GDI 线段绘制示例程序

 #include <windows.h>
 #include <strsafe.h>
 #include <stack>

 typedef struct tagLINE {
     POINT ptStart;
     POINT ptEnd;
 }LINE;

 LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
     HDC hdc;
     PAINTSTRUCT ps;
     TCHAR szBuffer[];
     size_t nLength;
     static int cxClient, cyClient;
     static BOOL fDrawing;
     static LINE arrLine[];
     static int length;
     static LINE line;
     int i;

     switch (message)
     {
     case WM_CREATE:
         length = ;
         fDrawing = FALSE;
         return ;

     case WM_LBUTTONUP:

         if (fDrawing) {
             line.ptEnd.x = LOWORD(lParam);
             line.ptEnd.y = HIWORD(lParam);
             arrLine[length] = line;
             length++;
         }
         else {
             line.ptStart.x = LOWORD(lParam);
             line.ptStart.y = HIWORD(lParam);
         }

         fDrawing = !fDrawing;

         InvalidateRect(hwnd, NULL, TRUE);

         return ;

     case WM_SIZE:
         hdc = GetDC(hwnd);

         cxClient = LOWORD(lParam);
         cyClient = HIWORD(lParam);

         ReleaseDC(hwnd, hdc);
         return ;

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

         for (i = ; i < length; i++) {
             MoveToEx(hdc, arrLine[i].ptStart.x, arrLine[i].ptStart.y, NULL);
             LineTo(hdc, arrLine[i].ptEnd.x, arrLine[i].ptEnd.y);
         }

         StringCchPrintf(szBuffer, sizeof(szBuffer) / sizeof(TCHAR), TEXT("Size: %d x %d"), cxClient, cyClient);
         StringCchLength(szBuffer, sizeof(szBuffer) / sizeof(TCHAR), &nLength);

         SetTextAlign(hdc, TA_TOP | TA_RIGHT);
         TextOut(hdc, cxClient, , szBuffer, nLength);

         EndPaint(hwnd, &ps);
         return ;

     case WM_DESTROY:
         PostQuitMessage();
         return ;
     }

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

 int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdLine)
 {
     LPCTSTR lpszClassName = TEXT("Demo");
     LPCTSTR lpszWindowName = TEXT("Demo Window");

     WNDCLASS wndclass;
     wndclass.cbClsExtra = ;
     wndclass.cbWndExtra = ;
     wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
     wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
     wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
     wndclass.hInstance = hInstance;
     wndclass.lpfnWndProc = WndProc;
     wndclass.lpszClassName = lpszClassName;
     wndclass.lpszMenuName = NULL;
     wndclass.style = CS_HREDRAW | CS_VREDRAW;

     if (!RegisterClass(&wndclass)) {
         MessageBox(NULL, TEXT("This program requires Windows NT!"), TEXT("Error"), MB_ICONERROR);
         return ;
     }

     HWND hwnd = CreateWindow(
         lpszClassName,
         lpszWindowName,
         WS_OVERLAPPEDWINDOW,
         CW_USEDEFAULT,
         CW_USEDEFAULT,
         CW_USEDEFAULT,
         CW_USEDEFAULT,
         NULL,
         NULL,
         hInstance,
         NULL
     );

     ShowWindow(hwnd, nCmdLine);
     UpdateWindow(hwnd);

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

     return msg.wParam;
 }