从不使用标签控件的对话框中获取文本？

Question

这是我之前的问题How to supress a dialog box an Inproc COM Server displays的延续。

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背景：

回顾一下我的情况：我有一个来自第 3 方的用 Delphi 编写的 Inproc COM 服务器。如果捕获特定类型的错误，我调用的函数之一将显示错误消息对话框。问题是我正在尝试批量处理数据，而我正在使用的数据源导致该错误对话框弹出很多（感谢我之前的问题的答案，它现在自动关闭并且我能够运行它完成，它会显示对话框并要求有人按 OK 9923 次）。进程阻塞，直到消息框关闭。

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问题：

我希望更好地记录错误对话框所说的内容。但是，任何获取对话框正文的尝试都失败了。

//Snip

private void StartWindowListener()
{
    //Queue the watcher on the message pump if we are not watching.
    if (_watcherRunning == false)
    {
        _watcherRunning = true;
        _dummyForm.BeginInvoke(new Action(() =>
        {
            _watcherRunning = false;

            //If we are not inside the com object don't enumerate.
            if (_insideCom == false) return;

            // Enumerate windows to find dialogs
            EnumThreadWndProc callback = new EnumThreadWndProc(CheckWindow);
            EnumThreadWindows(GetCurrentThreadId(), callback, IntPtr.Zero);
            GC.KeepAlive(callback);
        }));
    }
}

private bool CheckWindow(IntPtr hWnd, IntPtr lp)
{
    // Checks if hWnd is the expected dialog
    StringBuilder sb = new StringBuilder(260);
    GetClassName(hWnd, sb, sb.Capacity);
    if (sb.ToString() == "TMessageForm")
    {
        //This returns the dialog box's title
        GetWindowText(hWnd, sb, sb.Capacity);

        //This returns IntPtr.Zero
        var hDialogText = GetDlgItem(hWnd, 0xFFFF);
        if (hDialogText != IntPtr.Zero)
            GetWindowText(hDialogText, sb, sb.Capacity);

        //This returns a empty string
        GetDlgItemText(hWnd, 0xFFFF, sb, sb.Capacity);


        //Only sees the OK button.
        IntPtr hCtl = IntPtr.Zero;
        HashSet<IntPtr> seen = new HashSet<IntPtr>();
        while ((hCtl = GetNextDlgGroupItem(hWnd, hCtl, false)) != IntPtr.Zero)
        {
            //When we see the same control twice, break out of the loop.
            if (seen.Add(hCtl) == false)
                break;

            GetClassName(hCtl, sb, sb.Capacity);
            SendMessage(hCtl, WM_GETTEXT, sb.Capacity, sb)

            //Close the dialog by sending WM_CLOSE to the window
            SendMessage(hWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
        }

         //Snip...
    }
    return true;
}

//Snip...

// P/Invoke declarations
const int WM_CLOSE = 0x0010;
private delegate bool EnumThreadWndProc(IntPtr hWnd, IntPtr lp);
[DllImport("user32.dll")]
private static extern bool EnumThreadWindows(int tid, EnumThreadWndProc callback, IntPtr lp);
[DllImport("user32.dll")]
private static extern int GetClassName(IntPtr hWnd, StringBuilder buffer, int buflen);
[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);
[DllImport("kernel32.dll")]
private static extern int GetCurrentThreadId();

我想我可能在对话框开始添加文本之前中断了对话框（当我中断上面的代码时，它还没有完全绘制）。但是，在开始枚举之前在 StartWindowListener 中放置 Application.DoEvents 可以让对话框完全绘制，但我仍然得到与使用上述代码发布的结果相同的结果。

在对话框上执行 Ctrl-C 可以正常工作，因此我可以在紧要关头使用它，但由于我必须重复这 9923 次，我想避免以编程方式使用它。

还有其他方法可以尝试从消息框中获取文本吗？

Answer 1

感谢Sertac's comment 我发现Delphi 消息框中的文本不是窗口对象，它们是用'DrawText' 方法绘制的。我使用EasyHook 拦截了 Windows API 调用，现在我可以抓取我关心的文本了。

////It appears that DrawText always calls DrawTextEx so it is getting intercepted twice.
//// Only need to hook DrawTextEx
static EasyHook.LocalHook _drawTextExAHook;

//Snip...

public override void Run()
{
    //Snip...

    IntPtr drawTextExAPtr = EasyHook.LocalHook.GetProcAddress("user32", "DrawTextExA");
    _drawTextExAHook = EasyHook.LocalHook.Create(drawTextExAPtr, new DrawTextExDelegate(DrawTextEx_Hooked), null);

    //The COM stuff must be run in a STA Thread so we can intercept the message boxes that it throws up.
    var staThread = new Thread(() =>
        {
            try
            {
                var threadID = new[] { GetCurrentThreadId() };
                //Enable the hook on the current thread.
                _drawTextExAHook.ThreadACL.SetInclusiveACL(threadID);

                //Tell the dummy form to start ComThread
                _dummyForm = new DummyForm(ComThread);
                Application.Run(_dummyForm);
            }
            finally
            {
                if(_drawTextExAHook != null)
                    _drawTextExAHook.Dispose();
            }
        });
    staThread.SetApartmentState(ApartmentState.STA);
    staThread.Name = "Com Thread";
    staThread.Start();

    //Wait for the Com Thread to finish.
    staThread.Join();

}

//Snip...

private delegate int DrawTextExDelegate(IntPtr hdc, string lpchText, int cchText,
                ref Rect lprc, uint dwDTFormat, ref DRAWTEXTPARAMS lpDTParams);

private int DrawTextEx_Hooked(IntPtr hdc, string lpchText, int cchText, ref Rect lprc, 
                                     uint dwDTFormat, ref DRAWTEXTPARAMS lpDTParams)
{
    LogErrorText(lpchText);
    return DrawTextEx(hdc, lpchText, cchText, ref lprc, dwDTFormat, ref lpDTParams);
}

[DllImport("user32.dll")]
static extern int DrawTextEx(IntPtr hdc, string lpchText, int cchText,
                             ref Rect lprc, uint dwDTFormat, ref DRAWTEXTPARAMS lpDTParams);