111 lines
4.5 KiB
JavaScript
111 lines
4.5 KiB
JavaScript
/*****************************************************************************
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* Open MCT, Copyright (c) 2014-2018, United States Government
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* as represented by the Administrator of the National Aeronautics and Space
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* Administration. All rights reserved.
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*
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* Open MCT is licensed under the Apache License, Version 2.0 (the
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* "License"); 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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* 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, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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* Open MCT includes source code licensed under additional open source
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* licenses. See the Open Source Licenses file (LICENSES.md) included with
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* this source code distribution or the Licensing information page available
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* at runtime from the About dialog for additional information.
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*****************************************************************************/
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define(
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function () {
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/**
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* Defines the `mct-background-image` directive.
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*
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* Used as an attribute, this will set the `background-image`
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* property to the URL given in its value, but only after that
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* image has loaded; this avoids "flashing" as images change.
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*
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* If the value of `mct-background-image`is falsy, no image
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* will be displayed (immediately.)
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*
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* Optionally, a `filters` attribute may be specified as an
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* object with `brightness` and/or `contrast` properties,
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* whose values are percentages. A value of 100 will make
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* no changes to the image's brightness or contrast.
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*
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* @constructor
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* @memberof platform/features/imagery
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*/
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function MCTBackgroundImage($document) {
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function link(scope, element) {
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// General strategy here:
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// - Keep count of how many images have been requested; this
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// counter will be used as an internal identifier or sorts
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// for each image that loads.
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// - As the src attribute changes, begin loading those images.
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// - When images do load, update the background-image property
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// of the element, but only if a more recently
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// requested image has not already been loaded.
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// The order in which URLs are passed in and the order
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// in which images are actually loaded may be different, so
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// some strategy like this is necessary to ensure that images
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// do not display out-of-order.
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var requested = 0, loaded = 0;
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function updateFilters(filters) {
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var styleValue = filters ?
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Object.keys(filters).map(function (k) {
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return k + "(" + filters[k] + "%)";
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}).join(' ') :
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"";
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element.css('filter', styleValue);
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element.css('webkitFilter', styleValue);
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}
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function nextImage(url) {
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var myCounter = requested,
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image;
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function useImage() {
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if (loaded <= myCounter) {
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loaded = myCounter;
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element.css('background-image', "url('" + url + "')");
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}
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}
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if (!url) {
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loaded = myCounter;
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element.css('background-image', 'none');
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} else {
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image = $document[0].createElement('img');
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image.src = url;
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image.onload = useImage;
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}
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requested += 1;
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}
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scope.$watch('mctBackgroundImage', nextImage);
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scope.$watchCollection('filters', updateFilters);
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}
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return {
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restrict: "A",
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scope: {
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mctBackgroundImage: "=",
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filters: "="
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},
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link: link
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};
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}
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return MCTBackgroundImage;
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}
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);
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