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 connection. Basically we got a simple chat application where we want to take the user off-line.

Answer 1

There is no Qt way to detect when computer goes to sleep or hibernation. But there are some platform dependent ways to do it.

On Windows you can listen for the WM_POWERBROADCAST message in your WindowProc handler:

LRESULT WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
  if (WM_POWERBROADCAST == message && PBT_APMSUSPEND == wParam) {
    // Going to sleep
  }
}

On linux you can put the following shell script in /etc/pm/sleep.d which executes a program with arguments. You can start a program and notify your main application in some way:

#!/bin/bash
case $1 in
suspend)
    #suspending to RAM
    /Path/to/Program/executable Sleeping
    ;;
resume)
    #resume from suspend
    sleep 3
    /Path/to/Program/executable Woken
    ;;
esac

For OS X you can see this.