QT
去除默认边框，为界面添加阴影，实现拖动效果。只是示例，没有完成关闭等按钮，根据具体情况添加，可以使用ui设计画一个。

#include <QApplication>
#include <QWidget>
#include <QPoint>
#include <QMouseEvent>
#include <QGraphicsDropShadowEffect>
#include <QVBoxLayout>

class Window:public QWidget
{
    Q_OBJECT
public:
    Window(QWidget* parent=nullptr){
        this->setWindowFlags(Qt::FramelessWindowHint);
        this->setAttribute(Qt::WA_TranslucentBackground);
        // this->setContentsMargins(3,5,5,3); /*左上右下*/

        QGraphicsDropShadowEffect *shadow_effect = new QGraphicsDropShadowEffect(this);
        shadow_effect->setOffset(0, 0);
        shadow_effect->setColor(Qt::black);
        shadow_effect->setBlurRadius(25);

        QWidget* container = new QWidget(this);
        container->setFixedSize(480,360);
        container->setStyleSheet("background-color:red;");
        container->setGraphicsEffect(shadow_effect);
        QVBoxLayout *layout = new QVBoxLayout(this);
        layout->addWidget(container);
        this->setLayout(layout);
    }
protected:
    void mousePressEvent(QMouseEvent *event) override {
        if (event->button() == Qt::LeftButton) {
            /* 计算鼠标点击位置相对于窗口内部的偏移量*/
            m_offset = event->globalPosition().toPoint() - frameGeometry().topLeft();
            event->accept();
        }
    }

    void mouseMoveEvent(QMouseEvent *event) override {
        if (event->buttons() & Qt::LeftButton) {
            /* 移动窗口 */
            move(event->globalPosition().toPoint() - m_offset);
            event->accept();
        }
    }
private:
    QPoint m_offset;
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Window w;
    w.show();
    return a.exec();
}

#include "main.moc"

效果