Cannot send keys to screensaver in windows 10

Question

How can I send keys to a screensaver in Windows 10. I have tried to install my own screensaver and have disabled logon screen so I only need a keypress to show my desktop. I Guess a part of the problem is use of different desktop, but even With the code shown in the link bellow I cannot figure out how to send a key Message to the screensaver. Any suggestions?

http://www.delphipraxis.net/1059352-post7.html

Answer 1

This is an XY Problem. You are asking how to send keys to a screensaver to deactivate it, so it does not interfere with simulated mouse clicks you want to send to another app. That is the wrong question to ask. You should be asking how to disable the screensaver from running in the first place while your app is busy interacting with the other app.

You say you have disabled the screensaver password. In which case, you can have your app handle the WM_SYSCOMMAND message. If the message's wParam value has the SC_SCREENSAVE flag enabled, discard the message without passing it to the default message handler. Then the screensaver will not run. This only works if your app is in the foreground at the time (SC_SCREENSAVE is only sent to the foreground window), and only if the screensaver password is disabled, though:

If password protection is enabled by policy, the screen saver is started regardless of what an application does with the SC_SCREENSAVE notification—even if fails to pass it to DefWindowProc.

If you need to handle the message while your app is not in the foreground, you can use a global message hook via SetWindowsHookEx() to change WM_SYSCOMMAND/SC_SCREENSAVE messages into WM_NULL when being sent to any HWND in the system.

An alternative approach (only if the screensaver is not already running) is to use SystemParametersInfo() to set SPI_SETSCREENSAVEACTIVE to TRUE to make the system think that a screensaver is already running so it wont start another one (you can use SPI_GETSCREENSAVERRUNNING to check if one is running). This is an old-school way to avoid a screensaver from starting, however on Vista+ onwards with added security policies and such, this probably does not work as well as it once did.

Another alternative is to disable the screensaver in the Registry while your app is busy*. Set the HKEY_CURRENT_USER\ControlPanel\Desktop\ScreenSaveActive value to 0 (just make sure to restore it before your app exits).

_{*This technique is even used by Windows itself (Vista+) if the user dismisses the screensaver immediately after it starts. Windows assumes the user is annoyed with the screensaver, so the screensaver gets disabled, and is then re-enabled a few minutes later.}

Answer 2

I had given up on this but i stumbled over the following code that Works

 function KillScreenSaverFunc(Handle: hwnd; Temp: LongInt): Boolean; stdcall;
 begin
   PostMessage(Handle, WM_CLOSE, 0, 0);
   KillScreenSaverFunc := TRUE;
 end;

procedure KillScreenSaver;
var
  myHDESK:hdesk;
begin
   myhdesk := OpenDesktop(Pchar('Screen-saver'), 0, FALSE,      
   DESKTOP_READOBJECTS or DESKTOP_WRITEOBJECTS);
   if myhdesk<>0 then begin
    EnumDesktopWindows(myhdesk, @KillScreenSaverFunc, 0);
          CloseDesktop(myhdesk);
 end;
end;