CHAIN_MSG_MAP_MEMBER

Article
12/01/2015

Defines an entry in a message map.

Syntax

CHAIN_MSG_MAP_MEMBER( theChainMember )

Parameters

theChainMember
[in] The name of the data member containing the message map.

Remarks

CHAIN_MSG_MAP_MEMBER directs messages to a data member's default message map (declared with BEGIN_MSG_MAP). To direct messages to a data member's alternate message map (declared with ALT_MSG_MAP), use CHAIN_MSG_MAP_ALT_MEMBER.

Note

Always begin a message map with BEGIN_MSG_MAP. You can then declare subsequent alternate message maps with ALT_MSG_MAP. The END_MSG_MAP macro marks the end of the message map. Every message map must have exactly one instance of BEGIN_MSG_MAP and END_MSG_MAP.

For more information about using message maps in ATL, see Message Maps.

Example

class CMyContainerClass : public CWindowImpl<CMyContainerClass>
{
public:
   CMyContainedClass m_obj;

   BEGIN_MSG_MAP(CMyContainerClass)
      MESSAGE_HANDLER(WM_PAINT, OnPaint)
      // chain to default message map of m_obj
      CHAIN_MSG_MAP_MEMBER(m_obj)
   ALT_MSG_MAP(1)
      // chain to default message map of m_obj
      CHAIN_MSG_MAP_MEMBER(m_obj)
   ALT_MSG_MAP(2)
      MESSAGE_HANDLER(WM_CHAR, OnChar)
      // chain to alternate message map of m_obj
      CHAIN_MSG_MAP_ALT_MEMBER(m_obj, 1)
   END_MSG_MAP()

   LRESULT OnPaint(UINT /*nMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, 
      BOOL& /*bHandled*/)
   {
      return 0;   
   }
   LRESULT OnChar(UINT /*nMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, 
      BOOL& /*bHandled*/)
   {
      return 0;   
   }
};

This example illustrates the following:

If a window procedure is using CMyClass's default message map and OnPaint does not handle a message, the message is directed to m_obj's default message map for processing.
If a window procedure is using the first alternate message map in CMyClass, all messages are directed to m_obj's default message map.
If a window procedure is using CMyClass's second alternate message map and OnChar does not handle a message, the message is directed to the specified alternate message map of m_obj. Class CMyContainedClass must have declared this message map with ALT_MSG_MAP(1).

Requirements

Header: atlwin.h

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