startDrawing_(start) {
    const projection = this.getMap().getView().getProjection();
    const stride = getStrideForLayout(this.geometryLayout_);
    while (start.length < stride) {
      start.push(0);
    }
    this.finishCoordinate_ = start;
    if (this.mode_ === 'Point') {
      this.sketchCoords_ = start.slice();
    } else if (this.mode_ === 'Polygon') {
      this.sketchCoords_ = [[start.slice(), start.slice()]];
      this.sketchLineCoords_ = this.sketchCoords_[0];
    } else {
      this.sketchCoords_ = [start.slice(), start.slice()];
    }
    if (this.sketchLineCoords_) {
      this.sketchLine_ = new Feature(new LineString(this.sketchLineCoords_));
    }
    const geometry = this.geometryFunction_(
      this.sketchCoords_,
      undefined,
      projection,
    );
    this.sketchFeature_ = new Feature();
    if (this.geometryName_) {
      this.sketchFeature_.setGeometryName(this.geometryName_);
    }
    this.sketchFeature_.setGeometry(geometry);
    this.updateSketchFeatures_();
    this.dispatchEvent(
      new DrawEvent(DrawEventType.DRAWSTART, this.sketchFeature_),
    );
  }
Start the drawing.
@param {import("../coordinate.js").Coordinate} start Start coordinate.
@private