoViewIfNeeded) {
Element.prototype.scrollIntoViewIfNeeded = function (centerIfNeeded) {
"use strict";
function makeRange(start, length) {
return {"start": start, "length": length, "end": start + length};
}
function coverRange(inner, outer) {
if (
false === centerIfNeeded ||
(outer.start < inner.end && inner.start < outer.end)
) {
return Math.max(
inner.end - outer.length,
Math.min(outer.start, inner.start)
);
}
return (inner.start + inner.end - outer.length) / 2;
}
function makePoint(x, y) {
return {
"x": x,
"y": y,
"translate": function translate(dX, dY) {
return makePoint(x + dX, y + dY);
}
};
}
function absolute(elem, pt) {
while (elem) {
pt = pt.translate(elem.offsetLeft, elem.offsetTop);
elem = elem.offsetParent;
}
return pt;
}
var target = absolute(this, makePoint(0, 0)),
extent = makePoint(this.offsetWidth, this.offsetHeight),
elem = this.parentNode,
origin;
while (elem instanceof HTMLElement) {
// Apply desired scroll amount.
origin = absolute(elem, makePoint(elem.clientLeft, elem.clientTop));
elem.scrollLeft = coverRange(
makeRange(target.x - origin.x, extent.x),
makeRange(elem.scrollLeft, elem.clientWidth)
);
elem.scrollTop = coverRange(
makeRange(target.y - origin.y, extent.y),
makeRange(elem.scrollTop, elem.clientHeight)
);
// Determine actual scroll amount by reading back scroll properties.
target = target.translate(-elem.scrollLeft, -elem.scrollTop);
elem = elem.parentNode;
}
};
}
})()