#include <windows.h>
#include <math.h>

#define ID_TIMER    1
#define TWOPI      (2 * 3.14159)

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT ("Clock") ;
    HWND        hwnd;
    MSG          msg;
    WNDCLASS    wndclass ;
    
    wndclass.style        = CS_HREDRAW | CS_VREDRAW ;
    wndclass.lpfnWndProc  = WndProc ;
    wndclass.cbClsExtra    = 0 ;
    wndclass.cbWndExtra    = 0 ;
    wndclass.hInstance    = hInstance ;
    wndclass.hIcon        = NULL ;
    wndclass.hCursor      = LoadCursor (NULL, IDC_ARROW) ;
    wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
    wndclass.lpszMenuName  = NULL ;
    wndclass.lpszClassName = szAppName ;
    
    if (!RegisterClass (&wndclass))
    {
          MessageBox (NULL, TEXT ("Program requires Windows NT!"), 
                      szAppName, MB_ICONERROR) ;
          return 0 ;
    }

    hwnd = CreateWindow (szAppName, TEXT ("Analog Clock"),
                          WS_OVERLAPPEDWINDOW,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;
    
    ShowWindow (hwnd, iCmdShow) ;
    UpdateWindow (hwnd) ;
    
    while (GetMessage (&msg, NULL, 0, 0))
    {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
    }
    return msg.wParam ;
}

void SetIsotropic (HDC hdc, int cxClient, int cyClient)
{
    SetMapMode (hdc, MM_ISOTROPIC) ;
    SetWindowExtEx (hdc, 1000, 1000, NULL) ;
    SetViewportExtEx (hdc, cxClient / 2, -cyClient / 2, NULL) ;
    SetViewportOrgEx (hdc, cxClient / 2,  cyClient / 2, NULL) ;
}

void RotatePoint (POINT pt[], int iNum, int iAngle)
{
    int  i ;
    POINT ptTemp ;
    
    for (i = 0 ; i < iNum ; i++)
    {
          ptTemp.x = (int) (pt[i].x * cos (TWOPI * iAngle / 360) +
              pt[i].y * sin (TWOPI * iAngle / 360)) ;
          
          ptTemp.y = (int) (pt[i].y * cos (TWOPI * iAngle / 360) -
              pt[i].x * sin (TWOPI * iAngle / 360)) ;
          
          pt[i] = ptTemp ;
    }
}

void DrawClock (HDC hdc)
{
    int  iAngle ;
    POINT pt[3] ;

    for (iAngle = 0 ; iAngle < 360 ; iAngle += 6)
    {
          pt[0].x =  0 ;
          pt[0].y = 900 ;
          
          RotatePoint (pt, 1, iAngle) ;
          
          pt[2].x = pt[2].y = iAngle % 5 ? 33 : 100 ;
          
          pt[0].x -= pt[2].x / 2 ;
          pt[0].y -= pt[2].y / 2 ;
          
          pt[1].x  = pt[0].x + pt[2].x ;
          pt[1].y  = pt[0].y + pt[2].y ;
          
          SelectObject (hdc, GetStockObject (BLACK_BRUSH)) ;
          
          Ellipse (hdc, pt[0].x, pt[0].y, pt[1].x, pt[1].y) ;
    }
}

void DrawHands (HDC hdc, SYSTEMTIME * pst, BOOL fChange)
{
    static POINT pt[3][5] = { 0, -150, 100, 0, 0, 600, -100, 0, 0, -150,
                              0, -200,  50, 0, 0, 800,  -50, 0, 0, -200,
                              0,    0,  0, 0, 0,  0,    0, 0, 0,  800 } ;
    int          i, iAngle[3] ;
    POINT        ptTemp[3][5] ;
    
    iAngle[0] = (pst->wHour * 30) % 360 + pst->wMinute / 2 ;
    iAngle[1] =  pst->wMinute  *  6 ;
    iAngle[2] =  pst->wSecond  *  6 ;
    
    memcpy (ptTemp, pt, sizeof (pt)) ;
    
    for (i = fChange ? 0 : 2 ; i < 3 ; i++)
    {
          RotatePoint (ptTemp[i], 5, iAngle[i]) ;
          
          Polyline (hdc, ptTemp[i], 5) ;
    }
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static int        cxClient, cyClient ;
    static SYSTEMTIME stPrevious ;
    BOOL              fChange ;
    HDC              hdc ;
    PAINTSTRUCT      ps ;
    SYSTEMTIME        st ;
          
    switch (message)
    {
    case WM_CREATE :
          SetTimer (hwnd, ID_TIMER, 1000, NULL) ;
          GetLocalTime (&st) ;
          stPrevious = st ;
          return 0 ;
          
    case WM_SIZE :
          cxClient = LOWORD (lParam) ;
          cyClient = HIWORD (lParam) ;
          return 0 ;
          
    case WM_TIMER :
          GetLocalTime (&st) ;
                    
          fChange = st.wHour  != stPrevious.wHour ||
                    st.wMinute != stPrevious.wMinute ;
          
          hdc = GetDC (hwnd) ;
          
          SetIsotropic (hdc, cxClient, cyClient) ;
          
          SelectObject (hdc, GetStockObject (WHITE_PEN)) ;
          DrawHands (hdc, &stPrevious, fChange) ;
          
          SelectObject (hdc, GetStockObject (BLACK_PEN)) ;
          DrawHands (hdc, &st, TRUE) ;
          
          ReleaseDC (hwnd, hdc) ;
          
          stPrevious = st ;
          return 0 ;
          
    case WM_PAINT :
          hdc = BeginPaint (hwnd, &ps) ;
          
          SetIsotropic (hdc, cxClient, cyClient) ;

          DrawClock    (hdc) ;
          DrawHands    (hdc, &stPrevious, TRUE) ;
          
          EndPaint (hwnd, &ps) ;
          return 0 ;
          
    case WM_DESTROY :
          KillTimer (hwnd, ID_TIMER) ;
          PostQuitMessage (0) ;
          return 0 ;
    }
    return DefWindowProc (hwnd, message, wParam, lParam) ;
}