c++ - 带有自定义数据的 SetWinEventHook

Question

我正在使用 SetWinEventHook Hook 来检测编辑控件的选择。在事件钩子(Hook)回调函数中，有没有办法指定自定义数据？在我的例子中，自定义数据将是 VKeyboard 实例。

请查看代码以更好地描述我想要实现的目标。

class VKeyboard
{
public:
    static void CALLBACK winEventProc(HWINEVENTHOOK hWinEventHook, DWORD  event, HWND hwnd, LONG idObject, LONG idChild, DWORD dwEventThread, DWORD dwmsEventTime)
    {
        // Somehow access VKeyboard instance?
        VKeyboard* keyboard = ??;

        IAccessible* pAcc = NULL;
        VARIANT varChild;
        HRESULT hr = AccessibleObjectFromEvent(hwnd, idObject, idChild, &pAcc, &varChild);

        if ((hr == S_OK) && (pAcc != NULL))
        {
            VARIANT varRole;
            hr = pAcc->get_accRole(varChild, &varRole);

            // if user selects a edit control: show window
            if ((hr == S_OK) && (varRole.vt == VT_I4) && (varRole.lVal == ROLE_SYSTEM_TEXT))
                ShowWindow(keyboard->mainHwnd, SW_SHOW);
            else ShowWindow(keyboard->mainHwnd, SW_HIDE);

            pAcc->Release();
        }
    }

    VKeyboard() 
    {
        SetWinEventHook(EVENT_OBJECT_FOCUS, EVENT_OBJECT_FOCUS, NULL, (WINEVENTPROC)&winEventProc, 0, 0, WINEVENT_SKIPOWNPROCESS);


        SetWindowLongPtr (mainHwnd, GWLP_USERDATA, (LONG_PTR)this);
    }

    HWND mainHwnd;
}

Answer 1

由于您的 Hook 回调是作为 Out of Context hook 实现的, 它总是在调用 SetWinEventHook() 的线程的上下文中调用，即使在 Hook 其他进程的事件时也是如此。因此，您可以使用 Thread Local Storage ，甚至只是一个全局变量，来存储您的 VKeyboard 对象指针。前提是您只需要一个 VKeyboard 实例。

class VKeyboard
{
private:
    HWINEVENTHOOK hHook;
    static VKeyboard *pKeyboard;

    static void CALLBACK winEventProc(HWINEVENTHOOK hWinEventHook, DWORD  event, HWND hwnd, LONG idObject, LONG idChild, DWORD dwEventThread, DWORD dwmsEventTime)
    {
        IAccessible* pAcc = NULL;
        VARIANT varChild;
        HRESULT hr = AccessibleObjectFromEvent(hwnd, idObject, idChild, &pAcc, &varChild);

        if ((hr == S_OK) && (pAcc != NULL))
        {
            VARIANT varRole;
            hr = pAcc->get_accRole(varChild, &varRole);

            // if user selects a edit control: show window
            if ((hr == S_OK) && (varRole.vt == VT_I4) && (varRole.lVal == ROLE_SYSTEM_TEXT))
                ShowWindow(pKeyboard->mainHwnd, SW_SHOW);
            else ShowWindow(pKeyboard->mainHwnd, SW_HIDE);

            pAcc->Release();
        }
    }

    VKeyboard() 
    {
        hHook = SetWinEventHook(EVENT_OBJECT_FOCUS, EVENT_OBJECT_FOCUS, NULL, &winEventProc, 0, 0, WINEVENT_OUTOFCONTEXT | WINEVENT_SKIPOWNPROCESS);

        mainHwnd = ...;
        SetWindowLongPtr (mainHwnd, GWLP_USERDATA, (LONG_PTR)this);
        pKeyboard = this;
    }

    ~VKeyboard()
    {
        UnhookWinEvent(hHook);
        pKeyboard = NULL;
    }

    HWND mainHwnd;
};