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Pop-up dictionary browser extension for language learning. Successor to Yomichan. (PERSONAL FORK)
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JavaScript
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/** * This class is used to control the document focus when a non-body element contains the main scrollbar. * Web browsers will not automatically focus a custom element with the scrollbar on load, which results in * keyboard shortcuts (e.g. arrow keys) not controlling page scroll. Instead, this class will manually * focus a dummy element inside the main content, which gives keyboard scroll focus to that element. */export class DocumentFocusController { /** * Creates a new instance of the class. * @param {?string} autofocusElementSelector A selector string which can be used to specify an element which * should be automatically focused on prepare. */ constructor(autofocusElementSelector = null) { /** @type {?HTMLElement} */ this._autofocusElement = (autofocusElementSelector !== null ? document.querySelector(autofocusElementSelector) : null); /** @type {?HTMLElement} */ this._contentScrollFocusElement = document.querySelector('#content-scroll-focus'); }
/** * Initializes the instance. */ prepare() { window.addEventListener('focus', this._onWindowFocus.bind(this), false); this._updateFocusedElement(false); }
/** * Removes focus from a given element. * @param {HTMLElement} element The element to remove focus from. */ blurElement(element) { if (document.activeElement !== element) { return; } element.blur(); this._updateFocusedElement(false); }
/** */ focusElement() { if (this._autofocusElement !== null && document.activeElement !== this._autofocusElement) { this._autofocusElement.focus({preventScroll: true}); } }
// Private
/** */ _onWindowFocus() { this._updateFocusedElement(false); }
/** * @param {boolean} force */ _updateFocusedElement(force) { const target = this._contentScrollFocusElement; if (target === null) { return; }
const {activeElement} = document; if ( force || activeElement === null || activeElement === document.documentElement || activeElement === document.body ) { // Get selection const selection = window.getSelection(); if (selection === null) { return; } const selectionRanges1 = this._getSelectionRanges(selection);
// Note: This function will cause any selected text to be deselected on Firefox. target.focus({preventScroll: true});
// Restore selection const selectionRanges2 = this._getSelectionRanges(selection); if (!this._areRangesSame(selectionRanges1, selectionRanges2)) { this._setSelectionRanges(selection, selectionRanges1); } } }
/** * @param {Selection} selection * @returns {Range[]} */ _getSelectionRanges(selection) { const ranges = []; for (let i = 0, ii = selection.rangeCount; i < ii; ++i) { ranges.push(selection.getRangeAt(i)); } return ranges; }
/** * @param {Selection} selection * @param {Range[]} ranges */ _setSelectionRanges(selection, ranges) { selection.removeAllRanges(); for (const range of ranges) { selection.addRange(range); } }
/** * @param {Range[]} ranges1 * @param {Range[]} ranges2 * @returns {boolean} */ _areRangesSame(ranges1, ranges2) { const ii = ranges1.length; if (ii !== ranges2.length) { return false; }
for (let i = 0; i < ii; ++i) { const range1 = ranges1[i]; const range2 = ranges2[i]; try { if ( range1.compareBoundaryPoints(Range.START_TO_START, range2) !== 0 || range1.compareBoundaryPoints(Range.END_TO_END, range2) !== 0 ) { return false; } } catch (e) { return false; } }
return true; }}