129 lines
3.4 KiB
JavaScript
129 lines
3.4 KiB
JavaScript
import Map from '../src/ol/Map.js';
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import View from '../src/ol/View.js';
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import {platformModifierKeyOnly} from '../src/ol/events/condition.js';
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import GeoJSON from '../src/ol/format/GeoJSON.js';
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import {DragBox} from '../src/ol/interaction.js';
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import {Tile as TileLayer, Vector as VectorLayer} from '../src/ol/layer.js';
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import {OSM, Vector as VectorSource} from '../src/ol/source.js';
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import Collection from '../src/ol/Collection.js';
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import Style from '../src/ol/style/Style.js';
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import Fill from '../src/ol/style/Fill.js';
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import Stroke from '../src/ol/style/Stroke.js';
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const vectorSource = new VectorSource({
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url: 'data/geojson/countries.geojson',
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format: new GeoJSON()
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});
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const map = new Map({
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layers: [
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new TileLayer({
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source: new OSM()
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}),
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new VectorLayer({
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source: vectorSource
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})
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],
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target: 'map',
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view: new View({
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center: [0, 0],
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zoom: 2,
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constrainRotation: 16
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})
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});
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const selectedFeatures = new Collection();
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// style features in collection
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const highlightStyle = new Style({
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fill: new Fill({
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color: 'rgba(255,255,255,0.7)'
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}),
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stroke: new Stroke({
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color: '#3399CC',
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width: 3
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})
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});
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selectedFeatures.on('add', function(e) {
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e.element.setStyle(highlightStyle);
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});
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selectedFeatures.on('remove', function(e) {
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e.element.setStyle(undefined);
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});
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// handle clicks
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map.on('singleclick', function(e) {
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selectedFeatures.clear();
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map.forEachFeatureAtPixel(e.pixel, function(f) {
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selectedFeatures.push(f);
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});
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});
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// a DragBox interaction used to select features by drawing boxes
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const dragBox = new DragBox({
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condition: platformModifierKeyOnly
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});
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map.addInteraction(dragBox);
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dragBox.on('boxend', function() {
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// features that intersect the box geometry are added to the
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// collection of selected features
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// if the view is not obliquely rotated the box geometry and
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// its extent are equalivalent so intersecting features can
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// be added directly to the collection
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const rotation = map.getView().getRotation();
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const oblique = rotation % (Math.PI / 2) !== 0;
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const candidateFeatures = oblique ? [] : selectedFeatures;
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const extent = dragBox.getGeometry().getExtent();
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vectorSource.forEachFeatureIntersectingExtent(extent, function(feature) {
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candidateFeatures.push(feature);
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});
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// when the view is obliquely rotated the box extent will
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// exceed its geometry so both the box and the candidate
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// feature geometries are rotated around a common anchor
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// to confirm that, with the box geometry aligned with its
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// extent, the geometries intersect
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if (oblique) {
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const anchor = [0, 0];
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const geometry = dragBox.getGeometry().clone();
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geometry.rotate(-rotation, anchor);
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const extent = geometry.getExtent();
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candidateFeatures.forEach(function(feature) {
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const geometry = feature.getGeometry().clone();
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geometry.rotate(-rotation, anchor);
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if (geometry.intersectsExtent(extent)) {
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selectedFeatures.push(feature);
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}
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});
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}
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});
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// clear selection when drawing a new box and when clicking on the map
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dragBox.on('boxstart', function() {
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selectedFeatures.clear();
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});
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const infoBox = document.getElementById('info');
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selectedFeatures.on(['add', 'remove'], function() {
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const names = selectedFeatures.getArray().map(function(feature) {
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return feature.get('name');
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});
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if (names.length > 0) {
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infoBox.innerHTML = names.join(', ');
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} else {
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infoBox.innerHTML = 'No countries selected';
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}
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});
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