block by ThomasG77 00d60bd321570521c2bf03649280c336

Constrainted drawing within another layer area with OpenLayers (based on official Measure example)

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index.html

<!DOCTYPE html>
<html>
  <head>
    <title>Constrainted drawing (based on official Measure example)</title>
    <link rel="stylesheet" href="https://openlayers.org/en/v4.6.4/css/ol.css" type="text/css">
    <script src='https://npmcdn.com/@turf/turf/turf.min.js'></script>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
    <script src="https://openlayers.org/en/v4.6.4/build/ol.js"></script>
    <style>
      .tooltip {
        position: relative;
        background: rgba(0, 0, 0, 0.5);
        border-radius: 4px;
        color: white;
        padding: 4px 8px;
        opacity: 0.7;
        white-space: nowrap;
      }
      .hidden {
        display: none;
      }
      .tooltip-measure {
        opacity: 1;
        font-weight: bold;
      }
      .tooltip-static {
        background-color: #ffcc33;
        color: black;
        border: 1px solid white;
      }
      .tooltip-measure:before,
      .tooltip-static:before {
        border-top: 6px solid rgba(0, 0, 0, 0.5);
        border-right: 6px solid transparent;
        border-left: 6px solid transparent;
        content: "";
        position: absolute;
        bottom: -6px;
        margin-left: -7px;
        left: 50%;
      }
      .tooltip-static:before {
        border-top-color: #ffcc33;
      }    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <form class="form-inline">
      <input id="checkBox" type="checkbox" checked>
      <label>Activate polygon drawing</label>
    </form>
    <script>
      var raster = new ol.layer.Tile({
        source: new ol.source.OSM()
      });

      var contour = {
        "type": "FeatureCollection",
        "features": [{
          "type": "Feature",
          "geometry": {
            "type": "Polygon",
            "coordinates": [[[-98.82127046585083,38.13872527585437],[-98.8250470161438,38.1400416575801],[-98.8253903388977,38.14351814128884],[-98.82702112197876,38.140851726838264],[-98.83294343948364,38.144159416303694],[-98.83071184158325,38.14858068536492],[-98.82543325424194,38.151314313084185],[-98.82629156112671,38.14507069215483],[-98.82019758224487,38.1480069480217],[-98.81491899490356,38.15323791562108],[-98.8102412223816,38.15273170934594],[-98.8080096244812,38.150808093458124],[-98.80461931228638,38.15185427681277],[-98.80011320114136,38.15020062526921],[-98.79955530166626,38.14571195352295],[-98.80303144454956,38.14226932639963],[-98.81191492080688,38.143079370925676],[-98.81393194198608,38.13808395307731],[-98.82127046585083,38.13872527585437]]]
          },
          "properties": {}
        }]
      };

      var rewindedPolygons = turf.rewind(contour);

      var geoJSONSource = new ol.source.Vector({
        features: new ol.format.GeoJSON({
          featureProjection: 'EPSG:3857'
        }).readFeatures(rewindedPolygons)
      });
      var vectorRestrictionLayer = new ol.layer.Vector({
        source: geoJSONSource,
        style: new ol.style.Style({
          fill: new ol.style.Fill({
            color: 'red'
          })
        })
      });

      var conditionNoModifierKeysWithin = function(mapBrowserEvent) {
        var drawWithin = rewindedPolygons.features.some(feat => {
          return turf.booleanPointInPolygon(
            ol.proj.toLonLat(mapBrowserEvent.coordinate),
            feat
          );
        });

        var originalEvent = mapBrowserEvent.originalEvent;
        return (
          !originalEvent.altKey &&
            !(originalEvent.metaKey || originalEvent.ctrlKey) &&
            !originalEvent.shiftKey && drawWithin);
      };

      var source = new ol.source.Vector();

      var vector = new ol.layer.Vector({
        source: source,
        style: new ol.style.Style({
          fill: new ol.style.Fill({
            color: 'rgba(255, 255, 255, 0.2)'
          }),
          stroke: new ol.style.Stroke({
            color: '#ffcc33',
            width: 2
          }),
          image: new ol.style.Circle({
            radius: 7,
            fill: new ol.style.Fill({
              color: '#ffcc33'
            })
          })
        })
      });


      /**
       * Currently drawn feature.
       * @type {ol.Feature}
       */
      var sketch;


      /**
       * The help tooltip element.
       * @type {Element}
       */
      var helpTooltipElement;


      /**
       * Overlay to show the help messages.
       * @type {ol.Overlay}
       */
      var helpTooltip;


      /**
       * The measure tooltip element.
       * @type {Element}
       */
      var measureTooltipElement;


      /**
       * Overlay to show the measurement.
       * @type {ol.Overlay}
       */
      var measureTooltip;

      /**
       * Message to show when the user is drawing a polygon.
       * @type {string}
       */
      var continuePolygonMsg = 'Click to continue drawing the polygon';

      var avoidDrawingHere = 'You are outside the allowed area to draw';

