使用gdi在winapi窗口中更新运行时的颜色

#include <windows.h>

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HBRUSH hBrush = NULL;
    static COLORREF color = RGB(255, 0, 0); // 初始颜色为红色

    switch (message)
    {
    case WM_CREATE:
        hBrush = CreateSolidBrush(color);
        break;
    case WM_MOUSEMOVE:
        // 更新颜色为鼠标所在位置的RGB值
        color = RGB(GetRValue(lParam), GetGValue(lParam), GetBValue(lParam));
        DeleteObject(hBrush);
        hBrush = CreateSolidBrush(color);
        InvalidateRect(hWnd, NULL, TRUE); // 使窗口无效，触发重绘
        break;
    case WM_PAINT:
    {
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hWnd, &ps);
        SelectObject(hdc, hBrush);
        RECT rect;
        GetClientRect(hWnd, &rect);
        FillRect(hdc, &rect, hBrush);
        EndPaint(hWnd, &ps);
        break;
    }
    case WM_DESTROY:
        DeleteObject(hBrush);
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    // 注册窗口类
    WNDCLASSEX wcex;
    wcex.cbSize = sizeof(WNDCLASSEX);
    wcex.style = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc = WndProc;
    wcex.cbClsExtra = 0;
    wcex.cbWndExtra = 0;
    wcex.hInstance = hInstance;
    wcex.hIcon = LoadIcon(hInstance, IDI_APPLICATION);
    wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wcex.lpszMenuName = NULL;
    wcex.lpszClassName = "MyWindowClass";
    wcex.hIconSm = LoadIcon(wcex.hInstance, IDI_APPLICATION);

    if (!RegisterClassEx(&wcex))
    {
        MessageBox(NULL, "窗口类注册失败！", "错误", MB_ICONERROR);
        return 1;
    }

    // 创建窗口
    HWND hWnd = CreateWindow("MyWindowClass", "运行时颜色更新示例", WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 800, 600, NULL, NULL, hInstance, NULL);

    if (!hWnd)
    {
        MessageBox(NULL, "窗口创建失败！", "错误", MB_ICONERROR);
        return 1;
    }

    // 显示窗口
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

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

    return (int)msg.wParam;
}