第五章 绘图基础（ALTWIND）

线上箭头表示画线的方向。WINDING模式和ALTERNATE模式都会填充三个封闭的L型区域，号码从1到3。两个更小的内部区域，号码为4和5，在ALTERNATE模式下不被填充。但是在WINDING模式下，号码5的区域会被填充，这是因为区域的内部到达图形的外部必须穿过两条相同方向的线。号码为4的区域不会被填充，因为射线必须穿越两条边框线，但是这两条边框线的绘制方向相反。

 /*-------------------------------------------
 ALTWIND.C -- Alternate and Winding Fill Modes
              (c) Charles Petzold, 1998
 -------------------------------------------*/

 #include <Windows.h>

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

 int WINAPI WinMain( __in HINSTANCE hInstance
                     , __in_opt HINSTANCE hPrevInstance
                     , __in LPSTR lpCmdLine
                     , __in int nShowCmd )
 {
     static TCHAR szAppName[] = TEXT("AltWind");
     HWND hwnd;
     MSG msg;
     WNDCLASS wndclass;

     wndclass.style = CS_HREDRAW | CS_VREDRAW;
     wndclass.lpfnWndProc = WndProc;
     wndclass.cbClsExtra = ;
     wndclass.cbWndExtra = ;
     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 ;
     }

     hwnd= CreateWindow(szAppName, TEXT("Alternate and Winding Fill Modes")
         , WS_OVERLAPPEDWINDOW
         , CW_USEDEFAULT, CW_USEDEFAULT
         , CW_USEDEFAULT, CW_USEDEFAULT
         , NULL, NULL, hInstance, NULL);

     ShowWindow(hwnd, nShowCmd);
     UpdateWindow(hwnd);

     while (GetMessage(&msg, NULL, , ))
     {
         TranslateMessage(&msg);
         DispatchMessage(&msg);
     }

     return msg.wParam;
 }

 LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
     static POINT aptFigure[] = {,
                                 , ,
                                 , ,
                                 , ,
                                 , ,
                                 , ,
                                 , ,
                                 , ,
                                 , ,
                                 , , };
     static int cxClient, cyClient;
     HDC hdc;
     int i;
     PAINTSTRUCT ps;
     POINT apt[];

     switch (message)
     {
     case WM_SIZE:
         cxClient = LOWORD(lParam);
         cyClient = HIWORD(lParam);
         return ;

     case WM_PAINT:
         hdc = BeginPaint(hwnd, &ps);
         SelectObject(hdc, GetStockObject(GRAY_BRUSH));

         for (i = ; i !=; ++i)
         {
             apt[i].x = cxClient * aptFigure[i].x / ;
             apt[i].y = cyClient * aptFigure[i].y / ;
         }
         SetPolyFillMode(hdc, ALTERNATE);
         Polygon(hdc, apt, );

         for (i = ; i != ; ++i)
         {
             apt[i].x += cxClient / ;
         }
         SetPolyFillMode(hdc, WINDING);
         Polygon(hdc, apt, );

         EndPaint(hwnd, &ps);
         return ;

     case WM_DESTROY:
         PostQuitMessage();
         return ;
     }

     return DefWindowProc(hwnd, message, wParam, lParam);
 }

ALTWIND.C

图形的坐标（按一个100*100单位的区域设定）存储在aptFigure数组中。这些坐标会根据客户去的宽度和高度按比例缩放。程序显示两个图形，一个使用ALTERNATE填充模式，另一个使用WINDING填充模式。结果如图：