根据以下要求用C++写windows代码：创建一个简单窗口， 按下鼠标左键，同时按下键盘上的ctrl键，拖动鼠标，在用户区上画出一个矩形，矩形左上角以初始按下鼠标的点，右下角为鼠标当前位置，放开鼠标，窗口用户区显示一个最后的矩形。按下键盘的‘l’(英文字母L的小写)，矩形放大，按下‘s’键，矩形缩小，并能用方向键实现所画矩形按相应方向移动。

以下是实现要求的C++代码：

#include <Windows.h>

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    // 注册窗口类
    WNDCLASS wc = {};
    wc.lpfnWndProc = WndProc;
    wc.hInstance = hInstance;
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.lpszClassName = "MyWindowClass";
    RegisterClass(&wc);

    // 创建窗口
    HWND hwnd = CreateWindow("MyWindowClass", "My Window", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 640, 480, NULL, NULL, hInstance, NULL);
    ShowWindow(hwnd, nCmdShow);

    // 进入消息循环
    MSG msg = {};
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    static BOOL bDrawRect = FALSE; // 是否正在绘制矩形
    static BOOL bCtrlDown = FALSE; // Ctrl键是否按下
    static int nDrawMode = 0; // 绘制模式，0为普通模式，1为放大模式，2为缩小模式
    static RECT rcDraw = {}; // 绘制矩形的位置和大小

    switch (msg)
    {
    case WM_LBUTTONDOWN: // 鼠标左键按下
        if (bCtrlDown)
        {
            // 记录绘制矩形的左上角位置
            rcDraw.left = LOWORD(lParam);
            rcDraw.top = HIWORD(lParam);
            bDrawRect = TRUE;
        }
        break;

    case WM_MOUSEMOVE: // 鼠标移动
        if (bDrawRect)
        {
            // 记录绘制矩形的右下角位置
            rcDraw.right = LOWORD(lParam);
            rcDraw.bottom = HIWORD(lParam);

            // 更新窗口客户区
            InvalidateRect(hwnd, NULL, TRUE);
        }
        break;

    case WM_LBUTTONUP: // 鼠标左键放开
        if (bDrawRect)
        {
            // 记录绘制矩形的右下角位置
            rcDraw.right = LOWORD(lParam);
            rcDraw.bottom = HIWORD(lParam);

            // 更新窗口客户区
            InvalidateRect(hwnd, NULL, TRUE);

            bDrawRect = FALSE;
        }
        break;

    case WM_KEYDOWN: // 键盘按下
        switch (wParam)
        {
        case VK_CONTROL: // Ctrl键按下
            bCtrlDown = TRUE;
            break;

        case 'l': // L键按下
            nDrawMode = 1;
            break;

        case 's': // S键按下
            nDrawMode = 2;
            break;

        case VK_LEFT: // 左箭头键按下
            if (bDrawRect)
            {
                OffsetRect(&rcDraw, -1, 0);
                InvalidateRect(hwnd, NULL, TRUE);
            }
            break;

        case VK_RIGHT: // 右箭头键按下
            if (bDrawRect)
            {
                OffsetRect(&rcDraw, 1, 0);
                InvalidateRect(hwnd, NULL, TRUE);
            }
            break;

        case VK_UP: // 上箭头键按下
            if (bDrawRect)
            {
                OffsetRect(&rcDraw, 0, -1);
                InvalidateRect(hwnd, NULL, TRUE);
            }
            break;

        case VK_DOWN: // 下箭头键按下
            if (bDrawRect)
            {
                OffsetRect(&rcDraw, 0, 1);
                InvalidateRect(hwnd, NULL, TRUE);
            }
            break;
        }
        break;

    case WM_KEYUP: // 键盘放开
        switch (wParam)
        {
        case VK_CONTROL: // Ctrl键放开
            bCtrlDown = FALSE;
            break;

        case 'l': // L键放开
        case 's': // S键放开
            nDrawMode = 0;
            InvalidateRect(hwnd, NULL, TRUE);
            break;
        }
        break;

    case WM_PAINT: // 绘制窗口
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hwnd, &ps);

            if (bDrawRect) // 绘制正在绘制的矩形
            {
                if (nDrawMode == 1) // 放大模式
                {
                    int nWidth = rcDraw.right - rcDraw.left;
                    int nHeight = rcDraw.bottom - rcDraw.top;

                    rcDraw.left -= nWidth / 4;
                    rcDraw.top -= nHeight / 4;
                    rcDraw.right += nWidth / 4;
                    rcDraw.bottom += nHeight / 4;
                }
                else if (nDrawMode == 2) // 缩小模式
                {
                    int nWidth = rcDraw.right - rcDraw.left;
                    int nHeight = rcDraw.bottom - rcDraw.top;

                    rcDraw.left += nWidth / 4;
                    rcDraw.top += nHeight / 4;
                    rcDraw.right -= nWidth / 4;
                    rcDraw.bottom -= nHeight / 4;
                }

                // 绘制矩形
                DrawFocusRect(hdc, &rcDraw);
            }
            else // 绘制最后的矩形
            {
                // 绘制矩形
                RECT rc = {100, 100, 200, 200};
                DrawFocusRect(hdc, &rc);
            }

            EndPaint(hwnd, &ps);
        }
        break;

    case WM_DESTROY: // 窗口关闭
        PostQuitMessage(0);
        break;

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

    return 0;
}