WM_DESTROY没有在包装的WndProc中调用

Question

我已经采用了你在那里找到的典型解决方案，以便使用WNDPROC作为对象方法，但看起来WM_DESTROY消息不会发送到对象窗口自己的WNDPROC，并且程序在关闭窗口后不会退出。

我的窗口类看起来像这样（删除了不相关的代码）：

class MyWindow : MyApp
{
public:
    MyWindow();
    void Create(void);
    LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
private:
    HWND _hWnd;
};

void MyWindow::Create()
{
    // Here I register my class and call CreateWindowEx
    // Everything works fine so far

    // Part of the code where I assign the static WNDPROC
    WNDCLASSEXW wcex;

    wcex.cbSize = sizeof(WNDCLASSEX);
    wcex.style = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc = MyApp::WndProc;
    wcex.cbClsExtra = 0;
    wcex.cbWndExtra = 0;
    wcex.hInstance = this->Instance;
    wcex.hIcon = LoadIcon(this->Instance, MAKEINTRESOURCE(32512));
    wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
    wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wcex.lpszMenuName = NULL;
    wcex.lpszClassName = "MyWindowClass";
    wcex.hIconSm = LoadIcon(this->Instance, MAKEINTRESOURCE(32512));

    RegisterClassExW(&wcex);

    this->_hWnd = CreateWindowExW(
        WS_EX_TOOLWINDOW | WS_EX_TOOLWINDOW,
        wcex.lpszClassName,
        "Window Title",
        WS_POPUP,
        10, 10,
        600, 400,
        nullptr, 
        nullptr, 
        this->Instance,
        nullptr
    );

    ShowWindow(this->_hWnd, SW_SHOW);
    UpdateWindow(this->_hWnd);
}

LRESULT CALLBACK MyWindow::WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    case WM_CREATE:
    {
        // If I place a MessageBox here, it shows up
    }
    break;
    case WM_DESTROY:
        // It never gets to this point

        // Decrease windows count
        this->WindowsCount--;

        PostQuitMessage(0);
        break;
    break;
    default:
        return DefWindowProc(hWnd, msg, wParam, lParam);
    }
    return 0;
}

现在是一个包含静态WNDPROC的类，它在创建时分配

class MyApp
{
public:
    static HINSTANCE Instance;
    static int WindowsCount;

    MyApp();
    static LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
};

和实施

LRESULT CALLBACK MyApp::WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    // Window object
    MyWindow* myWindow = NULL;

    if (msg == WM_CREATE) {
        myWindow = reinterpret_cast<MyWindow *>(((LPCREATESTRUCT)lParam)->lpCreateParams);
        SetWindowLongPtr(hWnd, GWLP_USERDATA, (LONG_PTR)myWindow);
    }
    else {
        myWindow = reinterpret_cast<MyWindow *>(GetWindowLongPtr(hWnd, GWLP_USERDATA));
    }

    // If window not identified, identify now
    if (myWindow) {
        return myWindow->WndProc(hWnd, msg, wParam, lParam);
    }

    // Call window object's processor
    return DefWindowProc(hWnd, msg, wParam, lParam);
}

WM_CLOSE消息也没有捕获。我真的不明白为什么不传递这些消息

Answer 1

你正在将lpParam的CreateWindowEx()参数设置为nullptr，所以myWindow在nullptr中始终是MyApp::WndProc()，因此MyWindow::WndProc()永远不会被调用。你需要通过this而不是nullptr。

在调用RegisterClassExW() / CreateWindowEx()之前，你也没有进行任何错误检查以确保ShowWindow()和UpdateWindow()成功。

另外，考虑使用SetWindowSubclass()而不是(Get|Set)WindowLongPtr(GWLP_USERDATA)。请参阅MSDN上的Subclassing Controls和Raymond Chen关于Safer Subclassing的博客文章。