Question

How to detect inactive (idle) user in Windows application? I’d like to shutdown application when there hasn’t been any input (keyboard, mouse) from user for certain period of time.

Answer 1

To track a user’s idle time you could hook keyboard and mouse activity. Note, however, that installing a system-wide message hook is a very invasive thing to do and should be avoided if possible, since it will require your hook DLL to be loaded into all processes.

Another solution is to use the GetLastInputInfo API function (if your application is running on Win2000 (and up) machines).
GetLastInputInfo retrieves the time (in milliseconds) of the last input event (when the last detected user activity has been received, be it from keyboard or mouse).

Here’s a simple example. The SecondsIdle function returns a number of second with no user activity (called in an OnTimer event of a TTimer component).

~~~~~~~~~~~~~~~~~~~~~~~~~
function SecondsIdle: DWord;
var
   liInfo: TLastInputInfo;
begin
   liInfo.cbSize := SizeOf(TLastInputInfo) ;
   GetLastInputInfo(liInfo) ;
   Result := (GetTickCount - liInfo.dwTime) DIV 1000;
end;

procedure TForm1.Timer1Timer(Sender: TObject) ;
begin
   Caption := Format('System IDLE last %d seconds', [SecondsIdle]) ;
end;

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