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-rw-r--r--ext/mixed/js/selector-observer.js255
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diff --git a/ext/mixed/js/selector-observer.js b/ext/mixed/js/selector-observer.js
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-/*
- * Copyright (C) 2020-2021 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 which is used to observe elements matching a selector in specific element.
- */
-class SelectorObserver {
- /**
- * Creates a new instance.
- * @param selector A string CSS selector used to find elements.
- * @param ignoreSelector A string CSS selector used to filter elements, or null for no filtering.
- * @param onAdded A function which is invoked for each element that is added that matches the selector.
- * The signature is (element) => data.
- * @param onRemoved A function which is invoked for each element that is removed, or null.
- * The signature is (element, data) => void.
- * @param onChildrenUpdated A function which is invoked for each element which has its children updated, or null.
- * The signature is (element, data) => void.
- * @param isStale A function which checks if the data is stale for a given element, or null.
- * If the element is stale, it will be removed and potentially re-added.
- * The signature is (element, data) => bool.
- */
- constructor({selector, ignoreSelector=null, onAdded=null, onRemoved=null, onChildrenUpdated=null, isStale=null}) {
- this._selector = selector;
- this._ignoreSelector = ignoreSelector;
- this._onAdded = onAdded;
- this._onRemoved = onRemoved;
- this._onChildrenUpdated = onChildrenUpdated;
- this._isStale = isStale;
- this._observingElement = null;
- this._mutationObserver = new MutationObserver(this._onMutation.bind(this));
- this._elementMap = new Map(); // Map([element => observer]...)
- this._elementAncestorMap = new Map(); // Map([element => Set([observer]...)]...)
- this._isObserving = false;
- }
-
- /**
- * Returns whether or not an element is currently being observed.
- * @returns True if an element is being observed, false otherwise.
- */
- get isObserving() {
- return this._observingElement !== null;
- }
-
- /**
- * Starts DOM mutation observing the target element.
- * @param element The element to observe changes in.
- * @param attributes A boolean for whether or not attribute changes should be observed.
- * @throws An error if element is null.
- * @throws An error if an element is already being observed.
- */
- observe(element, attributes=false) {
- if (element === null) {
- throw new Error('Invalid element');
- }
- if (this.isObserving) {
- throw new Error('Instance is already observing an element');
- }
-
- this._observingElement = element;
- this._mutationObserver.observe(element, {
- attributes: !!attributes,
- childList: true,
- subtree: true
- });
-
- this._onMutation([{
- type: 'childList',
- target: element.parentNode,
- addedNodes: [element],
- removedNodes: []
- }]);
- }
-
- /**
- * Stops observing the target element.
- */
- disconnect() {
- if (!this.isObserving) { return; }
-
- this._mutationObserver.disconnect();
- this._observingElement = null;
-
- for (const observer of this._elementMap.values()) {
- this._removeObserver(observer);
- }
- }
-
- /**
- * Returns an iterable list of [element, data] pairs.
- * @yields A sequence of [element, data] pairs.
- */
- *entries() {
- for (const [element, {data}] of this._elementMap) {
- yield [element, data];
- }
- }
-
- /**
- * Returns an iterable list of data for every element.
- * @yields A sequence of data values.
- */
- *datas() {
- for (const {data} of this._elementMap.values()) {
- yield data;
- }
- }
-
- // Private
-
- _onMutation(mutationList) {
- for (const mutation of mutationList) {
- switch (mutation.type) {
- case 'childList':
- this._onChildListMutation(mutation);
- break;
- case 'attributes':
- this._onAttributeMutation(mutation);
- break;
- }
- }
- }
-
- _onChildListMutation({addedNodes, removedNodes, target}) {
- const selector = this._selector;
- const ELEMENT_NODE = Node.ELEMENT_NODE;
-
- for (const node of removedNodes) {
- const observers = this._elementAncestorMap.get(node);
- if (typeof observers === 'undefined') { continue; }
- for (const observer of observers) {
- this._removeObserver(observer);
- }
- }
-
- for (const node of addedNodes) {
- if (node.nodeType !== ELEMENT_NODE) { continue; }
- if (node.matches(selector)) {
- this._createObserver(node);
- }
- for (const childNode of node.querySelectorAll(selector)) {
- this._createObserver(childNode);
- }
- }
-
- if (
- this._onChildrenUpdated !== null &&
- (addedNodes.length !== 0 || addedNodes.length !== 0)
- ) {
- for (let node = target; node !== null; node = node.parentNode) {
- const observer = this._elementMap.get(node);
- if (typeof observer !== 'undefined') {
- this._onObserverChildrenUpdated(observer);
- }
- }
- }
- }
-
- _onAttributeMutation({target}) {
- const selector = this._selector;
- const observers = this._elementAncestorMap.get(target);
- if (typeof observers !== 'undefined') {
- for (const observer of observers) {
- const element = observer.element;
- if (
- !element.matches(selector) ||
- this._shouldIgnoreElement(element) ||
- this._isObserverStale(observer)
- ) {
- this._removeObserver(observer);
- }
- }
- }
-
- if (target.matches(selector)) {
- this._createObserver(target);
- }
- }
-
- _createObserver(element) {
- if (this._elementMap.has(element) || this._shouldIgnoreElement(element) || this._onAdded === null) { return; }
-
- const data = this._onAdded(element);
- const ancestors = this._getAncestors(element);
- const observer = {element, ancestors, data};
-
- this._elementMap.set(element, observer);
-
- for (const ancestor of ancestors) {
- let observers = this._elementAncestorMap.get(ancestor);
- if (typeof observers === 'undefined') {
- observers = new Set();
- this._elementAncestorMap.set(ancestor, observers);
- }
- observers.add(observer);
- }
- }
-
- _removeObserver(observer) {
- const {element, ancestors, data} = observer;
-
- this._elementMap.delete(element);
-
- for (const ancestor of ancestors) {
- const observers = this._elementAncestorMap.get(ancestor);
- if (typeof observers === 'undefined') { continue; }
-
- observers.delete(observer);
- if (observers.size === 0) {
- this._elementAncestorMap.delete(ancestor);
- }
- }
-
- if (this._onRemoved !== null) {
- this._onRemoved(element, data);
- }
- }
-
- _onObserverChildrenUpdated(observer) {
- this._onChildrenUpdated(observer.element, observer.data);
- }
-
- _isObserverStale(observer) {
- return (this._isStale !== null && this._isStale(observer.element, observer.data));
- }
-
- _shouldIgnoreElement(element) {
- return (this._ignoreSelector !== null && element.matches(this._ignoreSelector));
- }
-
- _getAncestors(node) {
- const root = this._observingElement;
- const results = [];
- while (true) {
- results.push(node);
- if (node === root) { break; }
- node = node.parentNode;
- if (node === null) { break; }
- }
- return results;
- }
-}