313 lines
10 KiB
HTML
313 lines
10 KiB
HTML
<!--
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@license
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Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
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This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
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The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
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The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
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Code distributed by Google as part of the polymer project is also
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subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
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-->
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<link rel="import" href="../utils/boot.html">
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<link rel="import" href="../utils/array-splice.html">
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<link rel="import" href="../utils/async.html">
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<script>
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(function() {
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'use strict';
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/**
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* Returns true if `node` is a slot element
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* @param {Node} node Node to test.
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* @return {boolean} Returns true if the given `node` is a slot
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* @private
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*/
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function isSlot(node) {
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return (node.localName === 'slot');
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}
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/**
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* Class that listens for changes (additions or removals) to
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* "flattened nodes" on a given `node`. The list of flattened nodes consists
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* of a node's children and, for any children that are `<slot>` elements,
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* the expanded flattened list of `assignedNodes`.
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* For example, if the observed node has children `<a></a><slot></slot><b></b>`
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* and the `<slot>` has one `<div>` assigned to it, then the flattened
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* nodes list is `<a></a><div></div><b></b>`. If the `<slot>` has other
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* `<slot>` elements assigned to it, these are flattened as well.
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*
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* The provided `callback` is called whenever any change to this list
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* of flattened nodes occurs, where an addition or removal of a node is
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* considered a change. The `callback` is called with one argument, an object
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* containing an array of any `addedNodes` and `removedNodes`.
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*
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* Note: the callback is called asynchronous to any changes
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* at a microtask checkpoint. This is because observation is performed using
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* `MutationObserver` and the `<slot>` element's `slotchange` event which
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* are asynchronous.
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*
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* An example:
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* ```js
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* class TestSelfObserve extends Polymer.Element {
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* static get is() { return 'test-self-observe';}
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* connectedCallback() {
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* super.connectedCallback();
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* this._observer = new Polymer.FlattenedNodesObserver(this, (info) => {
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* this.info = info;
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* });
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* }
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* disconnectedCallback() {
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* super.disconnectedCallback();
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* this._observer.disconnect();
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* }
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* }
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* customElements.define(TestSelfObserve.is, TestSelfObserve);
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* ```
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*
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* @memberof Polymer
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* @summary Class that listens for changes (additions or removals) to
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* "flattened nodes" on a given `node`.
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*/
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class FlattenedNodesObserver {
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/**
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* Returns the list of flattened nodes for the given `node`.
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* This list consists of a node's children and, for any children
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* that are `<slot>` elements, the expanded flattened list of `assignedNodes`.
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* For example, if the observed node has children `<a></a><slot></slot><b></b>`
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* and the `<slot>` has one `<div>` assigned to it, then the flattened
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* nodes list is `<a></a><div></div><b></b>`. If the `<slot>` has other
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* `<slot>` elements assigned to it, these are flattened as well.
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*
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* @param {HTMLElement|HTMLSlotElement} node The node for which to return the list of flattened nodes.
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* @return {Array} The list of flattened nodes for the given `node`.
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*/
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static getFlattenedNodes(node) {
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if (isSlot(node)) {
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node = /** @type {HTMLSlotElement} */(node); // eslint-disable-line no-self-assign
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return node.assignedNodes({flatten: true});
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} else {
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return Array.from(node.childNodes).map((node) => {
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if (isSlot(node)) {
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node = /** @type {HTMLSlotElement} */(node); // eslint-disable-line no-self-assign
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return node.assignedNodes({flatten: true});
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} else {
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return [node];
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}
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}).reduce((a, b) => a.concat(b), []);
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}
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}
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/**
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* @param {Element} target Node on which to listen for changes.
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* @param {?function(!Element, { target: !Element, addedNodes: !Array<!Element>, removedNodes: !Array<!Element> }):void} callback Function called when there are additions
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* or removals from the target's list of flattened nodes.
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*/
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constructor(target, callback) {
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/**
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* @type {MutationObserver}
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* @private
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*/
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this._shadyChildrenObserver = null;
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/**
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* @type {MutationObserver}
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* @private
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*/
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this._nativeChildrenObserver = null;
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this._connected = false;
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/**
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* @type {Element}
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* @private
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*/
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this._target = target;
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this.callback = callback;
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this._effectiveNodes = [];
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this._observer = null;
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this._scheduled = false;
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/**
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* @type {function()}
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* @private
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*/
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this._boundSchedule = () => {
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this._schedule();
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};
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this.connect();
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this._schedule();
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}
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/**
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* Activates an observer. This method is automatically called when
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* a `FlattenedNodesObserver` is created. It should only be called to
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* re-activate an observer that has been deactivated via the `disconnect` method.
