球与边框碰撞

//windows.h文件中包含应用程序中所需的数据类型和数据结构的定义
#include <windows.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);//窗口函数说明
//---------以下初始化窗口类--------------
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInst,LPSTR lpszCmdLine,int nCmdShow)
{
    HWND hwnd;
    MSG Msg;
    WNDCLASS wndclass;
    char lpszClassName[] = "窗口";     //窗口类名
    char lpszTitle[] = "My_Windows";    //窗口标题名

    //窗口类的定义
    wndclass.style = CS_HREDRAW | CS_VREDRAW;                  //窗口类型为默认类型
    wndclass.lpfnWndProc = WndProc;      //窗口处理函数为WndProc
    wndclass.cbClsExtra = 0;             //窗口类无扩展
    wndclass.cbWndExtra = 0;             //窗口实例无扩展
    wndclass.hInstance = hInstance;     //当前实例句柄

    wndclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);//窗口的最小化图标为默认图标
    wndclass.hCursor = LoadCursor( NULL, IDC_ARROW); //窗口 采用箭头光标
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH); //窗口 背景为 白色
    wndclass.lpszMenuName = NULL ; //窗口 中无菜单
    wndclass.lpszClassName = lpszClassName; //窗口类名为“窗口示例”
//-----------以下进行窗口类的注册
    if (!RegisterClass(&wndclass))//如果注册失败则发出警吿声音
    {
        MessageBeep (0);
        return FALSE;
    }

//创建窗口
    hwnd = CreateWindow(
                        lpszClassName, //窗口类名
                        lpszTitle,      //窗口实例的标题名
                        WS_OVERLAPPEDWINDOW, //窗口 的风格
                        CW_USEDEFAULT,
                        CW_USEDEFAULT,  //窗口左上角坐标为默认值
                        CW_USEDEFAULT,
                        CW_USEDEFAULT,  //窗口的髙和宽为默认值
                        NULL,           //此窗口无父窗口
                        NULL,           //此窗口无主菜单
                        hInstance,      //创建此窗口应用程序的当前句柄
                        NULL            //不使用该值
                        );



    ShowWindow( hwnd, nCmdShow);        //显示窗口
    UpdateWindow(hwnd);                 //绘制用户区
    while( GetMessage(&Msg, NULL, 0, 0)) //消息循环
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    return Msg.wParam;                  //程序终止时将信息返回系统
}
#define LR (rect.left+rect.right)
#define TD (rect.bottom+rect.top)
#define R 50
#define PI acos(-1)

//窗口函数
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    HDC hDC;
    HBRUSH hBrush;
    RECT rect;
    HPEN hPen;
    PAINTSTRUCT PtStr;
    POINT p, add;
    static int x, y;
    static int vx = 3, vy = 4;
    static int r = 5;
    static int uddis = 1;
    static int lrdis = 1;
    static int t;
    int nextx, nexty;

    COLORREF color[7] = {RGB(255,0,0), RGB(255,165,0), RGB(255,255,0), RGB(0,255,0), RGB(0,255,255), RGB(0,0,255), RGB(139,0,255)};

    switch(message)
    {
    case WM_CREATE:
        srand(time(NULL));
        x = rand() % 1000 + 10;
        y = rand() % 1000 + 10;
        vx = rand() % 50;
        vy = rand() % 50;
        r = rand() % 50;
        t = rand();
        if (t % 2)
            vx = -vx;
        t = rand();
        if (t % 2)
            vy = -vy;
        return 0;
    case WM_PAINT:
        GetClientRect(hWnd, &rect);
        hDC = BeginPaint(hWnd, &PtStr);
        hPen = CreatePen(PS_SOLID, 3, color[0]);
        hBrush = CreateHatchBrush(HS_BDIAGONAL, color[0]);

        SelectObject(hDC, hPen);
        SelectObject(hDC, hBrush);
        Ellipse(hDC, x-r, y-r, x+r, y+r);
        nextx = x + lrdis * vx;
        nexty = y + uddis *vy;
        if (nextx < rect.left+r)
        {
            nextx = rect.left + r;
            lrdis = -lrdis;
        }
        if (nexty < rect.top + r)
        {
            nexty = rect.top + r;
            uddis = -uddis;
        }
        if (nextx > rect.right - r)
        {
            nextx > rect.right - r;
            lrdis = -lrdis;
        }
        if (nexty > rect.bottom - r)
        {
            nexty = rect.bottom - r;
            uddis = -uddis;
        }
        x = nextx;
        y = nexty;
        DeleteObject(hPen);
        DeleteObject(hBrush);
        Sleep(50);
        InvalidateRect(hWnd, NULL, 1);

        EndPaint(hWnd, &PtStr);

        return 0;

    case WM_DESTROY:
        PostQuitMessage(0);                 //调用 PostQuitMessage 发出 WM_QUIT 消息
        return 0;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam); //默认时采用系统消息默认处理函数

    }

}