关于菜单项消息的返回值问题

Question

case WM_COMMAND:
               // Messages from edit control
          
          if (lParam && LOWORD (wParam) == EDITID)
          {
               switch (HIWORD (wParam))
               {
               case EN_UPDATE :
                    bNeedSave = TRUE ;
                    return 0 ;
                    
               case EN_ERRSPACE :
               case EN_MAXTEXT :
                    MessageBox (hwnd, TEXT ("Edit control out of space."),
                                szAppName, MB_OK | MB_ICONSTOP) ;
                    return 0 ;
               }
               break ;
          }
          
          switch (LOWORD (wParam))
          {
               // Messages from File menu
               
          case IDM_FILE_NEW:
               if (bNeedSave && IDCANCEL == AskAboutSave (hwnd, szTitleName))
                    return 0 ;
               
               SetWindowText (hwndEdit, TEXT ("\0")) ;
               szFileName[0]  = '\0' ;
               szTitleName[0] = '\0' ;
               DoCaption (hwnd, szTitleName) ;
               bNeedSave = FALSE ;
               return 0 ;
               
          case IDM_FILE_OPEN:
               if (bNeedSave && IDCANCEL == AskAboutSave (hwnd, szTitleName))
                    return 0 ;
               if (PopFileOpenDlg (hwnd, szFileName, szTitleName))
               {
                    if (!PopFileRead (hwndEdit, szFileName))
                    {
                         OkMessage (hwnd, TEXT ("Could not read file %s!"),
                                    szTitleName) ;
                         szFileName[0]  = '\0' ;
                         szTitleName[0] = '\0' ;
                    }
               }
               
               DoCaption (hwnd, szTitleName) ;
               bNeedSave = FALSE ;
               return 0 ;
               
          case IDM_FILE_SAVE:
               if (szFileName[0])
               {
                    if (PopFileWrite (hwndEdit, szFileName))
                    {
                         bNeedSave = FALSE ;
                         return 1 ;
                    }
                    else
                    {
                         OkMessage (hwnd, TEXT ("Could not write file %s"),
                                    szTitleName) ;
                         return 0 ;
                    }
               }
                                   // fall through
          case IDM_FILE_SAVE_AS:
               if (PopFileSaveDlg (hwnd, szFileName, szTitleName))
               {
                    DoCaption (hwnd, szTitleName) ;
                    
                    if (PopFileWrite (hwndEdit, szFileName))
                    {
                         bNeedSave = FALSE ;
                         return 1 ;
                    }
                    else
                    {
                         OkMessage (hwnd, TEXT ("Could not write file %s"),
                                    szTitleName) ;                         return 0 ;
                    }
               }
               return 0 ;          case IDM_FILE_PRINT:
               if (!PopPrntPrintFile (hInst, hwnd, hwndEdit, szTitleName))
                    OkMessage (hwnd, TEXT ("Could not print file %s"),
                                     szTitleName) ;
               return 0 ;
               
          case IDM_APP_EXIT:
               SendMessage (hwnd, WM_CLOSE, 0, 0) ;
               return 0 ;
               
                    // Messages from Edit menu
               
          case IDM_EDIT_UNDO:
               SendMessage (hwndEdit, WM_UNDO, 0, 0) ;
               return 0 ;
               
          case IDM_EDIT_CUT:
               SendMessage (hwndEdit, WM_CUT, 0, 0) ;
               return 0 ;
               
          case IDM_EDIT_COPY:
               SendMessage (hwndEdit, WM_COPY, 0, 0) ;
               return 0 ;
               
          case IDM_EDIT_PASTE:
               SendMessage (hwndEdit, WM_PASTE, 0, 0) ;
               return 0 ;
               
          case IDM_EDIT_CLEAR:
               SendMessage (hwndEdit, WM_CLEAR, 0, 0) ;
               return 0 ;
               
          case IDM_EDIT_SELECT_ALL:
               SendMessage (hwndEdit, EM_SETSEL, 0, -1) ;
               return 0 ;
               
                    // Messages from Search menu
          case IDM_SEARCH_FIND:
               SendMessage (hwndEdit, EM_GETSEL, 0, (LPARAM) &iOffset) ;
               hDlgModeless = PopFindFindDlg (hwnd) ;
               return 0 ;
               
          case IDM_SEARCH_NEXT:
               SendMessage (hwndEdit, EM_GETSEL, 0, (LPARAM) &iOffset) ;
               
               if (PopFindValidFind ())
                    PopFindNextText (hwndEdit, &iOffset) ;
               else
                    hDlgModeless = PopFindFindDlg (hwnd) ;
               
               return 0 ;
               
          case IDM_SEARCH_REPLACE:
               SendMessage (hwndEdit, EM_GETSEL, 0, (LPARAM) &iOffset) ;
               hDlgModeless = PopFindReplaceDlg (hwnd) ;
               return 0 ;
               
          case IDM_FORMAT_FONT:
               if (PopFontChooseFont (hwnd))
                    PopFontSetFont (hwndEdit) ;
               
               return 0 ;
               
                    // Messages from Help menu
               
          case IDM_HELP:
               OkMessage (hwnd, TEXT ("Help not yet implemented!"), 
                                TEXT ("\0")) ;
               return 0 ;
               
          case IDM_APP_ABOUT:
               DialogBox (hInst, TEXT ("AboutBox"), hwnd, AboutDlgProc) ;
               return 0 ;
          }
          break ;
为啥返回值是1，又可是0？
1，0各代表啥意思？

Answer 1

是根据Windows消息传递机制所要求的，返回1说明你的程序对该command消息完成处理，消息不再往下传递；返回0是command消息需要继续往下传递

Answer 2

读下：          case IDM_FILE_SAVE_AS:
               if (PopFileSaveDlg (hwnd, szFileName, szTitleName))
               {
                    DoCaption (hwnd, szTitleName) ;
                    
                    if (PopFileWrite (hwndEdit, szFileName))
                    {
                         bNeedSave = FALSE ;
                         return 1 ;
                    }
                    else
                    {
                         OkMessage (hwnd, TEXT ("Could not write file %s"),
                                    szTitleName) ;                         return 0 ;
                    }
               }
               return 0 ;这段，我想你能理解。

Answer 3

to pcman
windows 消息傳遞機制能否說的詳細點
"消息往下傳遞"指望哪兒傳遞?

Answer 4

在 SDK 里 WM_COMMAND　的返回值被作为 SendMessage 的返回值或者抛弃，Windows 几乎不会处理这个返回值。MFC 里 WM_COMMAND 的返回值比较重要，MFC 根据返回值是否为 TRUE 判断消息是否被该对象处理了，如果否，则将消息发给 response-chain 的下一个 CmdTarget 对象处理