Programmatically prevent Windows screensaver from starting

Question

Is there a recommended way to prevent the Windows screensaver from starting? The closest thing I\'ve found is this article, but what I would really like to do is just tell

Answer 1

You can use SystemParametersInfo to get the SCREENSAVETIMEOUT and then immediately set the timeout back to the same value. Do this periodically on a timer for as long as you want to prevent the screensaver from going on.

This has the effect of resetting the current countdown timer without actually changing the system setting.

You probably also want to call SetThreadExecutionState to affect the power as other answers mention.

Answer 2

From MSDN:

Windows does not start the screen saver if any of the following conditions exist:

• The active application is not a Windows-based application.
• A CBT window is present.
• The active application receives the WM_SYSCOMMAND message with the wParam parameter set to the SC_SCREENSAVE value, but it does not pass the message to the DefWindowProc function.

There's a caveat though:

Windows Vista and later: If password protection is enabled by policy, the screen saver is started regardless of what an application does with the SC_SCREENSAVE notification.

That seems to apply even if you use the SetThreadExecutionState with ES_CONTINUOUS.

So, if it weren't for the caveat, your choices would be:

1. SetThreadExecutionState with ES_CONTINUOUS (as described in other answers).
2. Put up a computer-based training window (which requires hooks).
3. Don't let the WM_SYSCOMMAND with SC_SCREENSAVE be passed onto DefWindowProc. (Assuming you care only when your application is the active application.)
4. Install a dongle that simulates mouse jiggle.

The last option is nice in that it works even with the password protection policy.

Answer 3

In Windows 7+, use the Power Management API's PowerSetRequest() with PowerRequestDisplayRequired

https://msdn.microsoft.com/en-us/library/windows/desktop/dd405534(v=vs.85).aspx

In previous versions of windows, intercept the WM_SYSCOMMAND - SC_SCREENSAVE message as detailed in Eddie Parker's answer.

Answer 4

Just reset the timeout counter with

SystemParametersInfo(SPI_SETSCREENSAVEACTIVE, 1, nil, SPIF_SENDWININICHANGE);

Answer 5

As Adrian McCarthy mentioned from MSDN that :

If password protection is enabled by policy, the screen saver is started regardless of what an application does with the SC_SCREENSAVE notification.

So catch the event from WM_SYSCOMMAND using UINT SC_SCREENSAVE and discarded it by returning 0 or by creating a fake mouse move ("mouse_event(MOUSEEVENTF_MOVE, 0, 1, 0, 0)") will not work properly if the user enabled password-protected screen saver option.

Use SetThreadExecutionState winAPI to tell the operating system that the thread is in use, even if the user is not interacting with the computer. These will prevent to appear screen saver and stop the machine from being suspended automatically.

There are series of flags to specify a new state for the current thread:

• ES_AWAYMODE_REQUIRED (0x00000040) : Enables away mode.
• ES_DISPLAY_REQUIRED (0x00000002) : Forces the display to be on by resetting the display idle timer.
• ES_SYSTEM_REQUIRED (0x00000001) : Forces the system to be in the working state by resetting the system idle timer.
• ES_CONTINUOUS (0x80000000) : Informs the system that the state being set should remain in effect until the next call that uses ES_CONTINUOUS and one of the other state flags are cleared.

As it's a winAPI, you can call this directly in win32 or mfc application

//To stop/start screen saver and monitor power off event
void SetKeepScreenOn(BOOL isKeepScreenOn)
{
   if (isKeepScreenOn == TRUE)
   {
       SetThreadExecutionState(ES_CONTINUOUS | ES_SYSTEM_REQUIRED | ES_DISPLAY_REQUIRED /*| ES_AWAYMODE_REQUIRED*/);        
   }
   else
   {
       SetThreadExecutionState(ES_CONTINUOUS);      
   }
}

If someone wants to use this in C#, must have to PInvoke this :

[DllImport("kernel32.dll", CharSet = CharSet.Auto,SetLastError = true)]
static extern EXECUTION_STATE SetThreadExecutionState(EXECUTION_STATE esFlags);

User-Defined Types:

[FlagsAttribute]
public enum EXECUTION_STATE :uint
{
   ES_AWAYMODE_REQUIRED = 0x00000040,
   ES_CONTINUOUS = 0x80000000,
   ES_DISPLAY_REQUIRED = 0x00000002,
   ES_SYSTEM_REQUIRED = 0x00000001
}

Here below is the calling procedure:

void SetKeepScreenOn(bool isKeepScreenOn)
{
    if (isKeepScreenOn == true)
    {
         //You can combine several flags and specify multiple behaviors with a single call
         SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS | EXECUTION_STATE.ES_SYSTEM_REQUIRED | EXECUTION_STATE.ES_DISPLAY_REQUIRED /*| EXECUTION_STATE.ES_AWAYMODE_REQUIRED*/);        
    }
    else
    {
         //To reset or allow those event again you have to call this API with only ES_CONTINUOUS
         SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS);      
    }
 }

According to MSDN this API is safe also to use.

The system maintains a count of applications that have called SetThreadExecutionState. The system tracks each thread that calls SetThreadExecutionState and adjusts the counter accordingly. If this counter reaches zero and there has not been any user input, the system enters sleep.

If the Application crashed before resetting flag, the System will adjust and will reset automatically.

Answer 6

I use Mouse Jiggler to reset the idle state. This gets around a Group Policy that tends to start my screensaver (and lock the machine) at inopportune times: when I'm reading a long document, studying a complex chunk of code, or talking/listening/not-constantly-typing during a meeting.

As it can be slightly annoying to have the mouse jump 1px diagonally every second, I intend to use AutoHotKey to write a script that does basically the same thing, but only after a configured keyboard/mouse idle timeout, and maybe use the Shift key (or Scroll Lock) instead of a mouse move.