Function pickEvent

docs/app/js/sanddance-app.js:123721–123724

(evt)

        return this;
    },
    pickEvent (evt) {
        const p = point(evt, this._canvas), o = this._origin;
        return this.pick(this._scene, p[0], p[1], p[0] - o[0], p[1] - o[1]);
    },
    // find the scenegraph item at the current mouse position
    // x, y -- the absolute x, y mouse coordinates on the canvas element
    // gx, gy -- the relative coordinates within the current group