Question

Example on how to use topolis with OpenLayers.

Example showing the integration of topolis with OpenLayers, enabling creating and editing topological geometry. Standard interaction draws edges, snapping to existing edges. Delete an edge by drawing a new edge crossing the one to delete.

main.js

import 'ol/ol.css';
import Feature from 'ol/Feature';
import Map from 'ol/Map';
import MousePosition from 'ol/control/MousePosition';
import View from 'ol/View';
import {
  Circle as CircleStyle,
  Fill,
  Stroke,
  Style,
  Text,
} from 'ol/style';
import {Draw, Snap} from 'ol/interaction';
import {LineString, Point, Polygon} from 'ol/geom';
import {OSM, Vector as VectorSource} from 'ol/source';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';

const raster = new TileLayer({
  source: new OSM(),
});

const nodes = new VectorSource({wrapX: false});
const nodesLayer = new VectorLayer({
  source: nodes,
  style: function (f) {
    const style = new Style({
      image: new CircleStyle({
        radius: 8,
        fill: new Fill({color: 'rgba(255, 0, 0, 0.2)'}),
        stroke: new Stroke({color: 'red', width: 1}),
      }),
      text: new Text({
        text: f.get('node').id.toString(),
        fill: new Fill({color: 'red'}),
        stroke: new Stroke({
          color: 'white',
          width: 3,
        }),
      }),
    });
    return [style];
  },
});

const edges = new VectorSource({wrapX: false});
const edgesLayer = new VectorLayer({
  source: edges,
  style: function (f) {
    const style = new Style({
      stroke: new Stroke({
        color: 'blue',
        width: 1,
      }),
      text: new Text({
        text: f.get('edge').id.toString(),
        fill: new Fill({color: 'blue'}),
        stroke: new Stroke({
          color: 'white',
          width: 2,
        }),
      }),
    });
    return [style];
  },
});

const faces = new VectorSource({wrapX: false});
const facesLayer = new VectorLayer({
  source: faces,
  style: function (f) {
    const style = new Style({
      stroke: new Stroke({
        color: 'black',
        width: 1,
      }),
      fill: new Fill({
        color: 'rgba(0, 255, 0, 0.2)',
      }),
      text: new Text({
        font: 'bold 12px sans-serif',
        text: f.get('face').id.toString(),
        fill: new Fill({color: 'green'}),
        stroke: new Stroke({
          color: 'white',
          width: 2,
        }),
      }),
    });
    return [style];
  },
});

const map = new Map({
  layers: [raster, facesLayer, edgesLayer, nodesLayer],
  target: 'map',
  view: new View({
    center: [-11000000, 4600000],
    zoom: 16,
  }),
});

const topo = topolis.createTopology();

topo.on('addnode', nodeToFeature);
topo.on('removenode', function (e) {
  removeElementFeature(nodes, e);
});
topo.on('addedge', edgeToFeature);
topo.on('modedge', function (e) {
  const feature = edges.getFeatureById(e.id);
  feature.setGeometry(new LineString(e.coordinates));
});
topo.on('removeedge', function (e) {
  removeElementFeature(edges, e);
});
topo.on('addface', faceToFeature);
topo.on('removeface', function (e) {
  removeElementFeature(faces, e);
});

function removeElementFeature(source, element) {
  const feature = source.getFeatureById(element.id);
  source.removeFeature(feature);
}

function nodeToFeature(node) {
  const feature = new Feature({
    geometry: new Point(node.coordinate),
    node: node,
  });
  feature.setId(node.id);
  nodes.addFeature(feature);
}

function edgeToFeature(edge) {
  const feature = new Feature({
    geometry: new LineString(edge.coordinates),
    edge: edge,
  });
  feature.setId(edge.id);
  edges.addFeature(feature);
}

function faceToFeature(face) {
  const coordinates = topo.getFaceGeometry(face);
  const feature = new Feature({
    geometry: new Polygon(coordinates),
    face: face,
  });
  feature.setId(face.id);
  faces.addFeature(feature);
}

function createNode(topo, coord) {
  let node;
  const existingEdge = topo.getEdgeByPoint(coord, 5)[0];
  if (existingEdge) {
    node = topo.modEdgeSplit(existingEdge, coord);
  } else {
    node = topo.addIsoNode(coord);
  }
  return node;
}

function onDrawend(e) {
  const edgeGeom = e.feature.getGeometry().getCoordinates();
  const startCoord = edgeGeom[0];
  const endCoord = edgeGeom[edgeGeom.length - 1];
  let start, end;
  try {
    start = topo.getNodeByPoint(startCoord);
    end = topo.getNodeByPoint(endCoord);
    const edgesAtStart = topo.getEdgeByPoint(startCoord, 5);
    const edgesAtEnd = topo.getEdgeByPoint(endCoord, 5);
    const crossing = topo.getEdgesByLine(edgeGeom);
    if (
      crossing.length === 1 &&
      !start &&
      !end &&
      edgesAtStart.length === 0 &&
      edgesAtEnd.length === 0
    ) {
      topo.remEdgeNewFace(crossing[0]);
      start = crossing[0].start;
      if (start.face) {
        topo.removeIsoNode(start);
      }
      end = crossing[0].end;
      if (end.face) {
        topo.removeIsoNode(end);
      }
      return;
    }
    if (!start) {
      start = createNode(topo, startCoord);
      edgeGeom[0] = start.coordinate;
    }
    if (!end) {
      end = createNode(topo, endCoord);
      edgeGeom[edgeGeom.length - 1] = end.coordinate;
    }
    topo.addEdgeNewFaces(start, end, edgeGeom);
  } catch (e) {
    toastr.warning(e.toString());
  }
}

const draw = new Draw({
  type: 'LineString',
});
draw.on('drawend', onDrawend);
map.addInteraction(draw);
const snap = new Snap({
  source: edges,
});
map.addInteraction(snap);
map.addControl(new MousePosition());

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>topolis integration</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,URL,TextDecoder,Number.isInteger"></script>
    <script src="https://unpkg.com/topolis@0.2.5/dist/topolis.js"></script>
    <script src="./resources/jquery-3.5.1.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/toastr.js/2.1.3/toastr.min.js"></script>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/toastr.js/2.1.3/toastr.min.css">
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "topolis",
  "dependencies": {
    "ol": "7.1.0"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}