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/*
* Copyright (C) 2019-2021 Yomichan Authors
*
* 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 <https://www.gnu.org/licenses/>.
*/
class WindowScroll {
constructor(node) {
this._node = node;
this._animationRequestId = null;
this._animationStartTime = 0;
this._animationStartX = 0;
this._animationStartY = 0;
this._animationEndTime = 0;
this._animationEndX = 0;
this._animationEndY = 0;
this._requestAnimationFrameCallback = this._onAnimationFrame.bind(this);
}
get x() {
return this._node !== null ? this._node.scrollLeft : window.scrollX || window.pageXOffset;
}
get y() {
return this._node !== null ? this._node.scrollTop : window.scrollY || window.pageYOffset;
}
toY(y) {
this.to(this.x, y);
}
toX(x) {
this.to(x, this.y);
}
to(x, y) {
this.stop();
this._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;
}
// Private
_onAnimationFrame(time) {
if (time >= this._animationEndTime) {
this._scroll(this._animationEndX, this._animationEndY);
this._animationRequestId = null;
return;
}
const t = this._easeInOutCubic((time - this._animationStartTime) / (this._animationEndTime - this._animationStartTime));
this._scroll(
this._lerp(this._animationStartX, this._animationEndX, t),
this._lerp(this._animationStartY, this._animationEndY, t)
);
this._animationRequestId = window.requestAnimationFrame(this._requestAnimationFrameCallback);
}
_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);
}
}
_lerp(start, end, percent) {
return (end - start) * percent + start;
}
_scroll(x, y) {
if (this._node !== null) {
this._node.scrollLeft = x;
this._node.scrollTop = y;
} else {
window.scroll(x, y);
}
}
}
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