CMessageMap

class CMessageMap

CMessageMap is an abstract base class that allows an object's message maps to be accessed by another object. In order for an object to expose its message maps, its class must derive from CMessageMap.

ATL uses CMessageMap to support contained windows and dynamic message map chaining. For example, any class containing a CContainedWindow object must derive from CMessageMap. The following code is taken from the SUBEDIT sample. Through CComControl, the CAtlEdit class automatically derives from CMessageMap.

class CAtlEdit : public CComControl<CAtlEdit>, ...
                 // CComControl derives from CWindowImpl,
                 // which derives from CMessageMap
{
public:
   // Declare a contained window data member
   CContainedWindow m_EditCtrl;
   // Initialize the contained window:
   // 1. Pass "EDIT" to specify that the contained 
   // window should be based on the standard 
   // Windows Edit box
   // 2. Pass 'this' pointer to specify that CAtlEdit 
   // contains the message map to be used for the 
   // contained window's message processing
   // 3. Pass the identifier of the message map. In
   // this case, '1' identifies the message map
   // declared with ALT_MSG_MAP(1)
   CAtlEdit() : m_EditCtrl(_T("EDIT"), this, 1)
   {
      m_bWindowOnly = TRUE;
   }
   // Declare the default message map
   BEGIN_MSG_MAP(CAtlEdit)
      MESSAGE_HANDLER(WM_PAINT, OnPaint)
      ...
   // Declare an alternate message map,
   // identified by '1'
   ALT_MSG_MAP(1)
      MESSAGE_HANDLER(WM_CHAR, OnChar)
   END_MSG_MAP()
   ...
};

Because the contained window, m_EditCtrl, will use a message map in the containing class, CAtlEdit derives from CMessageMap.

For more information about message maps, see Message Maps in the article “ATL Window Classes.”

#include <atlwin.h>

See Also CDynamicChain, BEGIN_MSG_MAP, ALT_MSG_MAP


CMessageMap Class Members

Methods
ProcessWindowMessageAccesses a message map in the CMessageMap-derived class.

CMessageMap Overview


Methods


CMessageMap::ProcessWindowMessage

virtual BOOL ProcessWindowMessage( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT& lResult, DWORD dwMsgMapID ) = 0;

Return Value

TRUE if the message is fully handled; otherwise, FALSE.

Parameters

hWnd [in] The handle to the window receiving the message.

uMsg [in] The message sent to the window.

wParam [in] Additional message-specific information.

lParam [in] Additional message-specific information.

lResult [out] The result of the message processing.

dwMsgMapID [in] The identifier of the message map that will process the message. The default message map, declared with BEGIN_MSG_MAP, is identified by 0. An alternate message map, declared with ALT_MSG_MAP(msgMapID), is identified by msgMapID.

Remarks

Accesses the message map identified by dwMsgMapID in a CMessageMap-derived class. Called by the window procedure of a CContainedWindow object or of an object that is dynamically chaining to the message map.

CMessageMap Overview | Class Members

See Also CHAIN_MSG_MAP_DYNAMIC, CHAIN_MSG_MAP_ALT_DYNAMIC