QT4和QT5中的截圖

//this->m_pixMap = QPixmap::grabWindow(QApplication::desktop()->winId(), 0, 0, -1, -1);
//this->m_pixMap = QWidget::grab(QRect( QPoint( 0, 0 ), QSize( -1, -1 ) ));
QScreen* screen = QGuiApplication::primaryScreen();
this->m_pixMap = screen->grabWindow(QApplication::desktop()->winId(), 0, 0, -1, -1);

使用QWidget::grab再QT5中會有警告
this function is deprecated, use QScreen::grabWindow() instead. Defaulting to primary screen.

使用第二種只截取當前App的界面，非桌面全屏
使用第三種沒有警告，且截取的是桌面全屏

參考 Qt5和Qt4的簡單截屏;