WM_KEYDOWN，从 lparam 获取值？

Question

在 MSDN 上，对于 WM_KEYDOWN 定义，它说 lparam 的位包含：

Bits    Meaning
0-15    The repeat count for the current message. The value is the number of times the keystroke is autorepeated as a result of the user holding down the key. If the keystroke is held long enough, multiple messages are sent. However, the repeat count is not cumulative.
16-23   The scan code. The value depends on the OEM.
24  Indicates whether the key is an extended key, such as the right-hand ALT and CTRL keys that appear on an enhanced 101- or 102-key keyboard. The value is 1 if it is an extended key; otherwise, it is 0.
25-28   Reserved; do not use.
29  The context code. The value is always 0 for a WM_KEYDOWN message.
30  The previous key state. The value is 1 if the key is down before the message is sent, or it is zero if the key is up.
31  The transition state. The value is always 0 for a WM_KEYDOWN message.

(http://msdn.microsoft.com/en-us/library/ms646280%28VS.85%29.aspx)

所以我创建了一个内部结构如下的联合：

union KeyState
{
    LPARAM lparam;

    struct
    {
        unsigned nRepeatCount : 15;
        unsigned nScanCode : 8;
        unsigned nExtended : 1;
        unsigned nReserved : 4;
        unsigned nContext : 1;
        unsigned nPrev : 1;
        unsigned nTrans : 1;
    };
};

然后当我在我的编辑框上收到一条 wm_keydown 消息时，我会这样打印它：

if (msg == WM_KEYDOWN)
{
    std::tstringstream ss;

    KeyState ks;
    ks.lparam = lparam;

    ss << "Key: " << (TCHAR)wparam << ", Val: " << (UINT)wparam << ", nRepeatCount: " << ks.nRepeatCount << 
        ", nScanCode: " << ks.nScanCode << ", nExtended: " << ks.nExtended << ", nReserved: " << ks.nReserved << 
        ", nContext: " << ks.nContext << ", nPrev: " << ks.nPrev << ", nTrans: " << ks.nTrans;

    SetWindowText(hOut, ss.str().c_str());
}

我在编辑框中输入时返回的值似乎不正确，有时 nReserved 甚至为 1 或 0，并且 nRepeatCount 始终为 1，无论我是否按住键登录时间或者只是按随机键。

我做错了吗？如果是这样，从 LPARAM 获取这些值的理想方法是什么？

Answer 1

嗯，一方面 0-15 是 16 位，而不是 15。

Answer 2

是的，很容易出错（参见 500 的回答）。我会简单地使用位图和位移。

例如。 NRepeat = lparam & 0xFFFF;