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Custom Interactions

drag5 feature12 vector80 editing2 custom6 interaction5

Example of a custom interaction.

This example demonstrates creating a custom interaction by subclassing ol/interaction/Pointer. Note that the built in interaction ol/interaction/Translate might be a better option for moving features.

main.js
import Feature from 'ol/Feature.js';
import Map from 'ol/Map.js';
import View from 'ol/View.js';
import {LineString, Point, Polygon} from 'ol/geom.js';
import {OGCMapTile, Vector as VectorSource} from 'ol/source.js';
import {
  Pointer as PointerInteraction,
  defaults as defaultInteractions,
} from 'ol/interaction.js';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer.js';

class Drag extends PointerInteraction {
  constructor() {
    super({
      handleDownEvent: handleDownEvent,
      handleDragEvent: handleDragEvent,
      handleMoveEvent: handleMoveEvent,
      handleUpEvent: handleUpEvent,
    });

    /**
     * @type {import("../src/ol/coordinate.js").Coordinate}
     * @private
     */
    this.coordinate_ = null;

    /**
     * @type {string|undefined}
     * @private
     */
    this.cursor_ = 'pointer';

    /**
     * @type {Feature}
     * @private
     */
    this.feature_ = null;

    /**
     * @type {string|undefined}
     * @private
     */
    this.previousCursor_ = undefined;
  }
}

/**
 * @param {import("../src/ol/MapBrowserEvent.js").default} evt Map browser event.
 * @return {boolean} `true` to start the drag sequence.
 */
function handleDownEvent(evt) {
  const map = evt.map;

  const feature = map.forEachFeatureAtPixel(evt.pixel, function (feature) {
    return feature;
  });

  if (feature) {
    this.coordinate_ = evt.coordinate;
    this.feature_ = feature;
  }

  return !!feature;
}

/**
 * @param {import("../src/ol/MapBrowserEvent.js").default} evt Map browser event.
 */
function handleDragEvent(evt) {
  const deltaX = evt.coordinate[0] - this.coordinate_[0];
  const deltaY = evt.coordinate[1] - this.coordinate_[1];

  const geometry = this.feature_.getGeometry();
  geometry.translate(deltaX, deltaY);

  this.coordinate_[0] = evt.coordinate[0];
  this.coordinate_[1] = evt.coordinate[1];
}

/**
 * @param {import("../src/ol/MapBrowserEvent.js").default} evt Event.
 */
function handleMoveEvent(evt) {
  if (this.cursor_) {
    const map = evt.map;
    const feature = map.forEachFeatureAtPixel(evt.pixel, function (feature) {
      return feature;
    });
    const element = evt.map.getTargetElement();
    if (feature) {
      if (element.style.cursor != this.cursor_) {
        this.previousCursor_ = element.style.cursor;
        element.style.cursor = this.cursor_;
      }
    } else if (this.previousCursor_ !== undefined) {
      element.style.cursor = this.previousCursor_;
      this.previousCursor_ = undefined;
    }
  }
}

/**
 * @return {boolean} `false` to stop the drag sequence.
 */
function handleUpEvent() {
  this.coordinate_ = null;
  this.feature_ = null;
  return false;
}

const pointFeature = new Feature(new Point([0, 0]));

const lineFeature = new Feature(
  new LineString([
    [-1e7, 1e6],
    [-1e6, 3e6],
  ]),
);

const polygonFeature = new Feature(
  new Polygon([
    [
      [-3e6, -1e6],
      [-3e6, 1e6],
      [-1e6, 1e6],
      [-1e6, -1e6],
      [-3e6, -1e6],
    ],
  ]),
);

const map = new Map({
  interactions: defaultInteractions().extend([new Drag()]),
  layers: [
    new TileLayer({
      source: new OGCMapTile({
        url: 'https://maps.gnosis.earth/ogcapi/collections/NaturalEarth:raster:HYP_HR_SR_OB_DR/map/tiles/WebMercatorQuad',
        crossOrigin: '',
      }),
    }),
    new VectorLayer({
      source: new VectorSource({
        features: [pointFeature, lineFeature, polygonFeature],
      }),
      style: {
        'icon-src': 'data/icon.png',
        'icon-opacity': 0.95,
        'icon-anchor': [0.5, 46],
        'icon-anchor-x-units': 'fraction',
        'icon-anchor-y-units': 'pixels',
        'stroke-width': 3,
        'stroke-color': [255, 0, 0, 1],
        'fill-color': [0, 0, 255, 0.6],
      },
    }),
  ],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2,
  }),
});
index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Custom Interactions</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>

    <script type="module" src="main.js"></script>
  </body>
</html>
package.json
{
  "name": "custom-interactions",
  "dependencies": {
    "ol": "10.2.1"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}