#include <windows.h>
 
#define ERROR_NUMBER_ARGS -1
#define ERROR_CREATING_SEMAPHORE -2
 
#define SEMAPHORE_NAME "DISABLE_SCREENSAVER_SEMAPHORE"
 
BOOL show_last_error()
{
    char pcError[255];
    DWORD dw=FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM,NULL,
                           GetLastError(),GetSystemDefaultLangID(), 
                           pcError,sizeof(pcError)-1,NULL);
 
    if (dw==0)
        return FALSE;// FormatMessage failed
    else
    {
        MessageBox(NULL,pcError,"Error",MB_OK|MB_ICONERROR);
        return TRUE;
    }
}
 
void show_usage()
{
    MessageBox(NULL,"The use of this software is the following:\r\n
               DisableScreenSaver.exe /ApplicationName\r\n
               where \"ApplicationName\" is the full path of the application you want to launch",
               "Information",MB_OK|MB_ICONINFORMATION);
}
 
// disable screensaver
void disable_screensaver()
{
    BOOL b_res;
    b_res=SystemParametersInfo(SPI_SETSCREENSAVEACTIVE, FALSE, NULL, 0);
    if (!b_res)
        show_last_error();
    b_res=SystemParametersInfo(SPI_SETLOWPOWERACTIVE,0,NULL,0);
    if (!b_res)
        show_last_error();
    b_res=SystemParametersInfo(SPI_SETPOWEROFFACTIVE,0,NULL,0);
    if (!b_res)
        show_last_error();
}
 
void launch_and_wait_process(char* pc_fullpath)
{
    STARTUPINFO si;
    PROCESS_INFORMATION pi;
 
    ZeroMemory( &si, sizeof(si) );
    si.cb = sizeof(si);
    ZeroMemory( &pi, sizeof(pi) );
 
    // create directory path
    char pc_application_directory[MAX_PATH];
    char* ptr_application_directory;
 
    int len=(int)strlen(pc_fullpath);
    if (len>0)
    {
        // remove / if any
        if (pc_fullpath[0]=='/')
        {
            pc_fullpath=&pc_fullpath[1];
            len--;
        }
    }
    if (len>0)
    {
        // remove " at the begining of pc_fullpath if any
        if (pc_fullpath[0]=='"')
        {
            pc_fullpath=&pc_fullpath[1];
            len--;
        }
    }
    if (len>0)
    {
        // remove " at the end of pc_fullpath if any
        if (pc_fullpath[len-1]=='"')
            pc_fullpath[len-1]=0;
    }
 
    strncpy(pc_application_directory,pc_fullpath,MAX_PATH);
    char* ptr=strrchr(pc_application_directory,'\\');
    if (ptr)
    {
        *ptr=0;
        ptr_application_directory=pc_application_directory;
    }
    else
        ptr_application_directory=NULL;
 
    // Start the child process. 
    if( !CreateProcess( NULL,   // No module name (use command line). 
        pc_fullpath,            // Command line. 
        NULL,                   // Process handle not inheritable. 
        NULL,                   // Thread handle not inheritable. 
        FALSE,                  // Set handle inheritance to FALSE. 
        0,                      // No creation flags. 
        NULL,                   // Use parent's environment block. 
        ptr_application_directory,// Use parent's starting directory. 
        &si,                    // Pointer to STARTUPINFO structure.
        &pi )                   // Pointer to PROCESS_INFORMATION structure.
    ) 
    {
        show_last_error();
        // Close process and thread handles. 
        CloseHandle( pi.hProcess );
        CloseHandle( pi.hThread );
        return;
    }
 
    // Wait until child process exits.
    // WaitForSingleObject( pi.hProcess, INFINITE );
 
    // Wait until child process exits and assume 
    // screen saver is disable every minute (min screen saver enabling)
    DWORD dwRes=WAIT_TIMEOUT;
    while (dwRes==WAIT_TIMEOUT)
    {
        dwRes=WaitForSingleObject( pi.hProcess, 59000 );
        disable_screensaver();
    }
 
    // Close process and thread handles. 
    CloseHandle( pi.hProcess );
    CloseHandle( pi.hThread );
}
 
int __stdcall WinMain(HINSTANCE hInstance,
            HINSTANCE hPrevInstance,
            LPSTR lpCmdLine,
            int nCmdShow)
{
    UNREFERENCED_PARAMETER(hInstance);
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(nCmdShow);
    BOOL b_res;
    HANDLE hnd_semaphore;
    DWORD dw_res_wait;
 
    // check if there's arguments
    if (strlen(lpCmdLine)==0)
    {
        show_usage();
        return ERROR_NUMBER_ARGS;
    }
    //try to open semaphore
    hnd_semaphore=OpenSemaphore(EVENT_ALL_ACCESS,FALSE,SEMAPHORE_NAME);
    
    // if not named semaphore is not existing, create semaphore and disable screensaver
    if (!hnd_semaphore)
    {
        // create semaphore
        hnd_semaphore=CreateSemaphore(
                                        NULL,// security attr
                                        0,// initial count
                                        0x7FFF,// max count
                                        SEMAPHORE_NAME
                                     );
        if (!hnd_semaphore)
        {
            show_last_error();
            return ERROR_CREATING_SEMAPHORE;
        }
        // disable screensaver
        disable_screensaver();
    }
    else
    {
        b_res=ReleaseSemaphore(hnd_semaphore,1,NULL);
        if (!b_res)
            show_last_error();
    }
    // launch process and wait for it's end
    launch_and_wait_process(lpCmdLine);
 
    // WaitForSingleObject decrease the count of semaphores
    // WaitForSingleObject time out --> there's no more other instance of disable_screensaver --> enable screensaver
    dw_res_wait=WaitForSingleObject(hnd_semaphore,0);
    if (dw_res_wait==WAIT_TIMEOUT)
    {
        // enable screensaver
        b_res=SystemParametersInfo(SPI_SETSCREENSAVEACTIVE, TRUE, NULL, 0);
        if (!b_res)
            show_last_error();
        b_res=SystemParametersInfo(SPI_SETLOWPOWERACTIVE,1,NULL,0);
        if (!b_res)
            show_last_error();
        b_res=SystemParametersInfo(SPI_SETPOWEROFFACTIVE,1,NULL,0);
        if (!b_res)
            show_last_error();
    }
 
    // close semaphore handle
    CloseHandle(hnd_semaphore);
 
    return ERROR_SUCCESS;
}