本文从我原先发布在 CSDN 的文章迁移而来，原文链接：https://blog.csdn.net/wang112031/article/details/103281873。

[] 设置不规则的窗体，主要使用 QRegion 类定义可见区域，并通过setMask 函数实现，如下为qt 自带的实例搜索

Shaped Clock Example 即可找到。

ShapedClock::ShapedClock(QWidget *parent)
: QWidget(parent, Qt::FramelessWindowHint | Qt::WindowSystemMenuHint)
{
    //Qt::FramelessWindowHint 设置无边框
    // Qt::WindowSystemMenuHint  WindowCloseButtonHint 两个功能相似，添加一个系统按钮
    QTimer *timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(update()));
    timer->start(1000);

    //添加菜单动作（功能）
    QAction *quitAction = new QAction(tr("E&xit"), this);
    quitAction->setShortcut(tr("Ctrl+Q"));
    connect(quitAction, SIGNAL(triggered()), qApp, SLOT(quit()));
    addAction(quitAction);

    //设置显示规则，显示QWidget::actions() 的菜单
    setContextMenuPolicy(Qt::ActionsContextMenu);
    //设置窗口提示
    setToolTip(tr("Drag the clock with the left mouse button.\n"
    "Use the right mouse button to open a context menu."));
    //设置窗口主题
    setWindowTitle(tr("Shaped Analog Clock"));
}
//! [0]

//! [1]
// 设置无边框后，窗体无法实现按住鼠标右键移动，需要自己继承
// mousePressEvent  mouseMoveEvent 实现
void ShapedClock::mousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        dragPosition = event->globalPos() - frameGeometry().topLeft();
        event->accept();
    }
}
//! [1]

//! [2]
void ShapedClock::mouseMoveEvent(QMouseEvent *event)
{
    if (event->buttons() & Qt::LeftButton) {
        move(event->globalPos() - dragPosition);
        event->accept();
    }
}
//! [2]

//! [3]
void ShapedClock::paintEvent(QPaintEvent *)
{
    static const QPoint hourHand[3] = {
        QPoint(7, 8),
        QPoint(-7, 8),
        QPoint(0, -40)
    };
static const QPoint minuteHand[3] = {
    QPoint(7, 8),
    QPoint(-7, 8),
    QPoint(0, -70)
};

QColor hourColor(127, 0, 127);
QColor minuteColor(0, 127, 127, 191);

int side = qMin(width(), height());
QTime time = QTime::currentTime();

QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing); //设置抗锯齿
painter.translate(width() / 2, height() / 2);
painter.scale(side / 200.0, side / 200.0);

painter.setPen(Qt::NoPen);
painter.setBrush(hourColor);

painter.save();
painter.rotate(30.0 * ((time.hour() + time.minute() / 60.0)));
painter.drawConvexPolygon(hourHand, 3);
painter.restore();

painter.setPen(hourColor);

for (int i = 0; i < 12; ++i) {
    painter.drawLine(88, 0, 96, 0);
    painter.rotate(30.0);
}

painter.setPen(Qt::NoPen);
painter.setBrush(minuteColor);

painter.save();
painter.rotate(6.0 * (time.minute() + time.second() / 60.0));
painter.drawConvexPolygon(minuteHand, 3);
painter.restore();

painter.setPen(minuteColor);

for (int j = 0; j < 60; ++j) {
    if ((j % 5) != 0)
        painter.drawLine(92, 0, 96, 0);
    painter.rotate(6.0);
}
}
//! [3]

//! [4]
void ShapedClock::resizeEvent(QResizeEvent * /* event */)
{
    int side = qMin(width(), height());
    //定义需要可见的区域
    QRegion maskedRegion(width() / 2 - side / 2, height() / 2 - side / 2, side,
    side, QRegion::Ellipse);
    // 通过setMask设置可见的区域
    setMask(maskedRegion);
}
//! [4]

//! [5]
QSize ShapedClock::sizeHint() const
{
    // 设置默认大小
    return QSize(100, 100);
}
//! [5]