Using Regions in Windows

#include <windows.h>

LRESULT CALLBACK WndProc(
    HWND   hWnd,
    UINT   msg,
    WPARAM wParam,
    LPARAM lParam ) {

  switch( msg ) {
    case WM_PAINT: {
      PAINTSTRUCT ps;
      HDC hDC = BeginPaint( hWnd, &ps );
      TextOut(hDC, 10, 10, "ADP GmbH", 8 );
      EndPaint( hWnd, &ps );
    }
    break;

    case WM_DESTROY:
      PostQuitMessage(0);
    break;

    default:
      return DefWindowProc( hWnd, msg, wParam, lParam);
  } 
  return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 
                   LPSTR lpCmdLine, int nCmdShow) {

  WNDCLASSEX wce;

  wce.cbSize        = sizeof(wce);
  wce.style         = CS_VREDRAW | CS_HREDRAW; 
  wce.lpfnWndProc   = (WNDPROC) WndProc; 
  wce.cbClsExtra    = 0; 
  wce.cbWndExtra    = 0; 
  wce.hInstance     = hInstance; 
  wce.hIcon         = LoadIcon((HINSTANCE) NULL, IDI_APPLICATION); 
  wce.hCursor       = LoadCursor((HINSTANCE) NULL, IDC_ARROW); 
  wce.hbrBackground = (HBRUSH) GetStockObject(WHITE_BRUSH); 
  wce.lpszMenuName  = 0;
  wce.lpszClassName = "ADPWinClass",
  wce.hIconSm       = 0;
 
  if (!RegisterClassEx(&wce)) return 0; 
  
  HWND hWnd = CreateWindowEx(
    0,          // Ex Styles
    "ADPWinClass",
    "ADP GmbH",
     WS_OVERLAPPEDWINDOW,
     400,  // x
     400,  // y
     200,  // Height
     200,  // Width
     NULL,           // Parent Window
     NULL,           // Menu, or windows id if child
     hInstance,      // 
     NULL            // Pointer to window specific data
  );

  ShowWindow( hWnd, nCmdShow );

  POINT points[] = { {   0,  50},
                     {   5, 100},
                     {  90, 150},
                     { 180, 180},
                     {   0,   0}
                   };

  HRGN region = CreatePolygonRgn(points,sizeof(points)/sizeof(POINT),WINDING);
  SetWindowRgn(hWnd,region,true);

  MSG msg;
  int r;
  while ((r = GetMessage(&msg, NULL, 0, 0 )) != 0) { 
    if (r == -1) {
      ;  // Error!
    }
    else {
      TranslateMessage(&msg); 
      DispatchMessage(&msg); 
    }
  } 

  // The application's return value, 'nuff said
  return msg.wParam;
}