feat: 绘制多边形终点吸附效果

src/polygon/polygon.ts

@@ -22,17 +22,54 @@ export default class Polygon extends Base {
    * Add points only on click events
    */
   addPoint(cartesian: Cartesian3) {
-    this.points.push(cartesian);
+    let endPoint = cartesian;
+    if (this.points.length > 2) {
+      endPoint = this.getEndPoint(cartesian);
+    }
+    this.points.push(endPoint);
     if (this.points.length === 1) {
       this.onMouseMove();
     }
+    if (this.points.length > 2 && this.comparePositions(this.points[0], endPoint)) {
+      this.finishDrawing();
+    }
+  }
+
+  /**
+   * Compare whether the positions of two points are equal.
+   */
+  comparePositions(point1: Cartesian3, point2: Cartesian3) {
+    const lnglat1 = this.cartesianToLnglat(point1);
+    const lnglat2 = this.cartesianToLnglat(point2);
+    return lnglat1[0] === lnglat2[0] && lnglat1[1] === lnglat2[1];
+  }
+
+  /**
+   * Calculate the distance between two points
+   */
+  calculateDistance(point1: Cartesian3, point2: Cartesian3) {
+    return this.cesium.Cartesian3.distance(point1, point2);
+  }
+
+  /**
+   * get end point
+   */
+  getEndPoint(cartesian: Cartesian3) {
+    let endPoint = cartesian;
+    let distance = this.calculateDistance(this.points[0], cartesian);
+    if (distance < 100) endPoint = this.points[0];
+    return endPoint;
   }
 
   /**
    * Draw a shape based on mouse movement points during the initial drawing.
    */
   updateMovingPoint(cartesian: Cartesian3) {
-    const tempPoints = [...this.points, cartesian];
+    let endPoint = cartesian;
+    if (this.points.length > 2) {
+      endPoint = this.getEndPoint(cartesian);
+    }
+    const tempPoints = [...this.points, endPoint];
     this.setGeometryPoints(tempPoints);
     if (tempPoints.length === 2) {
       this.addTempLine();