windows编程：画线，简单的碰撞检测，简单的帧率锁定

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <windowsx.h>
#include <mmsystem.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define WINDOW_CLASS_NAME "WINCLASS1"

#define WINDOW_WIDTH  640
#define WINDOW_HEIGHT 480

#define KEYDOWN(vk_code)    ((GetAsyncKeyState(vk_code) & 0x8000) ? 1:0)
#define KEYUP(vk_code)        ((GetAsyncKeyState(vk_code) & 0x8000) ? 0:1)

//全局变量
HWND main_window_handle = NULL;
HINSTANCE hInstance_App = NULL;

char buffer[80];

//窗口处理函数
LRESULT CALLBACK WindowProc(HWND hwnd,
    UINT msg,
    WPARAM wParam,
    LPARAM lPram)
{
    PAINTSTRUCT ps;
    HDC hdc;
    RECT rect;
    char buffer[80];
    switch (msg)
    {
    case WM_CREATE:
    {
                      return 0;
    }break;
    case WM_PAINT:
    {
                     hdc = GetDC(hwnd);
                     ReleaseDC(hwnd, hdc);
                     GetClientRect(hwnd, &rect);
                     ValidateRect(hwnd, &rect);

                     return 0;
    }break;
    case WM_CLOSE:
    {
                     if (IDYES != MessageBox(hwnd, "确实要退出应用程序？", "退出", MB_YESNO | MB_ICONEXCLAMATION))
                     {
                         return 0;
                     }
                     else
                     {
                         PostQuitMessage(0);
                     }
    }break;
    case WM_SIZE:
    {

    }break;
    case WM_DESTROY:
    {
                       PostQuitMessage(0);
                       return 0;
    }break;
    default:break;
    }
    return DefWindowProc(hwnd, msg, wParam, lPram);
}
void GameMain()
{
    return;
}
int WINAPI WinMain(HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    LPSTR lpCmdLine,
    int nCmdShow)
{
    //定义窗口类
    WNDCLASSEX winClass;
    HWND hWnd;
    MSG msg;

    HPEN pen = NULL;
    int color_change_count = 100;

    //填充窗口类的各成员
    winClass.cbSize = sizeof(WNDCLASSEX);
    winClass.style = CS_DBLCLKS | CS_OWNDC | CS_HREDRAW | CS_VREDRAW;
    winClass.lpfnWndProc = WindowProc;    //窗口消息处理函数
    winClass.cbClsExtra = 0;
    winClass.cbWndExtra = 0;
    winClass.hInstance = hInstance;
    winClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    winClass.hCursor = LoadCursor(NULL, IDC_ARROW);
    winClass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    winClass.lpszMenuName = NULL;
    winClass.lpszClassName = WINDOW_CLASS_NAME;        //窗口类名
    winClass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

    //保存实例句柄到全局变量
    hInstance_App = hInstance;

    //注册窗口类
    if (!RegisterClassEx(&winClass))
    {
        return 0;
    }

    //创建窗口类的一个成员
    if (!(hWnd = CreateWindowEx(NULL,
        WINDOW_CLASS_NAME,
        "时间锁定的屏幕保护程序",
        WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        200, 200,
        WINDOW_WIDTH, WINDOW_HEIGHT,
        NULL,
        NULL,
        hInstance,
        NULL)))
    {
        return 0;
    }

    //保存窗体句柄到全局变量中
    main_window_handle = hWnd;

    //得到设备上下文
    HDC hdc = GetDC(hWnd);

    //设置随机数生成器的种子
    srand(GetTickCount());

    //线段终点坐标
    int x1 = rand() % WINDOW_WIDTH;
    int y1 = rand() % WINDOW_HEIGHT;
    int x2 = rand() % WINDOW_WIDTH;
    int y2 = rand() % WINDOW_HEIGHT;

    //线段终点的速度
    int x1v = -4 + rand() % 8;
    int y1v = -4 + rand() % 8;
    int x2v = -4 + rand() % 8;
    int y2v = -4 + rand() % 8;

    //消息循环
    while (TRUE)
    {
        DWORD start_time = GetTickCount();

        if (PeekMessage(&msg, hWnd, 0, 0, PM_REMOVE))
        {
            if (msg.message == WM_QUIT)
            {
                break;
            }
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        //100次变换一次颜色
        if (++color_change_count >= 100)
        {
            color_change_count = 0;
            if (pen)
            {
                DeleteObject(pen);
            }
            pen = CreatePen(PS_SOLID, 1, RGB(rand() % 256, rand() % 256, rand() % 256));
            SelectObject(hdc, pen);
        }
        //移动线段终点
        x1 += x1v;
        y1 += y1v;

        x2 += x2v;
        y2 += y2v;

        //碰撞检测，看是否碰到窗体的边界
        if (x1<0 || x1>WINDOW_WIDTH)
        {
            x1v = -x1v;
            x1 += x1v;
        }
        if (y1<0 || y1>WINDOW_HEIGHT)
        {
            y1v = -y1v;
            y1 += y1v;
        }

        if (x2<0 || x2>WINDOW_WIDTH)
        {
            x2v = -x2v;
            x2 += x2v;
        }
        if (y2<0 || y2>WINDOW_HEIGHT)
        {
            y2v = -y2v;
            y2 += y2v;
        }

        MoveToEx(hdc, x1, y1,NULL);
        LineTo(hdc, x2, y2);

        //锁定帧率为30fps,1/30秒，约等于33毫秒。
        while (GetTickCount() - start_time < 33);
        //如果用户按了ESC，发送WM_CLOSE消息。退出程序。
        if (KEYDOWN(VK_ESCAPE))
            SendMessage(hWnd, WM_CLOSE, 0, 0);
    }
    ReleaseDC(hWnd, hdc);
    return msg.wParam;
}