void GetScreenInfo()
{
    QDesktopWidget* desktopWidget = QApplication::desktop();
    //獲取可用桌面大小
    QRect deskRect = desktopWidget->availableGeometry();
    int   m_nActScreenX = deskRect.width();
    int   m_nActScreenY = deskRect.height();
    //獲取設備屏幕大小
    QRect screenRect = desktopWidget->screenGeometry();
 
//    m_nActScreenX = screenRect.width();
//    m_nActScreenY = screenRect.height();


    //獲取系統設置的屏幕個數（屏幕拷貝方式該值為1）
//    int g_nScreenCount = desktopWidget->screenCount();
}

Qt 獲取屏幕信息