//Win32 Application: #include<windows.h> #include<math.h> #include<stdlib.h> LRESULT CALLBACK WinProc(HWND,UINT,WPARAM,LPARAM); int cxClient,cyClient; HPEN hpen; #define TWO_PI (2*3.1415926) WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpcmdLine,int nShowCmd) {     HWND hwnd;     MSG msg;     WNDCLASS wc;     TCHAR szAppname[] = TEXT("随机圆");     HBRUSH hbrush;     LOGPEN logpen;     PAINTSTRUCT ps;     HDC hdc;     double radius,i;     POINT pt;     pt.x = 1;     pt.y =2;     wc.cbClsExtra = 0;     wc.cbWndExtra = 0;     wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);     wc.hCursor = LoadCursor(NULL,IDC_ARROW);     wc.hIcon = LoadIcon(NULL,IDI_APPLICATION);     wc.hInstance = hInstance;     wc.lpfnWndProc = WinProc;     wc.lpszClassName = szAppname;     wc.lpszMenuName = NULL;     wc.style = CS_HREDRAW|CS_VREDRAW;     if(!RegisterClass(&wc))     {        MessageBox(NULL,TEXT("警告框"),TEXT("窗口类注册失败!"),MB_ICONERROR);        return 0;     }     hwnd = CreateWindow(szAppname,szAppname,WS_OVERLAPPEDWINDOW,                         CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,                         NULL,NULL,hInstance,NULL);     ShowWindow(hwnd,nShowCmd);     UpdateWindow(hwnd);     while(true)     {          if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))         {         if(msg.message==WM_QUIT) break;                  TranslateMessage(&msg);             DispatchMessage(&msg);         }         else         {                  hdc = GetDC(hwnd);                  SetBkMode(hdc,OPAQUE);  //不透明，用背景色填充。          logpen.lopnColor = RGB(rand()%256,rand()%256,rand()%256);         logpen.lopnStyle = PS_DASH;     logpen.lopnWidth = pt;  // lopnWidth是个POINT结构体。         hpen = CreatePenIndirect(&logpen);         SelectObject(hdc,hpen);     SetViewportOrgEx(hdc,rand()%cxClient,rand()%cyClient,NULL);         radius = _hypot(cxClient/2,cyClient/2);         for(i=0.0; i<TWO_PI; i+=TWO_PI/360)         {             MoveToEx(hdc,0,0,NULL);         LineTo(hdc,(int)(cos(i)*radius),(int)(sin(i)*radius));         }              logpen.lopnColor = RGB(rand()%256,rand()%256,rand()%256);         hpen = CreatePenIndirect(&logpen);         DeleteObject(SelectObject(hdc,hpen));         for(i=0.0; i<TWO_PI; i+=TWO_PI/360)         {             MoveToEx(hdc,0,0,NULL);         LineTo(hdc,(int)(cos(i)*radius),(int)(sin(i)*radius));         }              ReleaseDC(hwnd,hdc);         }     }     return msg.wParam; } LRESULT CALLBACK WinProc(HWND hwnd,UINT message,WPARAM wparam, LPARAM lparam) {         switch(message)     {     case WM_SIZE:          cxClient = LOWORD(lparam);      cyClient = HIWORD(lparam);      return 0;     case WM_DESTROY:                  DeleteObject(hpen);         PostQuitMessage(0);         return 0;     }     return DefWindowProc(hwnd,message,wparam,lparam); }

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