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// Copyright (C) 2017 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
(function() {
'use strict';
Polymer({
is: 'gr-page-nav',
properties: {
_headerHeight: Number,
},
attached() {
this.listen(window, 'scroll', '_handleBodyScroll');
},
detached() {
this.unlisten(window, 'scroll', '_handleBodyScroll');
},
_handleBodyScroll() {
if (this._headerHeight === undefined) {
let top = this._getOffsetTop(this);
// Don't want to include the element that wraps around the nav, start
// with its parent.
for (let offsetParent = this._getOffsetParent(this.offsetParent);
offsetParent;
offsetParent = this._getOffsetParent(offsetParent)) {
top += this._getOffsetTop(offsetParent);
}
this._headerHeight = top;
}
this.$.nav.classList.toggle('pinned',
this._getScrollY() >= this._headerHeight);
},
/* Functions used for test purposes */
_getOffsetParent(element) {
if (!element || !element.offsetParent) { return ''; }
return element.offsetParent;
},
_getOffsetTop(element) {
return element.offsetTop;
},
_getScrollY() {
return window.scrollY;
},
});
})();
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