Thread: Wm_timer

I would like to call DrawPolygon (hwnd, hdc) in ID_TIMER2 but i dont know how.
I get uninitialized local variable 'hdc' error.

Code:

#include <windows.h>
#include <winuser.h>

#define ID_TIMER1    1
#define ID_TIMER2    2


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

void DrawRectangle (HWND) ;
void DrawEllipse (HWND,HDC) ;
void DrawPolygon (HWND hwnd,HDC hdc) ;
int cxClient, cyClient ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("Screensaver") ;
     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         = LoadIcon (NULL, IDI_APPLICATION) ;
     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 ("Beeper1 Timer Demo"),
                          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 ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     HBRUSH      hBrush ;
     static BOOL fFlipFlop = FALSE ;
     HDC         hdc ;
     PAINTSTRUCT ps ;
     RECT        rc ;
     
     
     switch (message)
     {
     case WM_SIZE:
          cxClient = LOWORD (lParam) ;
          cyClient = HIWORD (lParam) ;
          return 0 ;
     
     case WM_CREATE:
          SetTimer (hwnd, ID_TIMER1, 2000, NULL) ;
          SetTimer (hwnd, ID_TIMER2, 1000, NULL) ;
          return 0 ;

     case WM_TIMER :
          switch (wParam)
          {
          case ID_TIMER1:
                  fFlipFlop = !fFlipFlop ;
                    InvalidateRect (hwnd, NULL, FALSE) ;
                   break ;
          case ID_TIMER2:  
                  DrawPolygon (hwnd, hdc);
                  break ;
           }
           return 0 ;

     case WM_PAINT :
          hdc = BeginPaint (hwnd, &ps) ;
          
          GetClientRect (hwnd, &rc) ;
          hBrush = CreateSolidBrush (RGB(0,0,0)) ;
          FillRect (hdc, &rc, hBrush) ;
          DrawPolygon (hwnd, hdc);
          fFlipFlop ? DrawRectangle (hwnd) : DrawEllipse (hwnd,hdc) ;
        
          EndPaint (hwnd, &ps) ;
          DeleteObject (hBrush) ;
          return 0 ;
          
     case WM_DESTROY :
          KillTimer (hwnd, 1) ;
          KillTimer (hwnd, 2) ;
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

void DrawRectangle (HWND hwnd)
{
     HBRUSH hBrush ;
     HDC    hdc ;
     RECT   rect ;
     
     if (cxClient == 0 || cyClient == 0)
          return ;
     
     SetRect (&rect, rand () % cxClient, rand () % cyClient, rand () % cxClient, rand () % cyClient) ;
     
     hBrush = CreateSolidBrush ( RGB (rand () % 256, rand () % 256, rand () % 256)) ;
     hdc = GetDC (hwnd) ;
     
     FillRect (hdc, &rect, hBrush) ;
     ReleaseDC (hwnd, hdc) ;
     DeleteObject (hBrush) ;
}     

void DrawEllipse (HWND hwnd,HDC hdc) 
{
     HBRUSH hbr = CreateSolidBrush (RGB (rand () % 256, rand () % 256, rand () % 256)) ;
     HBRUSH hOld = (HBRUSH) SelectObject (hdc,hbr);
     Ellipse (hdc, rand () % cxClient, rand () % cyClient, rand () % cxClient, rand () % cyClient) ;
     SelectObject (hdc,hOld) ;
     DeleteObject (hbr) ;
}
void DrawPolygon (HWND hwnd, HDC hdc)
{
     static    POINT points[7] = {{20, 50},{180, 50},{180, 20},{230, 70},
                              {180, 120},{180, 90},{20, 90}};
    
     HBRUSH hbr = CreateSolidBrush (RGB (rand () % 256, rand () % 256, rand () % 256)) ;
     HBRUSH hOld = (HBRUSH) SelectObject (hdc,hbr);
     
     Polygon(hdc, points, 7);
     
     SelectObject (hdc,hOld) ;
     DeleteObject (hbr) ;
}