return last snapTo feature

src/ol/events/SnapEvent.js

@@ -0,0 +1,51 @@
+/**
+ * @module ol/events/SnapEvent
+ */
+import Event from './Event.js';
+
+/**
+ * @enum {string}
+ */
+export const SnapEventType = {
+  /**
+   * Triggered upon snapping to vertex or edge
+   * @event SnapEvent#snap
+   * @api
+   */
+  SNAP: 'snap',
+};
+
+/**
+ * @classdesc
+ * Events emitted by {@link module:ol/interaction/Snap~Snap} instances are instances of this
+ */
+export class SnapEvent extends Event {
+  /**
+   * @param {SnapEventType} type Type.
+   * @param {Object} options Options.
+   * @param {import("../coordinate.js").Coordinate} options.vertex The snapped vertex.
+   * @param {import("../coordinate.js").Coordinate} options.vertexPixel The pixel of the snapped vertex.
+   * @param {import("../Feature.js").default} options.feature The feature being snapped.
+   */
+  constructor(type, options) {
+    super(type);
+    /**
+     * The Map coordinate of the snapped point.
+     * @type {import("../coordinate.js").Coordinate}
+     * @api
+     */
+    this.vertex = options.vertex;
+    /**
+     * The Map pixel of the snapped point.
+     * @type {Array<number>&Array<number>}
+     * @api
+     */
+    this.vertexPixel = options.vertexPixel;
+    /**
+     * The feature closest to the snapped point.
+     * @type {import("../Feature.js").default<import("../geom/Geometry.js").default>}
+     * @api
+     */
+    this.feature = options.feature;
+  }
+}

src/ol/interaction/Snap.js

@@ -7,6 +7,7 @@ import PointerInteraction from './Pointer.js';
 import RBush from '../structs/RBush.js';
 import VectorEventType from '../source/VectorEventType.js';
 import {FALSE, TRUE} from '../functions.js';
+import {SnapEvent, SnapEventType} from '../events/SnapEvent.js';
 import {boundingExtent, buffer, createEmpty} from '../extent.js';
 import {
   closestOnCircle,
@@ -27,6 +28,7 @@ import {listen, unlistenByKey} from '../events.js';
  * @typedef {Object} Result
  * @property {import("../coordinate.js").Coordinate|null} vertex Vertex.
  * @property {import("../pixel.js").Pixel|null} vertexPixel VertexPixel.
+ * @property {import("../Feature.js").default|null} feature Feature.
  */
 
 /**
@@ -70,6 +72,16 @@ function getFeatureFromEvent(evt) {
 
 const tempSegment = [];
 
+/***
+ * @template Return
+ * @typedef {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default, Return> &
+ *   import("../Observable").OnSignature<import("../ObjectEventType").Types|
+ *     'change:active', import("../Object").ObjectEvent, Return> &
+ *   import("../Observable").OnSignature<'snap', SnapEvent, Return> &
+ *   import("../Observable").CombinedOnSignature<import("../Observable").EventTypes|import("../ObjectEventType").Types|
+ *     'change:active'|'snap', Return>} SnapOnSignature
+ */
+
 /**
  * @classdesc
  * Handles snapping of vector features while modifying or drawing them.  The
@@ -91,6 +103,7 @@ const tempSegment = [];
  *
  *     map.addInteraction(snap);
  *
+ * @fires SnapEvent
  * @api
  */
 class Snap extends PointerInteraction {
@@ -114,6 +127,21 @@ class Snap extends PointerInteraction {
 
     super(pointerOptions);
 
+    /***
+     * @type {SnapOnSignature<import("../events").EventsKey>}
+     */
+    this.on;
+
+    /***
+     * @type {SnapOnSignature<import("../events").EventsKey>}
+     */
+    this.once;
+
+    /***
+     * @type {SnapOnSignature<void>}
+     */
+    this.un;
+
     /**
      * @type {import("../source/Vector.js").default|null}
      * @private
@@ -263,12 +291,20 @@ class Snap extends PointerInteraction {
   /**
    * @param {import("../MapBrowserEvent.js").default} evt Map browser event.
    * @return {boolean} `false` to stop event propagation.
+   * @api
    */
   handleEvent(evt) {
     const result = this.snapTo(evt.pixel, evt.coordinate, evt.map);
     if (result) {
       evt.coordinate = result.vertex.slice(0, 2);
       evt.pixel = result.vertexPixel;
+      this.dispatchEvent(
+        new SnapEvent(SnapEventType.SNAP, {
+          vertex: evt.coordinate,
+          vertexPixel: evt.pixel,
+          feature: result.feature,
+        })
+      );
     }
     return super.handleEvent(evt);
   }
@@ -432,14 +468,14 @@ class Snap extends PointerInteraction {
     );
 
     const segments = this.rBush_.getInExtent(box);
-
     const segmentsLength = segments.length;
     if (segmentsLength === 0) {
       return null;
     }
 
     let closestVertex;
     let minSquaredDistance = Infinity;
+    let closestFeature;
 
     const squaredPixelTolerance = this.pixelTolerance_ * this.pixelTolerance_;
     const getResult = () => {
@@ -453,6 +489,7 @@ class Snap extends PointerInteraction {
               Math.round(vertexPixel[0]),
               Math.round(vertexPixel[1]),
             ],
+            feature: closestFeature,
           };
         }
       }
@@ -469,6 +506,7 @@ class Snap extends PointerInteraction {
             if (delta < minSquaredDistance) {
               closestVertex = vertex;
               minSquaredDistance = delta;
+              closestFeature = segmentData.feature;
             }
           });
         }