c++ - WM_CHAR lParam 扩展 key (24 位)始终为 0

Question

我正在尝试获取扩展键状态

WNDPROC lpfnEditWndProc; 

//edit - hwnd of edit control
lpfnEditWndProc = (WNDPROC) SetWindowLong(edit, GWL_WNDPROC, (DWORD) SubClassProc); 


struct Bits {
    WORD nRepeatCount: 16;
    BYTE nScanCode : 8;
    BYTE nExtended : 1;
    BYTE nReserved : 4;
    BYTE nContext : 1;
    BYTE nPrevious : 1;
    BYTE nTransition : 1;
  };


union KeyInfo
{  
  LPARAM lParam;
  Bits bits;  
};


LRESULT CALLBACK SubClassProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) 
{
     switch (msg) { 
          case WM_CHAR: 
          {
              KeyInfo v;
              v.lParam = lParam;

              printf("nExtended = %d\n", v.bits.nExtended);
          }
          break;

     }

     return CallWindowProc(lpfnEditWndProc, hwnd, msg, wParam, lParam); 
}

nExtended 总是 == 0

我尝试以不同的方式获取信息，比如 (lParam << 24) & 1;

都一样 nExtended == 0

Win7 64 位，Visual Studio 2010

Answer 1

documentation for WM_CHAR说:

Because there is not necessarily a one-to-one correspondence between keys pressed and character messages generated, the information in the high-order word of the lParam parameter is generally not useful to applications. The information in the high-order word applies only to the most recent WM_KEYDOWN message that precedes the posting of the WM_CHAR message.

您必须处理 WM_KEYDOWN 和 WM_KEYUP 消息才能获得扩展 key 信息。