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/*
* Copyright (C) 2019 Alex Yatskov <alex@foosoft.net>
* Author: Alex Yatskov <alex@foosoft.net>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
class WindowScroll {
constructor() {
this.animationRequestId = null;
this.animationStartTime = 0;
this.animationStartX = 0;
this.animationStartY = 0;
this.animationEndTime = 0;
this.animationEndX = 0;
this.animationEndY = 0;
this.requestAnimationFrameCallback = (t) => this.onAnimationFrame(t);
}
toY(y) {
this.to(this.x, y);
}
toX(x) {
this.to(x, this.y);
}
to(x, y) {
this.stop();
window.scroll(x, y);
}
animate(x, y, time) {
this.animationStartX = this.x;
this.animationStartY = this.y;
this.animationStartTime = window.performance.now();
this.animationEndX = x;
this.animationEndY = y;
this.animationEndTime = this.animationStartTime + time;
this.animationRequestId = window.requestAnimationFrame(this.requestAnimationFrameCallback);
}
stop() {
if (this.animationRequestId === null) {
return;
}
window.cancelAnimationFrame(this.animationRequestId);
this.animationRequestId = null;
}
onAnimationFrame(time) {
if (time >= this.animationEndTime) {
window.scroll(this.animationEndX, this.animationEndY);
this.animationRequestId = null;
return;
}
const t = WindowScroll.easeInOutCubic((time - this.animationStartTime) / (this.animationEndTime - this.animationStartTime));
window.scroll(
WindowScroll.lerp(this.animationStartX, this.animationEndX, t),
WindowScroll.lerp(this.animationStartY, this.animationEndY, t)
);
this.animationRequestId = window.requestAnimationFrame(this.requestAnimationFrameCallback);
}
get x() {
return window.scrollX || window.pageXOffset;
}
get y() {
return window.scrollY || window.pageYOffset;
}
static easeInOutCubic(t) {
if (t < 0.5) {
return (4.0 * t * t * t);
} else {
t = 1.0 - t;
return 1.0 - (4.0 * t * t * t);
}
}
static lerp(start, end, percent) {
return (end - start) * percent + start;
}
}
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