Making of a Color Spy utility with WTL

//////////////////////////////////////////////////////////////////////
// ColorSpy Copyright 2003 Tom Furuya [tom_furuya@yahoo.com]
//
// Readers of this article may copy the code for use in developing their own applications.
// If the code is used in a commercial application, however, an acknolegement must 
// be included in the following form: 
// "Segment of the code (c) 2003 Tom Furuya for CodeProject.com".
//
//////////////////////////////////////////////////////////////////////

#if !defined(AFX_COLORSPYCBVIEWER_H__BAB47C31_C2AC_4725_B0E4_A45F62CF3E83__INCLUDED_)
#define AFX_COLORSPYCBVIEWER_H__BAB47C31_C2AC_4725_B0E4_A45F62CF3E83__INCLUDED_

#pragma once

//////////////////////////////////////////////////////////////////////
// CColorSpy's Clipboard Viewer 
// 
// CColorSpyCBViewer is a class that turns ColorSpy into a clipboard viewer window 
// for reading color codes from clipboard.
//
////////////////////////////////////////////////////////////////////////
template<typename T> 
class CColorSpyCBViewer
{
public:
    HWND m_hWndNextCBViewer;
    bool m_bRegistered;
    
    BEGIN_MSG_MAP(CColorSpyCBViewer< T >)
        ALT_MSG_MAP(1)
        MESSAGE_HANDLER(WM_CREATE, OnCreate)       // for CWindowImpl based windows
        MESSAGE_HANDLER(WM_INITDIALOG, OnCreate)   // for CDialogImpl based windows
        MESSAGE_HANDLER(WM_DESTROY, OnDestroy)
        // Notification handlers
        MESSAGE_HANDLER(WM_DRAWCLIPBOARD, OnDrawClipboard)
        MESSAGE_HANDLER(WM_CHANGECBCHAIN, OnChangeCbChain) // necessary indeed
    END_MSG_MAP()
        
    CColorSpyCBViewer() : m_hWndNextCBViewer(0), m_bRegistered(false) {}

    LRESULT OnCreate(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)
    {
        bHandled = FALSE;
        T* pT = static_cast<T*>(this);

        // Join the members of clipboard viewer chain
        m_hWndNextCBViewer = pT->SetClipboardViewer(); //can be nothing
        m_bRegistered = true;
        return 0;
    }
    
    LRESULT OnDestroy(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)
    {
        T* pT = static_cast<T*>(this);

        // Say good-bye to my friends
        if (IsWindow(m_hWndNextCBViewer))
            pT->ChangeClipboardChain(m_hWndNextCBViewer);
        return 0;
    }
    
    LRESULT OnDrawClipboard(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& /*bHandled*/)
    {
        // Viewer receives whenever the content of the clipboard is changed
        // wParam is a handle to the window that has put clipboard data
        
        T* pT = static_cast<T*>(this);
        
        // Registering this window as a CB wiewer window
        if (m_bRegistered == false) // calling ::SetClipboardViewer() in OnCrate handler
        {
            ATLTRACE("Registering... wParam: %#x\n", wParam);
            return 0; // do nothing but return gracefully
        }

        ATLTRACE("OnDrawClipboard(): Wnd %#x put CB data\n", wParam);

        if (IsClipboardFormatAvailable(CF_TEXT) && pT->OpenClipboard())
        {
            CString text;
            HANDLE hData = ::GetClipboardData( CF_TEXT );
            text = (char*)::GlobalLock( hData );
            ::GlobalUnlock( hData );
            CloseClipboard();

            pT->SetColor(text);
        }
        
        // Pass WM_DRAWCLIPBOARD to the next window in clipboard viewer chain
        RouteMessage(uMsg, wParam, lParam);
        return 0;
    }
    
    LRESULT OnChangeCbChain(UINT /*uMsg*/, WPARAM wParam, LPARAM lParam, BOOL& /*bHandled*/)
    {
        T* pT = static_cast<T*>(this);

        // Clipboard wiewer window is supposed to respond to WM_CHANGECBCHAIN.

        HWND hWndRemove = reinterpret_cast<HWND>(wParam);
        HWND hWndAfter = reinterpret_cast<HWND>(lParam);
        
        if (m_hWndNextCBViewer == hWndRemove)
        {
            m_hWndNextCBViewer = hWndAfter;
        }
        
        // pass the WM_CHANGECBCHAIN (0x030D)
        RouteMessage(WM_CHANGECBCHAIN, wParam, lParam);
        return 0;
    }

    void RouteMessage(UINT uMsg, WPARAM wParam, LPARAM lParam)
    {
        // Toss WM_CHANGECBCHAIN message to the next Clipboard wiewer in the viewer chain
        // to notify of the update of chain.
        if (m_hWndNextCBViewer)
            ::SendMessage(m_hWndNextCBViewer, uMsg, wParam, lParam);
    }
};


#endif // !defined(AFX_COLORSPYCBVIEWER_H__BAB47C31_C2AC_4725_B0E4_A45F62CF3E83__INCLUDED_)