Function nearestPointOnPath

src/label/labelGuideHelper.ts:213–322

* Calculate min distance corresponding point. * This method won't evaluate if point is in the path.

(pt: Point, path: PathProxy, out: Point)

 * This method won't evaluate if point is in the path.
 */
function nearestPointOnPath(pt: Point, path: PathProxy, out: Point) {
    let xi = 0;
    let yi = 0;
    let x0 = 0;
    let y0 = 0;
    let x1;
    let y1;

    let minDist = Infinity;

    const data = path.data;
    const x = pt.x;
    const y = pt.y;

    for (let i = 0; i < data.length;) {
        const cmd = data[i++];

        if (i === 1) {
            xi = data[i];
            yi = data[i + 1];
            x0 = xi;
            y0 = yi;
        }

        let d = minDist;

        switch (cmd) {
            case CMD.M:
                // moveTo 命令重新创建一个新的 subpath, 并且更新新的起点
                // 在 closePath 的时候使用
                x0 = data[i++];
                y0 = data[i++];
                xi = x0;
                yi = y0;
                break;
            case CMD.L:
                d = projectPointToLine(xi, yi, data[i], data[i + 1], x, y, tmpPt, true);
                xi = data[i++];
                yi = data[i++];
                break;
            case CMD.C:
                d = cubicProjectPoint(
                    xi, yi,
                    data[i++], data[i++], data[i++], data[i++], data[i], data[i + 1],
                    x, y, tmpPt
                );

                xi = data[i++];
                yi = data[i++];
                break;
            case CMD.Q:
                d = quadraticProjectPoint(
                    xi, yi,
                    data[i++], data[i++], data[i], data[i + 1],
                    x, y, tmpPt
                );
                xi = data[i++];
                yi = data[i++];