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：