WM_INPUTLANGCHANGE message

// Subclass used to capture messages from the ComboBox Edit control
// allowing the current charset to be changed when WM_INPUTLANGCHANGE
// is received.
class AFX_EXT_CLASS CMyComboEditBox : public CEdit
{
    DECLARE_DYNAMIC(CMyComboEditBox)

public:
    CMyComboEditBox();
    virtual ~CMyComboEditBox();

protected:
    afx_msg LRESULT OnInputLangChange(WPARAM wParam, LPARAM lParam);

    DECLARE_MESSAGE_MAP()

protected:
    CFont* m_pFont;
};

class AFX_EXT_CLASS CMyComboBox : public CComboBox
{
public:
    CMyComboBox();
    virtual ~CMyComboBox();

    DECLARE_DYNAMIC(CMyComboBox)
// ...
    // Override Create so we can subclass the Edit portion of the control
    BOOL Create(DWORD dwStyle, const RECT &rect, CWnd* pParentWnd, UINT nID);

protected:
    CLBComboEditBox m_edit;
// ...

afx_msg LRESULT OnInputLangChange(WPARAM wParam, LPARAM lParam);

    DECLARE_MESSAGE_MAP()
};

In MyComboBox.cpp

///////////////////////////////////////////////////////////////////////
//
// CMyComboBox - implementation

CMyComboBox::CMyComboBox()
{
}

CMyComboBox::~CMyComboBox()
{
    // Stop subclassing
    if (NULL != m_edit.GetSafeHwnd())
        m_edit.UnsubclassWindow();
}

IMPLEMENT_DYNAMIC(CMyComboBox, CComboBox)

BEGIN_MESSAGE_MAP(CMyComboBox, CComboBox)
    ON_MESSAGE(WM_INPUTLANGCHANGE, OnInputLangChange)
END_MESSAGE_MAP()

// Override Create so we can subclass the Edit control
BOOL CMyComboBox::Create(DWORD dwStyle, const RECT &rect, CWnd* pParentWnd, UINT nID)
{
    BOOL fCreated = __super::Create(dwStyle, rect, pParentWnd, nID);
    if (fCreated && m_edit.GetSafeHwnd() == NULL)
    {
        // Note: to use COMBOBOXINFO the following defines must be set in stdafx.h (ie. XP and higher)
        // #define WINVER 0x0500
        // #define _WIN32_WINNT 0x0501
        // #define _WIN32_WINDOWS 0x0500
        // #define _WIN32_IE 0x0501

        COMBOBOXINFO info = { sizeof(COMBOBOXINFO) };
        if (GetComboBoxInfo(&info))
            m_edit.SubclassWindow(info.hwndItem);
    }
    return fCreated;
}

LRESULT CMyComboBox::OnInputLangChange(WPARAM wParam, LPARAM lParam)
{
    // Forward the message to the combo's editbox
    return m_edit.SendMessage(WM_INPUTLANGCHANGE, wParam, lParam);

    // Alternatively send up to the parent to handle
    // return GetParent()->SendMessage(WM_INPUTLANGCHANGE, wParam, lParam);
}


///////////////////////////////////////////////////////////////////////
//
// CMyComboEditBox - implementation

IMPLEMENT_DYNAMIC(CMyComboEditBox, CEdit)

CMyComboEditBox::CMyComboEditBox() : m_pFont(NULL)
{
}

CMyComboEditBox::~CMyComboEditBox()
{
    if (m_pFont)
        delete m_pFont;
}

BEGIN_MESSAGE_MAP(CMyComboEditBox, CEdit)
    ON_MESSAGE(WM_INPUTLANGCHANGE, OnInputLangChange)
END_MESSAGE_MAP()

// CMyComboEditBox message handlers

LRESULT CMyComboEditBox::OnInputLangChange(WPARAM wParam, LPARAM lParam)
{
    UNUSED_ALWAYS(lParam);

    // Get the current font
    CFont* pEditFont = GetFont();

    // Obtain the font characteristics
    LOGFONT lf;
    pEditFont->GetLogFont(&lf);

    // Set the new charset (e.g. 161 for Greek)
    lf.lfCharSet = (BYTE)LOWORD(wParam);

    // Keep track of the old font (if any)
    CFont* pOldFont = m_pFont;

    // Create a new font based on the updated characteristics
    m_pFont = new CFont();
    m_pFont->CreateFontIndirect(&lf);
    SetFont(m_pFont);

    // Clean up the previous font (if any)
    if (pOldFont) delete pOldFont;

    return 0;
}

 WM_INPUTLANGCHANGE = &H51