      /**
       * Handle pointer move.
       * @param {ol.MapBrowserEvent} evt The event.
       */
      var pointerMoveHandler = function(evt) {
        if (evt.dragging) {
          return;
        }
        /** @type {string} */
        var helpMsg = 'Click to start drawing';

        if (sketch) {
          var geom = (sketch.getGeometry());
          var withinSketched = turf.booleanPointInPolygon(ol.proj.toLonLat(evt.coordinate), rewindedPolygons.features[0]);
          if (withinSketched) {
            helpMsg = continuePolygonMsg;
          } else {
            helpMsg = avoidDrawingHere;
          }
        } else {
          var within = rewindedPolygons.features.some(feat => {
            return turf.booleanPointInPolygon(
              ol.proj.toLonLat(evt.coordinate),
              feat
            );
          });
          if (!within) {
            helpMsg = 'You are not allowed to start drawing from here'
          }
        }
        helpTooltipElement.innerHTML = helpMsg;
        helpTooltip.setPosition(evt.coordinate);

        helpTooltipElement.classList.remove('hidden');
      };


      var map = new ol.Map({
        layers: [raster, vectorRestrictionLayer, vector],
        target: 'map',
        view: new ol.View({
          center: [-11000000, 4600000],
          zoom: 16
        })
      });

      var key;
      key = map.on('pointermove', pointerMoveHandler);
      // ol.Observable.unByKey(key);

      map.getViewport().addEventListener('mouseout', function() {
        helpTooltipElement.classList.add('hidden');
      });

      var draw; // global so we can remove it later

      /**
       * Format area output.
       * @param {ol.geom.Polygon} polygon The polygon.
       * @return {string} Formatted area.
       */
      var formatArea = function(polygon) {
        var area = ol.Sphere.getArea(polygon);
        var output;
        if (area > 10000) {
          output = (Math.round(area / 1000000 * 100) / 100) +
              ' ' + 'km<sup>2</sup>';
        } else {
          output = (Math.round(area * 100) / 100) +
              ' ' + 'm<sup>2</sup>';
        }
        return output;
      };

      function addInteraction() {
        var type = 'Polygon';
        draw = new ol.interaction.Draw({
          condition: conditionNoModifierKeysWithin,
          source: source,
          type: type,
          style: new ol.style.Style({
            fill: new ol.style.Fill({
              color: 'rgba(255, 255, 255, 0.2)'
            }),
            stroke: new ol.style.Stroke({
              color: 'rgba(0, 0, 0, 0.5)',
              lineDash: [10, 10],
              width: 2
            }),
            image: new ol.style.Circle({
              radius: 5,
              stroke: new ol.style.Stroke({
                color: 'rgba(0, 0, 0, 0.7)'
              }),
              fill: new ol.style.Fill({
                color: 'rgba(255, 255, 255, 0.2)'
              })
            })
          })
        });
        map.addInteraction(draw);

        createMeasureTooltip();
        createHelpTooltip();

        var listener;
        draw.on('drawstart',
            function(evt) {
              // set sketch
              sketch = evt.feature;
              /** @type {ol.Coordinate|undefined} */
              var tooltipCoord = evt.coordinate;

              listener = sketch.getGeometry().on('change', function(evt) {
                var geom = evt.target;
                var output = formatArea(geom);
                tooltipCoord = geom.getInteriorPoint().getCoordinates();

                measureTooltipElement.innerHTML = output;
                measureTooltip.setPosition(tooltipCoord);
              });
            }, this);

        draw.on('drawend',
            function() {
              measureTooltipElement.className = 'tooltip tooltip-static';
              measureTooltip.setOffset([0, -7]);
              // unset sketch
              sketch = null;
              // unset tooltip so that a new one can be created
              measureTooltipElement = null;
              createMeasureTooltip();
              ol.Observable.unByKey(listener);
            }, this);
      }


      /**
       * Creates a new help tooltip
       */
      function createHelpTooltip() {
        if (helpTooltipElement) {
          helpTooltipElement.parentNode.removeChild(helpTooltipElement);
        }
        helpTooltipElement = document.createElement('div');
        helpTooltipElement.className = 'tooltip hidden';
        helpTooltip = new ol.Overlay({
          element: helpTooltipElement,
          offset: [15, 0],
          positioning: 'center-left'
        });
        map.addOverlay(helpTooltip);
      }


      /**
       * Creates a new measure tooltip
       */
      function createMeasureTooltip() {
        if (measureTooltipElement) {
          measureTooltipElement.parentNode.removeChild(measureTooltipElement);
        }
        measureTooltipElement = document.createElement('div');
        measureTooltipElement.className = 'tooltip tooltip-measure';
        measureTooltip = new ol.Overlay({
          element: measureTooltipElement,
          offset: [0, -15],
          positioning: 'bottom-center'
        });
        map.addOverlay(measureTooltip);
      }

      /**
       * Let user change the geometry type.
       */
      var checkBox = document.getElementById('checkBox');
      checkBox.addEventListener('click', function(e) {
        if (this.checked) {
          map.removeInteraction(draw);
          addInteraction();
          helpTooltipElement.classList.remove('hidden');
          if (Object.keys(key).length === 0) {
            key = map.on('pointermove', pointerMoveHandler);
          }
        } else {
          map.removeInteraction(draw);
          ol.Observable.unByKey(key);
        }
      });

      addInteraction();
    </script>
  </body>
</html>