Author: Lou Adler

Anyone have suggestions on how to implement an inactivity timer? My application has 
passwords for various functions, and I need to be able to automatically logout a 
user if they've been inactive for 10 minutes, etc.. I suppose I'd tie into the 
messaging queue, looking at keyboard and mouse events. The implementation should 
cover activity related to any form in my application, but not any activity outside 
the application.

Answer:

In your main form, add the integer variables "ShutdownCounter" and "ShutDownDelay". 
Add a TApplicationEvents and a TTimer control. Set the timer interval to, say, 5000 
mSecs. In the form's OnCreate event handler, add:

1   { ... }
2       {Set up the automatic log off routine. Get the users auto logoff time, 
3   		which defaults to 20 minutes. 0 is never autologoff}
4   shutDownDelay := UserIni.ReadInteger('Settings', 'Auto Shutdown Delay', 20);
5   shutDownDelay := shutDownDelay * 60;
6   ShutdownCounter := 0;
7   if shutDownDelay > 0 then
8     timShutDown.Enabled := true;
9       {Enable the timer if you want to use a timeout for this user}

This format allows you to add different logoff times for different users, or 
completely disable autologoff - I do this on my development system.

In the TApplicationEvents OnMessage event handler, add code to check for 
keypresses, or left mouse button clicks (or any other message you want to use to 
keep the app running). Whenever any of these messages are received by the 
application, reset the ShutDownCounter to zero.
10  
11  procedure TfrmAutoProMain.ApplicationEvents1Message(var Msg: tagMSG;
12    var Handled: Boolean);
13  begin
14    case Msg.message of
15      WM_KEYDOWN, WM_LBUTTONDOWN:
16        ShutdownCounter := 0;
17    end;
18  end;


In the TTimer OnTimer event handler, add code to compare the current value of 
ShutDownCounter against the ShutDownDelay for this user. If the counter is larger 
than the delay, then we need to exit the application. In my apps, I actually show 
another window with a 30 second decrementing progress bar which gives the user 
notification that the app is about to shutdown, and gives him a chance to keep the 
app alive - that's the references to dlgAutoLogOff .
19  
20  procedure TfrmAutoProMain.timShutDownTimer(Sender: TObject);
21  begin
22    Inc(ShutdownCounter, 5);
23      {Increase counter by 5 seconds (if TTimer interval was 5000)}
24    if ShutdownCounter >= shutDownDelay then
25    begin
26      timShutDown.Enabled := false;
27      {The next block handles a "last chance" warning dialog to allow the user 
28  		to stay alive}
29      dlgAutoLogOff := TdlgAutoLogOff.Create(self);
30      try
31        dlgAutoLogOff.Show;
32        repeat
33          Application.ProcessMessages;
34        until
35          (dlgAutoLogOff.ModalResult = mrOK) or (dlgAutoLogOff.ModalResult = mrAbort);
36        if dlgAutoLogOff.ModalResult = mrOK then
37        begin
38          ShutdownCounter := 0;
39          timShutDown.Enabled := true;
40        end
41        else
42          Application.Terminate;
43      finally
44        dlgAutoLogOff.Free;
45      end;
46    end;
47  end;