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*
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* @return {void}
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*/
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connect() {
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if (isSlot(this._target)) {
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this._listenSlots([this._target]);
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} else if (this._target.children) {
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this._listenSlots(this._target.children);
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if (window.ShadyDOM) {
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this._shadyChildrenObserver =
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ShadyDOM.observeChildren(this._target, (mutations) => {
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this._processMutations(mutations);
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});
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} else {
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this._nativeChildrenObserver =
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new MutationObserver((mutations) => {
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this._processMutations(mutations);
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});
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this._nativeChildrenObserver.observe(this._target, {childList: true});
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}
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}
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this._connected = true;
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}
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/**
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* Deactivates the flattened nodes observer. After calling this method
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* the observer callback will not be called when changes to flattened nodes
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* occur. The `connect` method may be subsequently called to reactivate
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* the observer.
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*
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* @return {void}
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*/
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disconnect() {
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if (isSlot(this._target)) {
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this._unlistenSlots([this._target]);
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} else if (this._target.children) {
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this._unlistenSlots(this._target.children);
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if (window.ShadyDOM && this._shadyChildrenObserver) {
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ShadyDOM.unobserveChildren(this._shadyChildrenObserver);
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this._shadyChildrenObserver = null;
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} else if (this._nativeChildrenObserver) {
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this._nativeChildrenObserver.disconnect();
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this._nativeChildrenObserver = null;
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}
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}
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this._connected = false;
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}
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/**
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* @return {void}
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* @private
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*/
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_schedule() {
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if (!this._scheduled) {
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this._scheduled = true;
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Polymer.Async.microTask.run(() => this.flush());
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}
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}
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/**
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* @param {Array<MutationRecord>} mutations Mutations signaled by the mutation observer
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* @return {void}
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* @private
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*/
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_processMutations(mutations) {
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this._processSlotMutations(mutations);
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this.flush();
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}
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/**
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* @param {Array<MutationRecord>} mutations Mutations signaled by the mutation observer
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* @return {void}
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* @private
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*/
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_processSlotMutations(mutations) {
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if (mutations) {
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for (let i=0; i < mutations.length; i++) {
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let mutation = mutations[i];
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if (mutation.addedNodes) {
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this._listenSlots(mutation.addedNodes);
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}
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if (mutation.removedNodes) {
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this._unlistenSlots(mutation.removedNodes);
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}
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}
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}
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}
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/**
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* Flushes the observer causing any pending changes to be immediately
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* delivered the observer callback. By default these changes are delivered
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* asynchronously at the next microtask checkpoint.
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*
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* @return {boolean} Returns true if any pending changes caused the observer
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* callback to run.
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*/
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flush() {
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if (!this._connected) {
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return false;
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}
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if (window.ShadyDOM) {
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ShadyDOM.flush();
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}
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if (this._nativeChildrenObserver) {
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this._processSlotMutations(this._nativeChildrenObserver.takeRecords());
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} else if (this._shadyChildrenObserver) {
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this._processSlotMutations(this._shadyChildrenObserver.takeRecords());
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}
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this._scheduled = false;
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let info = {
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target: this._target,
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addedNodes: [],
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removedNodes: []
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};
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let newNodes = this.constructor.getFlattenedNodes(this._target);
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let splices = Polymer.ArraySplice.calculateSplices(newNodes,
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this._effectiveNodes);
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// process removals
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for (let i=0, s; (i<splices.length) && (s=splices[i]); i++) {
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for (let j=0, n; (j < s.removed.length) && (n=s.removed[j]); j++) {
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info.removedNodes.push(n);
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}
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}
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// process adds
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for (let i=0, s; (i<splices.length) && (s=splices[i]); i++) {
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for (let j=s.index; j < s.index + s.addedCount; j++) {
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info.addedNodes.push(newNodes[j]);
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}
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}
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// update cache
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this._effectiveNodes = newNodes;
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let didFlush = false;
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if (info.addedNodes.length || info.removedNodes.length) {
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didFlush = true;
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this.callback.call(this._target, info);
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}
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return didFlush;
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}
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/**
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* @param {!Array<Element|Node>|!NodeList<Node>} nodeList Nodes that could change
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* @return {void}
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* @private
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*/
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_listenSlots(nodeList) {
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for (let i=0; i < nodeList.length; i++) {
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let n = nodeList[i];
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if (isSlot(n)) {
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n.addEventListener('slotchange', this._boundSchedule);
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}
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}
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}
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/**
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* @param {!Array<Element|Node>|!NodeList<Node>} nodeList Nodes that could change
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* @return {void}
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* @private
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*/
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_unlistenSlots(nodeList) {
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for (let i=0; i < nodeList.length; i++) {
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let n = nodeList[i];
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if (isSlot(n)) {
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n.removeEventListener('slotchange', this._boundSchedule);
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}
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}
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}
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}
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Polymer.FlattenedNodesObserver = FlattenedNodesObserver;
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})();
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</script>
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