Message Map in Win32 No-MFC

Question

How could I create similar structure to handle Win32 Messages like it is in MFC?

In MFC;

BEGIN_MESSAGE_MAP(CSkinCtrlTestDlg, CDialog)
    //{{AFX_MSG_MAP(CSkinCtrlTestDlg)
    ON_BN_CLICKED(IDC_BROWSE, OnBrowse)
    ON_BN_CLICKED(IDC_DEFAULTSKIN, OnChangeSkin)
    ON_WM_DRAWITEM()
    ON_WM_MEASUREITEM()
    ON_WM_COMPAREITEM()
    ON_BN_CLICKED(IDC_CHECK3, OnCheck3)
    //}}AFX_MSG_MAP
END_MESSAGE_MAP()

BEGIN_MESSAGE_MAP macro handles this behaviour. What to do for pure Win32?

Answer 1

Here is a breif summary of the code I use to do this in the Zeus programmer's editor:

Step 1: Define a couple of message structure to hold the Windows message details:

typedef struct
{
  MSG     msg;
  LRESULT lResult;
} xMessage;

struct xWM_COMMAND
{
  HWND hwnd;
  UINT Msg;
  WORD ItemID;
  WORD NotifyCode;
  HWND Ctl;
  LRESULT lResult;
};

//-- unpack a message buffer
#define MSG_UNPACK(var, id, msg) x##id *var = (x##id *)(msg);

Step 2: Define a base window class with a few special methods:

class xWindow
{
protected:
  //-- windows callback function
  static LRESULT CALLBACK wndProc(HWND hwnd, UINT msg, 
                                  WPARAM wParam, 
                                  LPARAM lParam);

  //-- a message dispatch method
  void dispatch(HWND hwnd, UINT uMessageID, WPARAM wParam, 
                LPARAM lParam, LRESULT &Result);

  //-- method for command message dispatching
  virtual void dispatchToCmdMap(xMessage *pMessage);

  //-- method for windows message dispatching
  virtual void dispatchToMsgMap(xMessage *pMessage);
};

Step 3: Define a few macros to do the dispatching of the Windows messages:

#define BEGIN_MSG_MAP                          \
   protected:                                  \
   virtual void dispatchToMsgMap(xMessage *msg)\
   {                                           \
     if (msg->msg.message == WM_NULL)          \
     {                                         \
       return;                                 \
     }

#define MSG_HANDLER(meth, wm_msg)              \
     else if (msg->msg.message == wm_msg)      \
     {                                         \
       this->meth(msg);                        \
       return;                                 \
     }

#define END_MSG_MAP(base)                      \
     else if (msg->msg.message == WM_COMMAND)  \
     {                                         \                       
       this->dispatchToCmdMap(msg);            \                       
       return;                                 \                       
     }                                         \                       
     else if (msg->msg.message == WM_NOTIFY)   \                       
     {                                         \                       
       this->dispatchToNotifyMap(msg);         \                       
       return;                                 \                       
     }                                         \                       
                                               \                       
     base::dispatchToMsgMap(msg);              \                       
   };

#define BEGIN_CMD_MAP                          \
   virtual void dispatchToCmdMap(xMessage *msg)\
   {                                           \                              
     MSG_UNPACK(Cmd, WM_COMMAND, msg);         \                              
                                               \                              
     if (Cmd->ItemID == 0)                     \                              
     {                                         \                              
        /* not allowed */                      \                              
     }                                                                        

#define CMD_HANDLER(meth, cmd_id)              \
     else if (Cmd->ItemID == cmd_id)           \
     {                                         \                                
       this->meth(Cmd->ItemID);                \                                
     }                                                                          

#define END_CMD_MAP(base)                      \
     else                                      \                              
     {                                         \                              
       base::dispatchToCmdMap(msg);        \                              
     }                                         \                              
   };

Step 4: Define the dispatcher method:

void xWindow::dispatch(HWND, UINT uMessageID, WPARAM wParam, 
                       LPARAM lParam, LRESULT &Result)
{
  xMessage message;

