Qt实现给窗口绘制阴影的示例代码

    this->setWindowFlags(Qt::FramelessWindowHint);
    this->setAttribute(Qt::WA_TranslucentBackground);

void Waiting::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event)
 
    // 1. 初始化一个QPainter对象用来绘制
    // 2. QPainter::Antialiasing，让引擎尽可能的消除锯齿
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
 
    QColor color(0, 0, 0, 50);
    // 此处循环次数为10，目的是绘制宽度为10的阴影
    for(int i=0; i<10; i++)
    {
        // 3. 初始化一个QPainterPath对象
        QPainterPath path;
        // 4. 设置填充规则
        path.setFillRule(Qt::WindingFill);
        // 5. 添加一个矩形
        path.addRect(10-i, 10-i, this->width()-(10-i)*2, this->height()-(10-i)*2);
        // 6. 设置颜色的透明度
        color.setAlpha(150 - qSqrt(i)*50);
        painter.setPen(color);
        // 7. 绘制线路
        painter.drawPath(path);
    }
}

void Waiting::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event)
 
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
 
    QColor color(0, 0, 0, 50);
    for(int i=0; i<10; i++)
    {
        color.setAlpha(150 - qSqrt(i)*50);
        painter.setPen(color);
        // drawRect 绘制矩形
//        painter.drawRect(10-i, 10-i, this->width()-(10-i)*2, this->height()-(10-i)*2);
        // drawRoundedRect 绘制带原角
        painter.drawRoundedRect(10-i, 10-i, this->width()-(10-i)*2, this->height()-(10-i)*2, 20, 20);
    }
}

m_pEffect = new QGraphicsDropShadowEffect(m_background);
m_pEffect->setOffset(0, 0);
m_pEffect->setColor(QColor(QStringLiteral("black")));
m_pEffect->setBlurRadius(30);
m_background->setGraphicsEffect(m_pEffect);