CustomDrawn listbox in a OwnerDrawn combobox

Hi,

I'm having a hard time understanding how to use a custom-drawn listbox in place of the native combobox listbox. You can read the whole source code below, made as short as possible (no asserts, dummy values). The first part implements a custom-drawn CListViewCtrl, with only one overriden method: OnPrePaint(). The second part implements an owner-drawn CComboBox, based on the "Tree Combo" source code from "Various ComboBox controls" article by Bjarke Viksoe (http://www.viksoe.dk/code/combos.htm). When the native combobox list is about to be displayed, OnDropDown() should prevent it from being used and display the custom-drawn list instead. And there comes my problem: the custom-drawn list method OnPrePaint() is never called so the custom-drawn listbox is never displayed. Instead, a normal lis
 tbox is used by the frawework as usual. Sure I have misunderstood something, but what ?...

Any help would be greatly appreciated !
Best regards.
Jean-Yves Chasle


---------- SOURCE CODE -----------
// Custom drawn listbox control
template< class T, class TBase = CListViewCtrl, class TWinTraits = CControlWinTraits >
class ATL_NO_VTABLE MyListBoxImpl
:   public CWindowImpl< T, TBase, TWinTraits >,
    public CCustomDraw< T >
{
public:
    typedef MyListBoxImpl< T, TBase, TWinTraits > TThisClass;

public:
    DECLARE_WND_SUPERCLASS( NULL, TBase::GetWndClassName() )

    // Never called when the control is part of the combobox...
    DWORD OnPrePaint( int /*iIdCtrl*/, LPNMCUSTOMDRAW poNMCD ) {
        return CDRF_SKIPDEFAULT;
    }

private:
    BEGIN_MSG_MAP( TThisClass )
        CHAIN_MSG_MAP_ALT( CCustomDraw< T >, 1 )
        MESSAGE_HANDLER( WM_CREATE, OnCreate )
    END_MSG_MAP()

    LRESULT OnCreate( UINT uiMsg, WPARAM wParam, LPARAM lParam, BOOL& /*bHandled*/ ) {
        LRESULT lRes = DefWindowProc( uiMsg, wParam, lParam );
        ModifyStyle( 0, (LVS_SINGLESEL | LVS_SHOWSELALWAYS) );
        return lRes;
    }
};

class MyListBox: public MyListBoxImpl< MyListBox > {
public:
    DECLARE_WND_SUPERCLASS( _T( "MyListBox" ), GetWndClassName() )
};


// Owner drawn combobox
template< class T, class TBase = CComboBox, class TWinTraits = CControlWinTraits >
class ATL_NO_VTABLE MyComboBoxImpl: public CWindowImpl< T, TBase, TWinTraits >
{
public:
    typedef MyComboBoxImpl< T, TBase, TWinTraits > TThisClass;

private:
    // Works fine with CListViewCtrl, not with MyListBox (which behaves like CListViewCtrl).
    CContainedWindowT< MyListBox > m_wndListbox;

public:
    DECLARE_WND_SUPERCLASS( NULL, TBase::GetWndClassName() )

    int InsertString( int nIndex, LPCTSTR szString ) {
        return m_wndListbox.InsertItem( nIndex, szString );
	}

private:
    BEGIN_MSG_MAP( TThisClass )
        MESSAGE_HANDLER( WM_CREATE, OnCreate )
        MESSAGE_HANDLER( WM_DESTROY, OnDestroy )
        MESSAGE_HANDLER( OCM_DRAWITEM, OnDrawItem )
        REFLECTED_COMMAND_CODE_HANDLER( CBN_DROPDOWN, OnDropDown )
        MESSAGE_HANDLER( WM_APP + 1, OnListHandleInput )
    ALT_MSG_MAP( 1 )
        MESSAGE_HANDLER( WM_LBUTTONDOWN, OnListButtonUp )
        MESSAGE_HANDLER( WM_KILLFOCUS, OnListKillFocus )
    END_MSG_MAP()

    LRESULT OnCreate( UINT /*uiMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL &/*rbHandled*/ ) {      
        LRESULT lRes = DefWindowProc();
        ModifyStyle( 0, (CBS_DROPDOWNLIST | CBS_OWNERDRAWFIXED | CBS_HASSTRINGS) );
        m_wndListbox.Create( this, 1, NULL, &rcDefault, NULL, (WS_POPUP | WS_BORDER | WS_CLIPSIBLINGS | WS_CLIPCHILDREN | LVS_SINGLESEL | LVS_SHOWSELALWAYS), 0 );
        return lRes;
    }
    LRESULT OnDestroy( UINT /*uiMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL &rbHandled ) {
        m_wndListbox.DestroyWindow();
        rbHandled = FALSE;
        return 0;
    }
    LRESULT OnDrawItem( UINT /*uiMsg*/, WPARAM /*wParam*/, LPARAM lParam, BOOL &/*rbHandled*/ ) {
        return TRUE;
    }
    LRESULT OnDropDown( WORD /*wNotifyCode*/, WORD /*wID*/, HWND /*hWndCtl*/, BOOL &rbHandled ) {
        PostMessage( WM_APP + 1 ); // Calls OnListHandleInput().
        rbHandled = FALSE;
        return 0;
    }
    LRESULT OnListHandleInput( UINT /*uiMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL &/*rbHandled*/ ) {
        ReleaseCapture(); // (Original comment by Bjarke Viksoe:) Force list to close prematurely!

        // Set our list control rect from the native combobox list rect.
        COMBOBOXINFO oCBInfo;
        oCBInfo.cbSize = sizeof( oCBInfo );
        GetComboBoxInfo( &oCBInfo );
        RECT rcList;
        ::GetWindowRect( oCBInfo.hwndList, &rcList );
        rcList.bottom = rcList.top + 100; //-- Dummy value

        // Make our list control show in place of the native combobox list.
        ::ShowWindow( oCBInfo.hwndList, SW_HIDE );
        m_wndListbox.SetWindowPos( HWND_TOP, &rcList, SWP_SHOWWINDOW );
        m_wndListbox.SetFocus();
        return 0;
    }
    LRESULT OnListButtonUp( UINT /*uiMsg*/, WPARAM /*wParam*/, LPARAM lParam, BOOL &/*rbHandled*/ ) {
        LRESULT lRes = m_wndListbox.DefWindowProc();
        SetFocus(); // Calls OnListKillFocus().
        return lRes;
    }
    LRESULT OnListKillFocus( UINT /*uiMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL &rbHandled ) {
        m_wndListbox.ShowWindow( SW_HIDE );
        rbHandled = FALSE;
        return 0;
    }
};

class MyComboBox: public MyComboBoxImpl< MyComboBox > {
public:
    DECLARE_WND_SUPERCLASS( _T( "MyComboBox" ), GetWndClassName() )
};


---------- Excerpt from CMainDlg::OnInitDialog() -----------
MyComboBox m_wndCombobox.Create( m_hWnd, CRect( CPoint( 400, 0 ), CSize( 100, 20 ) ), NULL, (WS_VISIBLE | WS_CHILD | WS_TABSTOP | WS_GROUP | CBS_DROPDOWNLIST | CBS_HASSTRINGS) );
// Use m_wndCombobox.InsertString() to populate it.




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