如何擦除/移除QGraphicPathItem的特定部分？

QPainterPath newPath;
// 根据需要构建新路径，只包含想要保留的部分
newPath.addPath(graphicPathItem->path(), Qt::ReplaceAction);

graphicPathItem->setPath(newPath);

QPainter painter(view);
// 绘制不需要的部分，覆盖掉
painter.setCompositionMode(QPainter::CompositionMode_Clear);
painter.fillRect(unwantedArea, Qt::transparent);
painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
// 绘制原始图形
graphicPathItem->paint(&painter, option, widget);

QPainterPath path = graphicPathItem->path();
QPainterPathStroker stroker;
QPainterPath splitPath = stroker.createStroke(path);

// 找到并移除不需要的部分
QPainterPathIterator it(splitPath);
while (!it.isDone()) {
    QPainterPathElement elem = it.currentElement();
    if (/* 判断 elem 是否在不需要的部分 */) {
        it.removeCurrent();
    }
    it.next();
}

graphicPathItem->setPath(splitPath);