52c943d88e
Diff header scrolls with content and sticks to the top. Implemented custom gr-header wrapper to accomodate this. Bug: Issue 4491 Change-Id: I451ecd4f6c454fd9ab3085ad8f9c5bdd27cb9269
80 lines
2.2 KiB
JavaScript
80 lines
2.2 KiB
JavaScript
// Copyright (C) 2016 The Android Open Source Project
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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(function() {
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'use strict';
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Polymer({
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is: 'gr-header',
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properties: {
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keepOnScroll: {
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type: Boolean,
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},
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_topInitial: Number,
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_topLast: Number,
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_headerHeight: Number,
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},
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attached: function() {
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var rect = this.$.header.getBoundingClientRect();
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this._topInitial = rect.top;
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this._topLast = rect.top;
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this._headerHeight = rect.height;
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this.customStyle['--header-height'] = rect.height + 'px';
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this.updateStyles();
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this.listen(window, 'scroll', '_handleScroll');
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},
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detached: function() {
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this.unlisten(window, 'scroll', '_handleScroll');
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},
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_getScrollY: function() {
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return window.scrollY;
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},
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_handleScrollDebounced: function() {
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var header = this.$.header;
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var scrollY = this._topInitial - this._getScrollY();
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var newTop;
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if (this.keepOnScroll) {
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if (scrollY > 0) {
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// Reposition to imitate natural scrolling.
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newTop = scrollY;
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} else {
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newTop = 0;
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}
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} else if (scrollY > -this._headerHeight ||
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this._topLast < -this._headerHeight) {
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// Allow to scroll away, but ignore when far behind the edge.
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newTop = scrollY;
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} else {
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newTop = -this._headerHeight;
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}
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if (this._topLast !== newTop) {
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if (newTop === undefined) {
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header.style.top = '';
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} else {
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header.style.top = newTop + 'px';
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}
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this._topLast = newTop;
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}
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},
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_handleScroll: function() {
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this.debounce('scroll', this._handleScrollDebounced);
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},
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});
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})();
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