111 lines
3.6 KiB
JavaScript
111 lines
3.6 KiB
JavaScript
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/*
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* Copyright (C) 2020 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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/**
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* This class is used to control the document focus when a non-body element contains the main scrollbar.
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* Web browsers will not automatically focus a custom element with the scrollbar on load, which results in
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* keyboard shortcuts (e.g. arrow keys) not controlling page scroll. Instead, this class will manually
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* focus a dummy element inside the main content, which gives keyboard scroll focus to that element.
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*/
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class DocumentFocusController {
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constructor() {
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this._contentScrollFocusElement = document.querySelector('#content-scroll-focus');
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}
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prepare() {
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window.addEventListener('focus', this._onWindowFocus.bind(this), false);
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this._updateFocusedElement(false);
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}
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blurElement(element) {
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if (document.activeElement !== element) { return; }
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element.blur();
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this._updateFocusedElement(false);
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}
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// Private
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_onWindowFocus() {
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this._updateFocusedElement(false);
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}
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_updateFocusedElement(force) {
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const target = this._contentScrollFocusElement;
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if (target === null) { return; }
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const {activeElement} = document;
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if (
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force ||
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activeElement === null ||
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activeElement === document.documentElement ||
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activeElement === document.body
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) {
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// Get selection
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const selection = window.getSelection();
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const selectionRanges1 = this._getSelectionRanges(selection);
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// Note: This function will cause any selected text to be deselected on Firefox.
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target.focus({preventScroll: true});
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// Restore selection
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const selectionRanges2 = this._getSelectionRanges(selection);
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if (!this._areRangesSame(selectionRanges1, selectionRanges2)) {
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this._setSelectionRanges(selection, selectionRanges1);
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}
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}
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}
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_getSelectionRanges(selection) {
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const ranges = [];
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for (let i = 0, ii = selection.rangeCount; i < ii; ++i) {
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ranges.push(selection.getRangeAt(i));
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}
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return ranges;
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}
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_setSelectionRanges(selection, ranges) {
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selection.removeAllRanges();
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for (const range of ranges) {
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selection.addRange(range);
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}
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}
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_areRangesSame(ranges1, ranges2) {
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const ii = ranges1.length;
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if (ii !== ranges2.length) {
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return false;
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}
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for (let i = 0; i < ii; ++i) {
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const range1 = ranges1[i];
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const range2 = ranges2[i];
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try {
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if (
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range1.compareBoundaryPoints(Range.START_TO_START, range2) !== 0 ||
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range1.compareBoundaryPoints(Range.END_TO_END, range2) !== 0
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) {
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return false;
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}
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} catch (e) {
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return false;
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}
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}
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return true;
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}
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}
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