void QMyDialog::paintEvent(QPaintEvent *event)
{
//生成一张位图
QBitmap objBitmap(size());
//QPainter用于在位图上绘画
QPainter painter(&objBitmap);
//填充位图矩形框(用白色填充)
painter.fillRect(rect(),Qt::white);
painter.setBrush(QColor(0,0,0));
//在位图上画圆角矩形(用黑色填充)
painter.drawRoundedRect(this->rect(),5,5);
//画边框 没有效果啊 不是红色
painter.setPen(Qt::red);
painter.drawLine(this->rect().topLeft(),this->rect().topRight());
//使用setmask过滤即可
setMask(objBitmap);
//主窗口缩放最小值
setMinimumSize(m_MinWidth,m_MinHeight);
}