blob: 2c327091767288af6fa2679954fbedf3b40fb9bc [file] [log] [blame]
/**
* @license
* 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-fixed-panel',
properties: {
floatingDisabled: Boolean,
readyForMeasure: {
type: Boolean,
observer: '_readyForMeasureObserver',
},
keepOnScroll: {
type: Boolean,
value: false,
},
_isMeasured: {
type: Boolean,
value: false,
},
/**
* Initial offset from the top of the document, in pixels.
*/
_topInitial: Number,
/**
* Current offset from the top of the window, in pixels.
*/
_topLast: Number,
_headerHeight: Number,
_headerFloating: {
type: Boolean,
value: false,
},
_observer: {
type: Object,
value: null,
},
_webComponentsReady: Boolean,
},
attached() {
if (this.floatingDisabled) {
return;
}
// Enable content measure unless blocked by param.
if (this.readyForMeasure !== false) {
this.readyForMeasure = true;
}
this.listen(window, 'resize', 'update');
this.listen(window, 'scroll', '_updateOnScroll');
this._observer = new MutationObserver(this.update.bind(this));
this._observer.observe(this.$.header, {childList: true, subtree: true});
},
detached() {
this.unlisten(window, 'scroll', '_updateOnScroll');
this.unlisten(window, 'resize', 'update');
if (this._observer) {
this._observer.disconnect();
}
},
_readyForMeasureObserver(readyForMeasure) {
if (readyForMeasure) {
this.update();
}
},
_computeHeaderClass(headerFloating, topLast) {
const fixedAtTop = this.keepOnScroll && topLast === 0;
return [
headerFloating ? 'floating' : '',
fixedAtTop ? 'fixedAtTop' : '',
].join(' ');
},
unfloat() {
if (this.floatingDisabled) {
return;
}
this.$.header.style.top = '';
this._headerFloating = false;
this.updateStyles({'--header-height': ''});
},
update() {
this.debounce('update', () => {
this._updateDebounced();
}, 100);
},
_updateOnScroll() {
this.debounce('update', () => {
this._updateDebounced();
});
},
_updateDebounced() {
if (this.floatingDisabled) {
return;
}
this._isMeasured = false;
this._maybeFloatHeader();
this._reposition();
},
_getElementTop() {
return this.getBoundingClientRect().top;
},
_reposition() {
if (!this._headerFloating) {
return;
}
const header = this.$.header;
// Since the outer element is relative positioned, can use its top
// to determine how to position the inner header element.
const elemTop = this._getElementTop();
let newTop;
if (this.keepOnScroll && elemTop < 0) {
// Should stick to the top.
newTop = 0;
} else {
// Keep in line with the outer element.
newTop = elemTop;
}
// Initialize top style if it doesn't exist yet.
if (!header.style.top && this._topLast === newTop) {
header.style.top = newTop;
}
if (this._topLast !== newTop) {
if (newTop === undefined) {
header.style.top = '';
} else {
header.style.top = newTop + 'px';
}
this._topLast = newTop;
}
},
_measure() {
if (this._isMeasured) {
return; // Already measured.
}
const rect = this.$.header.getBoundingClientRect();
if (rect.height === 0 && rect.width === 0) {
return; // Not ready for measurement yet.
}
const top = document.body.scrollTop + rect.top;
this._topLast = top;
this._headerHeight = rect.height;
this._topInitial =
this.getBoundingClientRect().top + document.body.scrollTop;
this._isMeasured = true;
},
_isFloatingNeeded() {
return this.keepOnScroll ||
document.body.scrollWidth > document.body.clientWidth;
},
_maybeFloatHeader() {
if (!this._isFloatingNeeded()) {
return;
}
this._measure();
if (this._isMeasured) {
this._floatHeader();
}
},
_floatHeader() {
this.updateStyles({'--header-height': this._headerHeight + 'px'});
this._headerFloating = true;
},
});
})();