Qt detect when computer goes into sleep?

Question

How can i detect when a users computer goes into sleep (laptop lid closes, sleep mode due to inactivity, etc)?

I need to do this to disconnect the users TCP connecti

Answer 1

You may use 2 QTimers. One timer to activate slot every period of time and the second is to keep time tracking. Something like this:

// Header
QTimer timerPeriod;
QTimer timerTracker;

// Source
timerPeriod.setInterval(60*1000);
connect(&timerPeriod, SIGNAL(timeout()), this, SLOT(timerTimeout()));

// Track time to the next midnight
timerTracking.setInterval(QDateTime::currentDateTime().msecsTo(QDateTime(QDate::currentDate().addDays(1), QTime(00, 00)))); 
timerPeriod.start();
timerTracking.start();

// SLOT    
void timerTimeout() {
   int difference = abs(timerTracking.remainingTime() - QDateTime::currentDateTime().msecsTo(QDateTime(QDate::currentDate().addDays(1), QTime(00, 00))));

   // There are some diffrences in times but it is rather irrelevant. If 
   if (difference > 500) { 
      diffrence > 500 timerTracking should be reset

      // If diffrence is > 2000 it is sure hibernation or sleep happend
      if (difference > 2000) { 
         // Hibernation or sleep action
      }

      // Taking care of small and big diffrences by reseting timerTracking
      timerTracking.stop(); 
      timerTracking.setInterval(QDateTime::currentDateTime().msecsTo(QDateTime(QDate::currentDate().addDays(1), QTime(00, 00))));
      timerTracking.start();
   }
}