79 lines
2.5 KiB
HTML
79 lines
2.5 KiB
HTML
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<!--
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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="boot.html">
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<script>
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(function() {
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'use strict';
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// unique global id for deduping mixins.
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let dedupeId = 0;
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/**
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* @constructor
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* @extends {Function}
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*/
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function MixinFunction(){}
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/** @type {(WeakMap | undefined)} */
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MixinFunction.prototype.__mixinApplications;
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/** @type {(Object | undefined)} */
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MixinFunction.prototype.__mixinSet;
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/* eslint-disable valid-jsdoc */
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/**
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* Wraps an ES6 class expression mixin such that the mixin is only applied
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* if it has not already been applied its base argument. Also memoizes mixin
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* applications.
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*
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* @memberof Polymer
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* @template T
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* @param {T} mixin ES6 class expression mixin to wrap
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* @return {T}
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* @suppress {invalidCasts}
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*/
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Polymer.dedupingMixin = function(mixin) {
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let mixinApplications = /** @type {!MixinFunction} */(mixin).__mixinApplications;
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if (!mixinApplications) {
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mixinApplications = new WeakMap();
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/** @type {!MixinFunction} */(mixin).__mixinApplications = mixinApplications;
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}
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// maintain a unique id for each mixin
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let mixinDedupeId = dedupeId++;
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function dedupingMixin(base) {
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let baseSet = /** @type {!MixinFunction} */(base).__mixinSet;
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if (baseSet && baseSet[mixinDedupeId]) {
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return base;
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}
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let map = mixinApplications;
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let extended = map.get(base);
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if (!extended) {
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extended = /** @type {!Function} */(mixin)(base);
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map.set(base, extended);
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}
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// copy inherited mixin set from the extended class, or the base class
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// NOTE: we avoid use of Set here because some browser (IE11)
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// cannot extend a base Set via the constructor.
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let mixinSet = Object.create(/** @type {!MixinFunction} */(extended).__mixinSet || baseSet || null);
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mixinSet[mixinDedupeId] = true;
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/** @type {!MixinFunction} */(extended).__mixinSet = mixinSet;
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return extended;
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}
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return /** @type {T} */ (dedupingMixin);
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};
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/* eslint-enable valid-jsdoc */
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})();
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</script>
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