mirror of
https://github.com/Polymer/polymer.git
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87 lines
2.8 KiB
HTML
87 lines
2.8 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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<script>
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(function() {
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const DISABLED_ATTR = 'disable-upgrade';
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/**
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* Element class mixin that allows the element to boot up in a non-enabled
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* state when the `disable-upgrade` attribute is present. This mixin is
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* designed to be used with element classes like Polymer.Element that perform
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* initial startup work when they are first connected. When the
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* `disable-upgrade` attribute is removed, if the element is connected, it
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* boots up and "enables" as it otherwise would; if it is not connected, the
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* element boots up when it is next connected.
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*
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* Using `disable-upgrade` with Polymer.Element prevents any data propagation
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* to the element, any element DOM from stamping, or any work done in
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* connected/disconnctedCallback from occuring, but it does not prevent work
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* done in the element constructor.
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*
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* Note, this mixin must be applied on top of any element class that
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* itself implements a `connectedCallback` so that it can control the work
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* done in `connectedCallback`. For example,
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*
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* MyClass = Polymer.DisableUpgradeMixin(class extends BaseClass {...});
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*
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* @mixinFunction
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* @polymer
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* @memberof Polymer
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*/
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Polymer.DisableUpgradeMixin = Polymer.dedupingMixin((base) => {
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return class DisableUpgradeClass extends base {
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static get observedAttributes() {
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return super.observedAttributes.concat(DISABLED_ATTR);
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}
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attributeChangedCallback(name, old, value) {
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if (name == DISABLED_ATTR) {
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if (!this.__dataEnabled && value == null && this.isConnected) {
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super.connectedCallback();
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}
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} else {
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super.attributeChangedCallback(name, old, value);
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}
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}
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__shouldEnable() {
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return this.__dataEnabled || !this.hasAttribute(DISABLED_ATTR);
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}
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// prevent user code in connected from running
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connectedCallback() {
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if (this.__shouldEnable()) {
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super.connectedCallback();
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}
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}
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// prevent element from turning on properties
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_enableProperties() {
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if (this.__shouldEnable()) {
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super._enableProperties();
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}
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}
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// only go if "enabled"
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disconnectedCallback() {
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if (this.__dataEnabled) {
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super.disconnectedCallback();
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}
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}
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}
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});
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})();
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</script>
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