Windows 編程[21] – WM_MENUSELECT 訊息與 GetMenuString 函數

提示:

1、功能表項目的標識存放在 WM_MENUSELECT 訊息的 lParam 參數中的低兩位.

2、WM_MENUSELECT 也包括系統功能表發送的訊息.

3、因為頂層菜單(File Edit Help)一般在資源檔中設同樣的標識符(譬如: 65535), 所以系統會把它們的位置(或者叫順序)當作標識; 因此執行 GetMenuString 時, 需要使用用非預設(非0)的 MF_BYPOSITION 參數.

4、因為系統功能表的標識都大於 $F000, 所以要求我們自訂的菜單標識一般要小於這個數; 在程式中我們也是根據這個道理來區別菜單來源的.

本例:

本例使用的資源檔(TestRes.rc):

#define IDM_New   101#define IDM_Open  102#define IDM_Save  103#define IDM_Exit  104#define IDM_Cut   201#define IDM_Copy  202#define IDM_Paste 203#define IDM_About 301MyMenu1 MENUEX DISCARDABLEBEGIN  POPUP "&File"        ,65535  BEGIN    MENUITEM "&New"    ,IDM_New    MENUITEM "&Open"   ,IDM_Open    MENUITEM "&Save"   ,IDM_Save    MENUITEM SEPARATOR    MENUITEM "E&xit"   ,IDM_Exit  END  POPUP "&Edit"        ,65535  BEGIN    MENUITEM "Cu&t"    ,IDM_Cut    MENUITEM "&Copy"   ,IDM_Copy    MENUITEM "&Paste"  ,IDM_Paste  END  POPUP "&Help"        ,65535  BEGIN    MENUITEM "&About"  ,IDM_About  ENDEND

本例代碼檔案:

program Project1;{$R 'TestRes.res' 'TestRes.rc'}uses  Windows, Messages;{收到 WM_MENUSELECT 訊息時需要做的工作}procedure OnMenuSelect(h: HWND; wParam: Integer);var  buf: array[0..255] of Char;  s: string;  w: Word;begin  w := LoWord(wParam);  Str(w, s);  case w of    0..99        : GetMenuString(GetMenu(h), w, buf, Length(buf), MF_BYPOSITION);    100..$F000   : GetMenuString(GetMenu(h), w, buf, Length(buf), MF_BYCOMMAND);    $F001..$FFFF : GetMenuString(GetSystemMenu(h, False), w, buf, Length(buf), MF_BYCOMMAND);  end;  s := s + ' - ' + buf;  SetWindowText(h, PChar(s));end;function WndProc(wnd: HWND; msg: UINT; wParam,lParam: Integer): Integer; stdcall;begin  Result := 0;  case msg of    WM_MENUSELECT : OnMenuSelect(wnd, wParam); {收到 WM_MENUSELECT 訊息後調用 OnMenuSelect 過程}    WM_DESTROY    : PostQuitMessage(0);  else    Result := DefWindowProc(wnd, msg, wParam, lParam);  end;end;function RegMyWndClass: Boolean;var  cls: TWndClass;begin  cls.style         := CS_HREDRAW or CS_VREDRAW;  cls.lpfnWndProc   := @WndProc;  cls.cbClsExtra    := 0;  cls.cbWndExtra    := 0;  cls.hInstance     := HInstance;  cls.hIcon         := 0;  cls.hCursor       := LoadCursor(0, IDC_ARROW);  cls.hbrBackground := HBRUSH(COLOR_WINDOW + 1);  cls.lpszMenuName  := 'MyMenu1';  cls.lpszClassName := 'MyWnd';  Result := RegisterClass(cls)  0;end;{程式入口}const  tit = 'New Form';  ws = WS_OVERLAPPEDWINDOW;  x = 100; y = 100; w = 300; h = 180;var  hWnd: THandle;  Msg : TMsg;begin  RegMyWndClass;  hWnd := CreateWindow('MyWnd', tit, ws, x, y, w, h, 0, 0, HInstance, nil);  ShowWindow(hWnd, SW_SHOWNORMAL);  UpdateWindow(hWnd);  while(GetMessage(Msg, 0, 0, 0)) do  begin    TranslateMessage(Msg);    DispatchMessage(Msg);  end;end.