MFC Extension library : Enhanced print preview plug-in

#include "stdafx.h"
#include "EnhancedPreview.h"
#include "MultiPagePreview.h"
#include "resource.h"

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

CEnhancedPrintPreview	plugIn(false);

IMPLEMENT_DYNCREATE(CEnhancedPrintPreview, CPlugInMap)

CEnhancedPrintPreview::CEnhancedPrintPreview()
{
}

CEnhancedPrintPreview::CEnhancedPrintPreview(bool special)
{
    UNREFERENCED_PARAMETER(special);
	AddObject();
}

CEnhancedPrintPreview::~CEnhancedPrintPreview()
{
	TRACE("CEnhancedPrintPreview::~CEnhancedPrintPreview()\n");
}

BEGIN_MESSAGE_MAP(CEnhancedPrintPreview, CPlugInMap)
	//{{AFX_MSG_MAP(CEnhancedPrintPreview)
	ON_COMMAND(ID_FILE_PRINT_PREVIEW, OnFilePrintPreview)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CEnhancedPrintPreview message handlers

bool CEnhancedPrintPreview::IsPlugInFor(CRuntimeClass *pClass)
{
	if (pClass->IsDerivedFrom(RUNTIME_CLASS(CView)))
	{
		// we are only a plug-in for any view class
		// as the view classes support the preview option
		return true;
	}
	return false;
}

CPlugInMap* CEnhancedPrintPreview::CreateMapObject()
{
	return new CEnhancedPrintPreview;
}

void CEnhancedPrintPreview::OnFilePrintPreview()
{
	if (IsPreCall())
	{
		// were replacing the standard MFC print preview and replacing it with
		// our enhanced version.

		SuppressThisMessage();
		// replace the default print preview with ours!

		// In derived classes, implement special window handling here
		// Be sure to Unhook Frame Window close if hooked.
		
		// must not create this on the frame.  Must outlive this function
		CPrintPreviewState* pState = new CPrintPreviewState;
		
		// DoPrintPreview's return value does not necessarily indicate that
		// Print preview succeeded or failed, but rather what actions are necessary
		// at this point.  If DoPrintPreview returns TRUE, it means that
		// OnEndPrintPreview will be (or has already been) called and the
		// pState structure will be/has been deleted.
		// If DoPrintPreview returns FALSE, it means that OnEndPrintPreview
		// WILL NOT be called and that cleanup, including deleting pState
		// must be done here.
		CView *pView = static_cast<CView*>(m_pPlugInFor);
		
		if (!pView->DoPrintPreview(IDD_PREVIEW, pView, RUNTIME_CLASS(CMultiPagePreviewView), pState))
		{
			// In derived classes, reverse special window handling here for
			// Preview failure case
			
			TRACE0("Error: DoPrintPreview failed.\n");
			AfxMessageBox(AFX_IDP_COMMAND_FAILURE);
			delete pState;      // preview failed to initialize, delete State now
			pState = NULL;
		}
	}
}