Win32 子类化 - 关于消息

Question

所以我正在练习在 Win32 中对预定义的窗口类进行子类化，这样我就可以为预定义的类定义我自己的自定义消息 proc（例如，为按钮类制作自定义 WndProc）并且我让它大部分工作但我无法将 WM_COMMAND 消息自动发送到新消息进程。我可以在 WM_COMMAND 的父窗口中设置一个案例并检查 wParam，然后为发送 WM_COMMAND 消息的子窗口调用相应的新消息 proc，但我希望像所有其他命令一样自动完成此操作。据我所知，我在自定义消息过程中尝试过的所有其他 WM_ 都会从父窗口的消息过程中自动传递给它，但是除非我明确重定向它们，否则 WM_COMMAND 消息不会。我有一种感觉 WM_COMMAND 消息在子类化我设置它的方式时总是会发送到父窗口，但是如果有人可以解释为什么会这样或者我需要做什么来引导所有属于我定义的自定义 WndProc 的按钮窗口，将不胜感激。

代码：

#include <Windows.h>
#include <windowsx.h>

#define IDC_BUTTON   0


LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
LRESULT CALLBACK WndProcButton (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

HWND    g_hwndButton            = NULL;
WNDPROC g_wndProcButtonOrigianl = NULL;
BOOL    g_bSeeingMouse          = FALSE;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    LPSTR szCmdLine, int iCmdShow)
{
     static TCHAR szClassName[] = TEXT ("HelloWin") ;
     HWND         hwnd ;
     MSG          msg ;
     WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szClassName ;

     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("This program requires Windows NT!"), 
                      szClassName, MB_ICONERROR) ;
          return 0 ;
     }

     hwnd = CreateWindow (szClassName,                // window class name
                          TEXT ("The Hello Program"), // window caption
                          WS_OVERLAPPEDWINDOW,        // window style
                          CW_USEDEFAULT,              // initial x position
                          CW_USEDEFAULT,              // initial y position
                          CW_USEDEFAULT,              // initial x size
                          CW_USEDEFAULT,              // initial y size
                          NULL,                       // parent window handle
                          NULL,                       // window menu handle
                          hInstance,                  // program instance handle
                          NULL) ;                     // creation parameters

     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;

     while (GetMessage (&msg, NULL, 0, 0))
     {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
     }
     return msg.wParam ;
}


LRESULT CALLBACK WndProcButton (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch( message )
    {
    case WM_COMMAND:
        MessageBox( hwnd, TEXT( "Test box" ), TEXT( "Test box" ), MB_OK );
        SetFocus( g_hwndButton );
        break;
    default:
        if( !g_bSeeingMouse && GetCapture() == hwnd )
        {
            g_bSeeingMouse = TRUE;
            SetWindowText( hwnd, L"Ok +mouse" );
        }
        else if( g_bSeeingMouse && GetCapture() != hwnd )
        {
            g_bSeeingMouse = FALSE;
            SetWindowText( hwnd, L"Ok" );
        }
        break;
    }
    return CallWindowProc( g_wndProcButtonOrigianl, hwnd, message, wParam, lParam );
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     HDC         hdc ;
     PAINTSTRUCT ps ;
     RECT        rect ;

     switch (message)
     {
     case WM_CREATE:
         g_hwndButton = CreateWindow( L"Button",                                            // predefined class
                                      L"Ok",                                                // button text
                                      ( WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON ),         // styles
                                      // Size and poition values are given explicitly, because
                                      // the CW_USEDEFAULT constant gives zero values for buttons.
                                      10,                                                   // starting x position
                                      10,                                                   // starting y position
                                      100,                                                  // button width
                                      30,                                                   // button height
                                      hwnd,                                                 // parent window
                                      (HMENU)IDC_BUTTON,                                    // no menu
                                      (HINSTANCE)GetWindowLongPtr( hwnd, GWLP_HINSTANCE ),
                                      NULL );                                               // pointer not needed
         SetFocus( g_hwndButton );
         g_wndProcButtonOrigianl = (WNDPROC)SetWindowLongPtr( g_hwndButton, GWLP_WNDPROC, (LONG_PTR)WndProcButton );
          return 0 ;

     case WM_PAINT:
          hdc = BeginPaint (hwnd, &ps) ;

          GetClientRect (hwnd, &rect) ;

          DrawText (hdc, TEXT ("Hello, Windows 98!"), -1, &rect,
                    DT_SINGLELINE | DT_CENTER | DT_VCENTER) ;

          EndPaint (hwnd, &ps) ;
          return 0 ;

     case WM_DESTROY:
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

Answer 1

按照设计，WM_COMMAND 和 WM_NOTIFY 消息被发送到控件的父窗口。没有办法让 API 自动将它们发送到生成它们的控件。父窗口必须根据需要处理或转发它们。这是无法避免的。

在最初由 Borland 编写并现在归 Embarcadero 所有的 VCL 框架中，它使用一个简单的系统来转发此类消息。当任何父窗口接收到这些消息之一时，它会将消息 ID 增加一个将消息放入用户定义范围的偏移量，然后将消息转发到消息中指定的子 HWND。所以WM_COMMAND变成CN_COMMAND和WM_NOTIFY变成CN_NOTIFY，子控件的窗口过程可以查找。

例如：

#define MY_COMMAND  (WM_COMMAND + some_offset)
#define MY_NOTIFY   (WM_NOTIFY + some_offset)

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     switch (message)
     {
     case WM_COMMAND:
         if (lParam != 0)
             SendMessage((HWND)lParam, MY_COMMAND, wParam, lParam);
         return 0;

     case WM_NOTIFY:
         SendMessage(((NMHDR*)lParam)->hwndFrom, MY_NOTIFY, wParam, lParam);
         return 0;

     ...
     }

     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

LRESULT CALLBACK WndProcButton (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch( message )
    {
    case MY_COMMAND:
        ...
    case MY_NOTIFY:
        ...
    }

    return CallWindowProc( g_wndProcButtonOrigianl, hwnd, message, wParam, lParam );
}