键盘钩子改变按键的行为

发布于 2024-09-15 14:36:21 字数 1958 浏览 4 评论 0原文

我正在创建一个程序，该程序安装一个键盘挂钩来捕获所有按键并显示一些与它们相关的文本。

然而，我遇到了一个障碍，那就是安装挂钩后一些按键会改变行为。

我会考虑发布一个小型但完整的测试程序，但现在我只描述问题。

该问题出现在 Windows 7 64 位、.NET 4.0（一个 C# 程序）中。我认为这些都不重要。

我的钩子通过 SetWindowsHookEx 自行安装，然后处理系统中处理的所有密钥。

如果钩子方法只是返回，或者对键进行最少的处理（我将在一秒钟内发布改变行为的内容），则键盘将按程序中的预期运行。

但是，如果我从 User32.dll 调用此函数 ToAscii 来确定键盘上的 OemTilde 或类似键实际上是哪个键，则任何“覆盖下一个键”的键都会停止运行。我不知道这些键的正确名称，但是两个撇号类型“和”，以及~和“，停止工作。

例如，如果我点击 ~ 然后点击 N，它会显示如下：

没有安装键盘钩子： ñ
安装键盘钩子： n （注意上面没有 ~）

有没有人知道为什么会发生这种情况以及如何解决这个问题？

现在，我将满足于在其他程序中正确处理按键，即使这意味着我无法在自己的程序中正确检测到正确的按键序列。

更多信息：

如果我调用 ToAscii 函数作为挂钩方法的一部分，则会出现不同的问题。像 ¡ 这样的键被处理两次，即。如果我点击一次 ¡，记事本会收到两个 ¡¡ 字符，点击 N 现在只会添加 N 。

但是，如果我使用 BeginInvoke 在单独的线程上处理按键，则从键盘钩子方法返回后，会出现第一个问题。

我的程序可能有点特别：

我不使用键盘状态（即，我传递的“键状态”256 字节数组只是充满 0）
我不关心死键（在某种意义上）我的程序不会处理它们，我非常关心它们，我不希望我的程序使它们对系统的其余部分毫无用处）

因此，我的代码最终如下所示：

private bool IsDeadKey(uint key)
{
    return ((Hook.Interop.MapVirtualKey(key, 2) & 2147483648) == 2147483648);
}

void _Hook_KeyDown_Async(KeyDownEventArgs e)
{
    var inBuffer = new byte[2];
    char key = '\0';
    if (!IsDeadKey((uint)e.KeyCode))
    {
        int ascii = Hook.Interop.ToAscii((int) e.KeyCode,
                                            e.ScanCode,
                                            _KeyState,
                                            inBuffer,
                                            e.Flags);
        if (ascii == 1)
        {
            key = Char.ToUpper((char) inBuffer[0]);
        }
    }

    BeginInvoke(
        new Action<Keys, Boolean, Boolean, Boolean, Char>(ProcessKeyboardEvent),
        e.KeyCode, e.Control, e.Shift, e.Alt, key);
}

原文

I'm creating a program that installs a keyboard hook to capture all keys and display some text related to them.

However, I've hit upon a snag, and that is some keys change behavior when the hook is installed.

I'll see about posting a small, but complete, test program, but for now I'll just describe the problem.

The problem exhibits itself on Windows 7 64-bit, in .NET 4.0, a C# program. I assume none of this matters.

My hook installs itself via SetWindowsHookEx and then handles all keys processed in the system.

If the hook method simply returns, or does minimal processing of the key (I'll post what changes the behavior in a second), the keyboard functions as expected in programs.

However, if I call this function, ToAscii from User32.dll, to figure out which key on my keyboard OemTilde or similar really is, then any key that "overlays the next key" stops functioning. I don't know the correct name for such keys, but the two apostrophe-types, `` and ´, as well as~and¨`, stops functioning.

For instance, if I hit ~ and then N, it displays as follows:

Without keyboard hook installed: ñ
With keyboard hook installed: n (notice no ~ above)

Does anyone know why this happens and how I can fix this problem?

For now I'll settle for just handling the keys correctly in other programs, even if that means that I won't be able to correctly detect the right key sequences in my own program.

Some more information:

If I call the ToAscii function as part of the hook method, then a different problem occurs. Keys like ¨ are processed twice, ie. if I hit the ¨ once, Notepad receives two ¨¨ characters, and hitting N now just adds the N.

However, if I use BeginInvoke to process the key on a separate thread, after returning from the keyboard hook method, the first problem occurs.

My program is probably a bit special in that:

I don't use keyboard state (ie. the "Key state" 256-byte array I pass around is just full of 0's)
I don't care about dead keys (in the sense that my program won't process them, I care just enough about them that I don't want my program to render them useless to the rest of the system)

As such, my code ended up looking as follows:

private bool IsDeadKey(uint key)
{
    return ((Hook.Interop.MapVirtualKey(key, 2) & 2147483648) == 2147483648);
}

void _Hook_KeyDown_Async(KeyDownEventArgs e)
{
    var inBuffer = new byte[2];
    char key = '\0';
    if (!IsDeadKey((uint)e.KeyCode))
    {
        int ascii = Hook.Interop.ToAscii((int) e.KeyCode,
                                            e.ScanCode,
                                            _KeyState,
                                            inBuffer,
                                            e.Flags);
        if (ascii == 1)
        {
            key = Char.ToUpper((char) inBuffer[0]);
        }
    }

    BeginInvoke(
        new Action<Keys, Boolean, Boolean, Boolean, Char>(ProcessKeyboardEvent),
        e.KeyCode, e.Control, e.Shift, e.Alt, key);
}

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牵你的手，一向走下去 2024-09-22 14:36:21

这些密钥称为死密钥，您也许可以解决通过删除对 ToAscii 的调用来解决这个问题。另请参阅以下相关主题：

键盘挂钩中的 ToAscii/ToUnicode 会被破坏死键。

更新：我还没有看到你的代码，但是在处理 KeyboardProc回调函数，可以检查一下当code时传递键盘消息吗参数小于0？文档说：

代码 [in] int
挂钩过程用来确定如何处理消息的代码。 如果code小于零，钩子过程必须将消息传递给CallNextHookEx函数而不进行进一步处理，并且应该返回CallNextHookEx<返回的值/代码>。

MSDN 中有一个设置托管挂钩的示例:

if (nCode < 0)
{
    return CallNextHookEx(hHook, nCode, wParam, lParam);
}
else
{
    // process message here

    return CallNextHookEx(hHook, nCode, wParam, lParam); 
}

These keys are called dead keys and you might be able to solve the problem by removing the call to ToAscii. See also the following related thread:

ToAscii/ToUnicode in a keyboard hook destroys dead keys.

Update: I haven't seen your code, but when processing the parameters of the KeyboardProc callback function, can you check that you pass the keyboard message on when the code parameter is less than 0? The documentation says:

code [in] int
A code the hook procedure uses to determine how to process the message. If code is less than zero, the hook procedure must pass the message to the CallNextHookEx function without further processing and should return the value returned by CallNextHookEx.

There is a sample for setting up a managed hook in MSDN:

if (nCode < 0)
{
    return CallNextHookEx(hHook, nCode, wParam, lParam);
}
else
{
    // process message here

    return CallNextHookEx(hHook, nCode, wParam, lParam); 
}

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