  //-- build up a message packet
  message.msg.message = uMessageID;
  message.msg.wParam  = wParam;
  message.msg.lParam  = lParam;
  message.lResult     = 0;

  //-- dispatch the message
  this->dispatchToMsgMap(&message);
}

Step 5: Define the static window procedure method (NOTE: this method will need to be used as the Window procedure of the window class when the class is first registered):

LRESULT CALLBACK xWindow::wndProc(HWND hwnd, UINT msg, 
                                  WPARAM wParam, 
                                  LPARAM lParam)
{
  LRESULT lResult = 0;

  //-- look for the creation message
  if (msg == WM_NCCREATE)
  {
    CREATESTRUCT *pCreateData = (CREATESTRUCT*)lParam;

    //-- get the window object passed in
    xWindow *pWindow = (xWindow)pCreateData->lpCreateParams;

    if (pWindow)
    {
      //-- attach the window object to the hwnd
      SetWindowLong(hwnd, pWindow);

      //-- let the window object dispatch the message
      pWindow->dispatch(hwnd, msg, wParam, lParam, lResult);
    }
    else
    {
      //-- leave the message to windows
      lResult = DefWindowProc(hwnd, msg, wParam, lParam);
    }
  }
  else if (hwnd)
  {
    //-- get the object attached to the hwnd
    xWindow *pWindow = (xWindow *)GetWindowLong(hwnd);

    //-- check to see if we have an object window attached to the handle
    if (pWindow)
    {
      //-- let the window object dispatch the message
      pWindow->dispatch(hwnd, msg, wParam, lParam, lResult);
    }
    else
    {
      //-- leave the message to windows
      lResult = ::DefWindowProc(hwnd, msg, wParam, lParam);
    }
  }

  return lResult;
}

Now, using this base class it is possible to define a new window class that will look like this:

class MyWindow : public xWindow
{
protected:  
  //-- the WM_COMMAND message handlers
  virtual void onAdd(int);
  virtual void onDelete(int);

  //-- the WM_CLOSE message handler
  virtual void onClose(xMessage *pMessage);

  //-- the WM_SIZE message handler
  virtual void onSize(xMessage *pMessage);

public:
  //-- ctor and dtor
  MyWindow();
  virtual ~MyWindow();

  BEGIN_MSG_MAP
    //-- command message handlers
    CMD_HANDLER(onAdd   , IDPB_ADD   )
    CMD_HANDLER(onDelete, IDPB_DELETE)

    //-- other message handling
    MSG_HANDLER(onClose , WM_CLOSE)
    MSG_HANDLER(onSize  , WM_SIZE )
  END_MSG_MAP(xWindow)
};

Edit: How this code works.

The secret to understanding how this code works is to remember the wndProc in the xWindow class is nothing but a Win32 Window procedure passed to RegisterClassEx when the Win32 Window is registered.

Now if you look at the wndProc code you will see it does a bit of setting up and checking but generally it does nothing more than send the Windows message to the dispatch method.

The dispatch method is even simpler as it does nothing more than pack the Windows message into an easy to move structure and then sends it off to the dispatchToMsgMap method.

Now look at the MyWindow class an you will see this code:

BEGIN_MSG_MAP    
   //-- command message handlers    
   CMD_HANDLER(onAdd   , IDPB_ADD   )    
   CMD_HANDLER(onDelete, IDPB_DELETE)    

   //-- other message handling    
   MSG_HANDLER(onClose , WM_CLOSE)    
   MSG_HANDLER(onSize  , WM_SIZE )  
END_MSG_MAP(xWindow)

This code is just using the macros defined earlier. If you take a close look at these macros you will see the code above is in fact creating a dispatchToMsgMap method. This is the exact same dispatchToMsgMap method that was called by the dispatch method.

I know this method of handling Windows messages does work as I use this exact same approach in the Zeus for Windows editor.