Preventing Windows Screen-Saver Activation

Originally published on: Tue, 20 Oct 2009 00:54:54 +0000

Please note! If you're having difficulties compiling the C source code presented below, please see my post: Compiling C from the Command Line with Pelles C

Some time ago, I wanted to see if the simulated mouse moves generated via calls to the WIN32 API mouse_event function would prevent the screen-saver from triggering.

In the current version of XP ( and some older versions of Windows ) these events do indeed keep the screen-saver from activating.

Please refer to the source below.

busy_mouse.c

// Generate mouse events to prevent the screen-saver from
// activating.
//
// License: MIT / X11
// Copyright (c) 2009 by James K. Lawless
// jimbo@radiks.net http://www.radiks.net/~jimbo
// http://www.mailsend-online.com
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the &amp;quot;Software&amp;quot;), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED &amp;quot;AS IS&amp;quot;, WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.

// check the state of the Scroll Lock or Caps Lock keys. Return a
// 1 if the requested key is active/on.

#include &amp;lt;windows.h&amp;gt;
#include &amp;lt;stdio.h&amp;gt;
#include &amp;lt;string.h&amp;gt;

#pragma comment(lib,&amp;quot;user32.lib&amp;quot;)

void process_messages(void);

int main(int argc,char **argv) {
   int i;
   printf(&amp;quot;Busy Mouse v1.0 by Jim Lawlessn&amp;quot;);
   printf(&amp;quot;If CAPS LOCK is on, the mouse cursor will move around to prevent any screen-savers from activating.n&amp;quot;);
   for(;;) {
      while(GetKeyState(VK_CAPITAL)&amp;amp;1) {
         for(i=0;i&amp;lt;50;i+=2) {
            mouse_event( MOUSEEVENTF_MOVE,2,0,0,0 );
            process_messages();
         }
         Sleep(200);

         for(i=0;i&amp;lt;50;i+=2) {
            mouse_event( MOUSEEVENTF_MOVE,0,2,0,0 );
            process_messages();
         }
         Sleep(200);

         for(i=0;i&amp;lt;50;i+=2) {
            mouse_event( MOUSEEVENTF_MOVE,-2,0,0,0 );
            process_messages();
         }
         Sleep(200);

         for(i=0;i&amp;lt;50;i+=2) {
            mouse_event( MOUSEEVENTF_MOVE,0,-2,0,0 );
            process_messages();
         }
         Sleep(200);
      }
   }
   processMessages();
}

void process_messages(void) {
MSG m;
while( PeekMessage(&amp;amp;m,0,0,0,PM_REMOVE)) {
    TranslateMessage(&amp;amp;m);
DispatchMessage(&amp;amp;m);
}
}

When you run busy_mouse.exe the program will loop indefinitely. The program checks the CAPS LOCK state. If CAPS LOCK is enabled, it will then move the mouse in a rectangular pattern via mouse_event().

When CAPS LOCK is off, the simulated mouse events halt.

I've used this to keep the screen visible so that I can watch for emails or processes that run long while I'm away from the mouse and keyboard.

The source and executable file for busy_mouse can be downloaded in a single archive at: http://www.mailsend-online.com/wp/busy_mouse.zip

Unless otherwise noted, all code and text entries are Copyright Š2009 by James K. Lawless

Views expressed in this blog are those of the author and do not necessary reflect those of the author's employer. Views expressed in the comments are those of the responding individual.

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