111 lines
3.2 KiB
JavaScript
111 lines
3.2 KiB
JavaScript
/*
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* Copyright (C) 2019-2021 Yomichan Authors
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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class WindowScroll {
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constructor(node) {
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this._node = node;
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this._animationRequestId = null;
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this._animationStartTime = 0;
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this._animationStartX = 0;
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this._animationStartY = 0;
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this._animationEndTime = 0;
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this._animationEndX = 0;
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this._animationEndY = 0;
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this._requestAnimationFrameCallback = this._onAnimationFrame.bind(this);
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}
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get x() {
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return this._node !== null ? this._node.scrollLeft : window.scrollX || window.pageXOffset;
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}
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get y() {
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return this._node !== null ? this._node.scrollTop : window.scrollY || window.pageYOffset;
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}
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toY(y) {
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this.to(this.x, y);
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}
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toX(x) {
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this.to(x, this.y);
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}
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to(x, y) {
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this.stop();
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this._scroll(x, y);
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}
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animate(x, y, time) {
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this._animationStartX = this.x;
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this._animationStartY = this.y;
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this._animationStartTime = window.performance.now();
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this._animationEndX = x;
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this._animationEndY = y;
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this._animationEndTime = this._animationStartTime + time;
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this._animationRequestId = window.requestAnimationFrame(this._requestAnimationFrameCallback);
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}
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stop() {
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if (this._animationRequestId === null) {
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return;
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}
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window.cancelAnimationFrame(this._animationRequestId);
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this._animationRequestId = null;
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}
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// Private
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_onAnimationFrame(time) {
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if (time >= this._animationEndTime) {
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this._scroll(this._animationEndX, this._animationEndY);
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this._animationRequestId = null;
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return;
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}
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const t = this._easeInOutCubic((time - this._animationStartTime) / (this._animationEndTime - this._animationStartTime));
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this._scroll(
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this._lerp(this._animationStartX, this._animationEndX, t),
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this._lerp(this._animationStartY, this._animationEndY, t)
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);
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this._animationRequestId = window.requestAnimationFrame(this._requestAnimationFrameCallback);
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}
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_easeInOutCubic(t) {
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if (t < 0.5) {
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return (4.0 * t * t * t);
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} else {
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t = 1.0 - t;
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return 1.0 - (4.0 * t * t * t);
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}
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}
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_lerp(start, end, percent) {
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return (end - start) * percent + start;
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}
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_scroll(x, y) {
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if (this._node !== null) {
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this._node.scrollLeft = x;
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this._node.scrollTop = y;
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} else {
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window.scroll(x, y);
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}
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}
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}
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