展示：

代码实现：

// 鼠标按下事件(记录拉伸窗口或移动窗口时的起始坐标（左上角）)
void framelessWidget::mousePressEvent(QMouseEvent *event)
{if(event->button() == Qt::LeftButton){mousePressed = true;
#if (QT_VERSION >= QT_VERSION_CHECK(6,0,0))lastPos = event->globalPosition().toPoint() - this->frameGeometry().topLeft();
#elselastPos = event->globalPos() - this->frameGeometry().topLeft();
#endif}
}// 鼠标移动事件
void framelessWidget::mouseMoveEvent(QMouseEvent *event)
{if(event->buttons() == Qt::NoButton)mousePressed = false;if(!mousePressed){ // 鼠标没按下移动，更新鼠标位置状态mouseState = 0;if(!maximized && abs(event->pos().x() - ui->mainWidget->pos().x()) < 5)mouseState |= AT_LEFT;if(!maximized && abs(event->pos().y() - ui->mainWidget->pos().y()) < 5)mouseState |= AT_TOP;if(!maximized && abs(event->pos().x() - ui->mainWidget->pos().x() - ui->mainWidget->width()) < 5)mouseState |= AT_RIGHT;if(!maximized && abs(event->pos().y() - ui->mainWidget->pos().y() - ui->mainWidget->height()) < 5)mouseState |= AT_BOTTOM;if(mouseState == AT_TOP_LEFT  || mouseState == AT_BOTTOM_RIGHT)setCursor(Qt::SizeFDiagCursor);else if(mouseState == AT_TOP_RIGHT || mouseState == AT_BOTTOM_LEFT)setCursor(Qt::SizeBDiagCursor);else if(mouseState & (AT_LEFT | AT_RIGHT))setCursor(Qt::SizeHorCursor);else if(mouseState & (AT_TOP | AT_BOTTOM))setCursor(Qt::SizeVerCursor);elseunsetCursor();}else{ //鼠标按下移动if(mouseState == 0){if(maximized){qreal wRatio = (double)event->pos().x() / (double)ui->mainWidget->width();controlWindowScale();
#if (QT_VERSION >= QT_VERSION_CHECK(6,0,0))this->move(QPoint(event->globalPosition().x() - ui->mainWidget->width() * wRatio, -30));
#elsethis->move(QPoint(event->globalPos().x() - ui->mainWidget->width() * wRatio, -30));
#endiflastPos = QPoint(ui->mainWidget->width() * wRatio, event->pos().y());}else
#if (QT_VERSION >= QT_VERSION_CHECK(6,0,0))this->move(event->globalPosition().toPoint() - lastPos);
#elsethis->move(event->globalPos() - lastPos);
#endif}else{
#if (QT_VERSION >= QT_VERSION_CHECK(6,0,0))QPoint d = event->globalPosition().toPoint() - frameGeometry().topLeft() - lastPos;
#elseQPoint d = event->globalPos() - frameGeometry().topLeft() - lastPos;
#endifif(mouseState & AT_LEFT){this->move(this->frameGeometry().x() + d.x(), this->frameGeometry().y());this->resize(this->width() - d.x(), this->height());}if(mouseState & AT_RIGHT){this->resize(this->width() + d.x(), this->height());}if(mouseState & AT_TOP){this->move(this->frameGeometry().x(), this->frameGeometry().y() + d.y());this->resize(this->width(), this->height() - d.y());}if(mouseState & AT_BOTTOM){this->resize(this->width(), this->height() + d.y());}}
#if (QT_VERSION >= QT_VERSION_CHECK(6,0,0))lastPos = event->globalPosition().toPoint() - this->frameGeometry().topLeft();
#elselastPos = event->globalPos() - this->frameGeometry().topLeft();
#endif}
}// 窗口变化事件
void framelessWidget::resizeEvent(QResizeEvent *event)
{//Resize borderif(border)border->resize(ui->mainWidget->size() + QSize(2, 2));//Resize maskQPainterPath path;
#ifdef Q_OS_WINDOWSpath.addRoundedRect(ui->mainWidget->rect(), cornerRadius - 1, cornerRadius - 1);
#elsepath.addRect(ui->mainWidget->rect());
#endifQRegion mask(path.toFillPolygon().toPolygon());ui->mainWidget->setMask(mask);//Resize all pages
//    for(int i = 0; i < pageList.size(); i++){
//        pageList[i]->resize(ui->mainWidget->width() * 0.4 < pageList[i]->preferWidth ? pageList[i]->preferWidth - 1 : ui->mainWidget->width() * 0.4 - 1, ui->mainWidget->height());
//        pageList[i]->resize(pageList[i]->width() + 1, pageList[i]->height());
//    }
}//点击最大化按钮事件
void framelessWidget::controlWindowScale(){
#ifdef Q_OS_WINDOWSif(!maximized){lastGeometry = this->frameGeometry();//  windowShadow->setEnabled(false);ui->verticalLayout->setContentsMargins(0, 0, 0, 0);border->hide();QString mainStyle = "QWidget#mainWidget{background-color:rgb(251,251,251) border-radius:0px;}";ui->mainWidget->setStyleSheet(mainStyle);this->showMaximized();maximized = true;QPainterPath path;path.addRect(ui->mainWidget->rect());QRegion mask(path.toFillPolygon().toPolygon());ui->mainWidget->setMask(mask);}else{ui->verticalLayout->setContentsMargins(30, 30, 30, 30);this->showNormal();QString mainStyle = "QWidget#mainWidget{background-color:rgb(251,251,251)" + QString::asprintf(";border-radius:%dpx", cornerRadius) + "}";ui->mainWidget->setStyleSheet(mainStyle);QPainterPath path;path.addRoundedRect(ui->mainWidget->rect(), cornerRadius - 1, cornerRadius - 1);QRegion mask(path.toFillPolygon().toPolygon());ui->mainWidget->setMask(mask);border->show();//   windowShadow->setEnabled(true);this->resize(lastGeometry.width(), lastGeometry.height());this->move(lastGeometry.x(), lastGeometry.y());maximized = false;}
#endif
}

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