An MFC extension library to enable DLL plug-in technology for your application using MESSAGE_MAPs

// (c) R.I.Allen 2002
// You may use this code in anyway that you feel, no guarantees or waranties are implied
// please keep all headers with any source used.
//
// PIScrollView.cpp : implementation file
//

#include "stdafx.h"
#include "PlugInApp.h"
#include "PIScrollView.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CPIScrollView

IMPLEMENT_DYNCREATE(CPIScrollView, CScrollView)

CPIScrollView::CPIScrollView()
{
	m_pMaps = NULL;
	m_MapCount = 0;
}

CPIScrollView::~CPIScrollView()
{
	// release message map pointers
	for (int i = 0; i < m_MapCount; ++i)
	{
		delete m_pMaps[i];
		m_pMaps[i] = NULL;
	}
	delete []m_pMaps;
	m_pMaps = NULL;
	m_state.SetDestroyed();
}

void CPIScrollView::InitialisePlugIns()
{
	CPlugInApp *pApp = static_cast<CPlugInApp*>(AfxGetApp());
	// get our pointers to any plug in maps
	m_pMaps = pApp->GetMessageMaps(this, m_MapCount);
}

BEGIN_MESSAGE_MAP(CPIScrollView, CScrollView)
	//{{AFX_MSG_MAP(CPIScrollView)
		// NOTE - the ClassWizard will add and remove mapping macros here.
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CPIScrollView drawing

void CPIScrollView::OnDraw(CDC* pDC)
{
	UNUSED_PARAMETER(pDC);
}

/////////////////////////////////////////////////////////////////////////////
// CPIScrollView diagnostics

#ifdef _DEBUG
void CPIScrollView::AssertValid() const
{
	CScrollView::AssertValid();
}

void CPIScrollView::Dump(CDumpContext& dc) const
{
	CScrollView::Dump(dc);
}
#endif //_DEBUG

/////////////////////////////////////////////////////////////////////////////
// CPIScrollView message handlers
BOOL CPIScrollView::OnCmdMsg(UINT nID, int nCode, void* pExtra, AFX_CMDHANDLERINFO* pHandlerInfo) 
{
	// check to see whether any of the plug-in DLL's
	// want to intercept this message and process it before the application class
	CPlugInApp *pApp = static_cast<CPlugInApp*>(AfxGetApp());
	CPIState	stateCopy(m_state);

	ASSERT(pApp);
	BOOL ret_pre = FALSE;
	BOOL ret_app = FALSE;
	BOOL ret_post = FALSE;
	m_bSuppressThisMessage = false;
	
	// allow DLL's to process this message before the exe
	ret_pre = pApp->ProcessCommandMessageMaps(stateCopy, true, &m_bSuppressThisMessage, m_pMaps, m_MapCount, nID, nCode, pExtra, pHandlerInfo);
	if (!m_bSuppressThisMessage)
		{
		// allow the exe to process the message is it hasn't been suppressed by a DLL
		ret_app = CScrollView::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo);
		}
	// allow DLL to process the message after the exe
	// note that DLLs get to do this whether the message has been supressed or not
	if (!stateCopy.IsDestroyed())
	{
		ret_post = pApp->ProcessCommandMessageMaps(stateCopy, false, &m_bSuppressThisMessage, m_pMaps, m_MapCount, nID, nCode, pExtra, pHandlerInfo);
	}

	if (ret_pre || ret_app || ret_post)
		return  TRUE;
	return FALSE;
}

BOOL CPIScrollView::OnWndMsg(UINT message, WPARAM wParam, LPARAM lParam, LRESULT* pResult)
{
	LRESULT	lResult;
	// special case for commands
	if (message == WM_COMMAND)
		{
		if (OnCommand(wParam, lParam))
			{
			lResult = 1;
			if (pResult != NULL)
				*pResult = lResult;
			return TRUE;
			}
		return FALSE;
		}

	// special case for notifies
	if (message == WM_NOTIFY)
		{
		NMHDR* pNMHDR = (NMHDR*)lParam;
		if (pNMHDR->hwndFrom != NULL && OnNotify(wParam, lParam, &lResult))
			{
			if (pResult != NULL)
				*pResult = lResult;
			return TRUE;
			}
		return FALSE;
		}

	// check to see whether any of the plug-in DLL's
	// want to intercept this message and process it before the application class
	CPlugInApp *pApp = static_cast<CPlugInApp*>(AfxGetApp());
	ASSERT(pApp);
	CPIState	stateCopy(m_state);
	BOOL ret_pre = FALSE;
	BOOL ret_app = FALSE;
	BOOL ret_post = FALSE;
	m_bSuppressThisMessage = false;
	// allow DLL's to process this message before the exe
	ret_pre = pApp->ProcessWindowMessageMaps(stateCopy, true, &m_bSuppressThisMessage, m_pMaps, m_MapCount, message, wParam, lParam, pResult);
	if (!m_bSuppressThisMessage)
		{
		// allow the exe to process the message is it hasn't been suppressed by a DLL
		ret_app = CScrollView::OnWndMsg(message, wParam, lParam, pResult);
		}
	if (!stateCopy.IsDestroyed())
	{
		// allow DLL to process the message after the exe
		// note that DLLs get to do this whether the message has been supressed or not
		ret_pre = pApp->ProcessWindowMessageMaps(stateCopy, false, &m_bSuppressThisMessage, m_pMaps, m_MapCount, message, wParam, lParam, pResult);
	}

	if (ret_pre || ret_app || ret_post)
		return  TRUE;
	return FALSE;
}