源代码：

#include "stdafx.h"
#include "GDIDemoWindowsDraft.h"

#define WINDOW_WIDTH    800
#define WINDOW_HEIGHT   600
#define WINDOW_TITLE    L"【Windows窗口测试——GDI练习】"

HDC g_hdc = NULL;           // 新增：全局设备环境句柄

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
BOOL Game_Init(HWND hwnd);      // 新增：函数，进行资源的初始化
VOID Game_Paint(HWND hwnd);     // 新增：函数，进行绘图代码的书写
BOOL Game_CleanUp(HWND hwnd);   // 新增：函数，进行资源的清理

//-----------------------------------【WinMain( )函数】--------------------------------------
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
    WNDCLASSEX wndClass = { 0 };
    wndClass.cbSize = sizeof(WNDCLASSEX);
    wndClass.style = CS_HREDRAW | CS_VREDRAW;
    wndClass.lpfnWndProc = WndProc;
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.hInstance = hInstance;
    wndClass.hIcon = (HICON)::LoadImage(NULL, L"icon.ico", IMAGE_ICON, 0, 0, LR_DEFAULTSIZE | LR_LOADFROMFILE);
    wndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndClass.hbrBackground = (HBRUSH)GetStockObject(GRAY_BRUSH);
    wndClass.lpszMenuName = NULL;
    wndClass.lpszClassName = L"ForTheDreamOfGameDevelop";


    if (!RegisterClassEx(&wndClass))
        return -1;


    HWND hwnd = CreateWindow(L"ForTheDreamOfGameDevelop",
        WINDOW_TITLE,
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        WINDOW_WIDTH,
        WINDOW_HEIGHT,
        NULL,
        NULL,
        hInstance,
        NULL);


    MoveWindow(hwnd, 250, 80, WINDOW_WIDTH, WINDOW_HEIGHT, true);
    ShowWindow(hwnd, nShowCmd);
    UpdateWindow(hwnd);

    // 新增：游戏资源的初始化，若初始化失败，弹出一个消息框，并返回FALSE
    if (!Game_Init(hwnd))
    {
        MessageBox(hwnd, L"资源初始化失败", L"消息窗口", 0);       //使用MessageBox函数，创建一个消息窗口
        return FALSE;
    }

    MSG msg = { 0 };
    while (msg.message != WM_QUIT)
    {
        if (PeekMessage(&msg, 0, 0, 0, PM_REMOVE))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    UnregisterClass(L"ForTheDreamOfGameDevelop", wndClass.hInstance);
    return 0;
}


//-----------------------------------【WndProc( )函数】--------------------------------------
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    PAINTSTRUCT paintStruct;                //定义一个PAINTSTRUCT结构体来记录一些绘制信息

    switch (message)                        //switch语句开始
    {
    case WM_PAINT:                          // 若是客户区重绘消息
        g_hdc = BeginPaint(hwnd, &paintStruct);     //指定窗口进行绘图工作的准备，并用将和绘图有关的信息填充到paintStruct结构体中。
        Game_Paint(hwnd);
        EndPaint(hwnd, &paintStruct);       //EndPaint函数标记指定窗口的绘画过程结束
        ValidateRect(hwnd, NULL);           // 更新客户区的显示
        break;                              //跳出该switch语句

    case WM_KEYDOWN:
        if (wParam == VK_ESCAPE)
            DestroyWindow(hwnd);
        break;

    case WM_DESTROY:                        //若是窗口销毁消息
        Game_CleanUp(hwnd);                 //调用自定义的资源清理函数Game_CleanUp（）进行退出前的资源清理
        PostQuitMessage(0);                 //向系统表明有个线程有终止请求。用来响应WM_DESTROY消息
        break;                              //跳出该switch语句

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

    return 0;
}

//-----------------------------------【Game_Init( )函数】--------------------------------------
//  描述：初始化函数，进行一些简单的初始化
//------------------------------------------------------------------------------------------------
BOOL Game_Init( HWND hwnd )
{
    g_hdc = GetDC(hwnd);
    Game_Paint( hwnd);
    return TRUE;
}

//-----------------------------------【Game_Paint( )函数】--------------------------------------
//  描述：绘制函数，在此函数中进行绘制操作
//--------------------------------------------------------------------------------------------------
VOID Game_Paint( HWND hwnd )
{

}

//-----------------------------------【Game_CleanUp( )函数】--------------------------------
//  描述：资源清理函数，在此函数中进行程序退出前资源的清理工作
//---------------------------------------------------------------------------------------------------
BOOL Game_CleanUp( HWND hwnd )
{
    ReleaseDC(hwnd,g_hdc);
    return TRUE;
}