C++屏幕水印实现遇到问题

C++用得不多，并且对 GDIPLUS 也不是很了解。想实现一个屏幕水印得工具，下面得代码运行后，Graphics 创建得对象背景非透明，并且程序无法正常关闭退出。大佬们帮忙看看，指定迷津

代码如下：

#include <Windows.h>
#include <gdiplus.h>
#include <string>

using namespace Gdiplus;
#pragma comment(lib, "gdiplus.lib")

const std::wstring watermarkText = L"Your Watermark Text";
const int watermarkFontSize = 38;
const int watermarkSpacing = 100;

void DrawWatermark(HDC hdc, int windowWidth, int windowHeight)
{
    // 初始化 GDI+
    GdiplusStartupInput gdiplusStartupInput;
    ULONG_PTR gdiplusToken;
    GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
    SetBkMode(hdc, TRANSPARENT);

    // 创建 Graphics 对象
    Graphics graphics(hdc);

    

    // 创建字体
    FontFamily fontFamily(L"Arial");
    Font font(&fontFamily, watermarkFontSize, FontStyleRegular, UnitPixel);

    // 设置文本颜色
    SolidBrush textBrush(Color(255, 0, 0, 0)); // 文本颜色为黑色

    // 获取文本尺寸
    RectF layoutRect;
    graphics.MeasureString(watermarkText.c_str(), -1, &font, PointF(0, 0), &layoutRect);

    // 计算水印文本块的总数以填满整个屏幕
    int numBlocksX = (windowWidth + watermarkSpacing) / (static_cast<int>(layoutRect.Width) + watermarkSpacing);
    int numBlocksY = (windowHeight + watermarkSpacing) / (static_cast<int>(layoutRect.Height) + watermarkSpacing);

    // 计算实际的间距
    int actualSpacingX = (windowWidth - numBlocksX * static_cast<int>(layoutRect.Width)) / (numBlocksX - 1);
    int actualSpacingY = (windowHeight - numBlocksY * static_cast<int>(layoutRect.Height)) / (numBlocksY - 1);

    // 保存当前的世界变换矩阵
    Matrix oldTransform;
    graphics.GetTransform(&oldTransform);

    // 绘制水印文本块
    for (int y = 0; y < numBlocksY; y++) {
        for (int x = 0; x < numBlocksX; x++) {
            int textX = x * (static_cast<int>(layoutRect.Width) + actualSpacingX);
            int textY = y * (static_cast<int>(layoutRect.Height) + actualSpacingY);

            // 移动 Graphics 对象到文本块位置
            graphics.ResetTransform();
            graphics.TranslateTransform(static_cast<float>(textX), static_cast<float>(textY));
            graphics.RotateTransform(-45.0f);

            // 绘制水印文本
            graphics.DrawString(watermarkText.c_str(), -1, &font, PointF(0, 0), &textBrush);

            // 恢复原始的世界变换矩阵
            graphics.SetTransform(&oldTransform);
        }
    }

    // 关闭 GDI+
    GdiplusShutdown(gdiplusToken);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE:
    {
        // 设置窗口样式为 WS_EX_LAYERED
        SetWindowLong(hwnd, GWL_EXSTYLE, GetWindowLong(hwnd, GWL_EXSTYLE) | WS_EX_LAYERED | WS_EX_TRANSPARENT);

        // 设置窗口为完全透明
        SetLayeredWindowAttributes(hwnd, RGB(0, 0, 0), 0, LWA_COLORKEY);

        // 设置窗口大小为屏幕大小
        int windowWidth = GetSystemMetrics(SM_CXSCREEN);
        int windowHeight = GetSystemMetrics(SM_CYSCREEN);
        SetWindowPos(hwnd, HWND_TOPMOST, 0, 0, windowWidth, windowHeight, SWP_SHOWWINDOW);

        break;
    }
    case WM_PAINT:
    {
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hwnd, &ps);
        int windowWidth = GetSystemMetrics(SM_CXSCREEN);
        int windowHeight = GetSystemMetrics(SM_CYSCREEN);

        // 绘制水印
        DrawWatermark(hdc, windowWidth, windowHeight);
        EndPaint(hwnd, &ps);

        break;
    }
    case WM_DESTROY:
    {
        PostQuitMessage(0);
        break;
    }
    default:
        return DefWindowProc(hwnd, message, wParam, lParam);
    }

    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASSEX wcex;
    ZeroMemory(&wcex, sizeof(WNDCLASSEX));
    wcex.cbSize = sizeof(WNDCLASSEX);
    wcex.lpfnWndProc = WndProc;
    wcex.hInstance = hInstance;
    wcex.lpszClassName = L"WatermarkWindowClass";
    RegisterClassEx(&wcex);

    HWND hwnd = CreateWindow(L"WatermarkWindowClass", L"", WS_POPUP, 0, 0, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN), NULL, NULL, hInstance, NULL);

    if (hwnd == NULL)
    {
        return 0;
    }

    ShowWindow(hwnd, nCmdShow);

    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return static_cast<int>(msg.wParam);
}