Question

due to layout customization needs, I extended CTreeCtrl class.

I absolutely need to use CDC::DrawText() function to dinamically (re)write the text of the single nodes, WITHOUT calling SetItemText() function more than once(mandatory requisite).

Then, I wrote my own implementation of OnPaint() method.
I implemented also a DrawItems() method which draws nodes in CTreeCtrl.

Since I don’t want to modify anything else than single labels beside the single nodes, then I need to re-implement most of original CTreeCtrl::OnPaint() code.

I only have two doubts:

1. How can I show the DEFAULT CTreeCtrl icons? I dont’need/don’t want
   custom icons.
2. How can I restore the default layout of selection mode for individual nodes?

Simply, currently selected nodes should be appear highlighted.

Some pieces of simplified, auto-explanatory code below:

void MyDlg::OnPaint()
{
    CPaintDC dc(this);
    CDC dc_ff;  
    CBitmap bm_ff;
    CBitmap *bm_old;
    CFont *font;
    CFont *old_font;
    CFont fontDC;
    int old_mode;
    GetClientRect(&m_Rect);

    dc_ff.CreateCompatibleDC( &dc );
    bm_ff.CreateCompatibleBitmap( &dc, m_Rect.Width(), m_Rect.Height() ); 
    dc_ff.SelectObject( &bm_ff ); 
    font = GetFont();
    old_font = dc_ff.SelectObject( font );

    // Could / Should be called here?
    CWnd::DefWindowProc(WM_PAINT, (WPARAM)dc.m_hDC, 0);

    old_mode = dc_ff.SetBkMode(TRANSPARENT);

    dc_ff.FillSolidRect(m_Rect, dc_ff.GetBkColor());

    DrawItems( &dc_ff ); // DrawItems() member function draws single nodes of CTreeCtrl

    dc.BitBlt( m_Rect.left, m_Rect.top, m_Rect.Width(), m_Rect.Height(), &dc_ff, 0, 0, SRCCOPY);

    dc_ff.SelectObject( old_font );
    dc_ff.SetBkMode( old_mode );
    dc_ff.SelectObject( bm_old ); 
}

void MyDlg::DrawItems( CDC *pDC )
{
    // draw items
    HTREEITEM show_item, parent;
    CRect rc_item;
    CString name;
    DWORD tree_style;
    int count = 0;
    int state;
    bool selected;
    bool has_children;

    show_item = GetFirstVisibleItem();
    if ( show_item == NULL )
        return;
    color = pDC->GetTextColor();
    tree_style = ::GetWindowLong( m_hWnd, GWL_STYLE ); 

    do
    {
        state = GetItemState( show_item, TVIF_STATE );
        parent = GetParentItem( show_item );
        has_children = ItemHasChildren( show_item ) || parent == NULL;
        selected = (state & TVIS_SELECTED) && ((this == GetFocus()) || 
                (tree_style & TVS_SHOWSELALWAYS));

        if ( GetItemRect( show_item, rc_item, TRUE ) )
        {
            if ( has_children  || selected )
            {
                if ( selected )
                {
                    // HERE i need to 
                }
                else

                // do some stuff...

                if ( has_children )
                {
                    HICON icon;
                    // HERE I need to load CTreeCtrl nodes _DEFAULT_icon
                    icon = LoadIcon(NULL, IDI_ASTERISK);
                    if ( icon != NULL )
                        DrawIconEx( pDC->m_hDC, rc_item.left - 18, rc_item.top, icon, 16, 16,0,0, DI_NORMAL ); 
                }
            }
            if ( !has_children )
            {
                HICON icon;
                *// HERE I need to load CTreeCtrl nodes _DEFAULT_icon*
                icon = LoadIcon(NULL, IDI_ASTERISK);
                if ( icon != NULL )
                    DrawIconEx( pDC->m_hDC, rc_item.left - 18, rc_item.top, icon, 16, 16,0,0, DI_NORMAL ); 
            }
            name = GetItemText( show_item );
            // ...
            if ( selected )
            {
                pDC->DrawText( "Temp", rc_item, DT_LEFT );
            }
            else
            {
                pDC->DrawText( "Temp", rc_item, DT_LEFT );
            }
            //if ( state & TVIS_BOLD )
            //  pDC->SelectObject( font );
        }
    } while ( (show_item = GetNextVisibleItem( show_item )) != NULL );
}

All I need, is source code of an almost-standard CTreeCtrl::OnPaint() implementation.
Any suggestion/help is appreciated. 🙂

Thanks

IT.

Answer 1

You don’t need to overload onPaint. If you set a tree items text as LPSTR_TEXTCALLBACK, the CtreeCtrl will fire the message TVN_GETDISPINFO to retrieve new text every time that item is displayed. Regeister a message handler using ON_NOTIFY if it’s in a parent window or ON_NOTIFY_REFLECT if you are subclassing CTreeCtrl. This message handler can assign the text you want but allow the treeCtrl to continue drawing as normal.

TVN_GETDISPINFO Documentation

If you went the parent Cwnd route, youd need

1. So you’d need to assign the message handler in the cpp file:

   BEGIN_MESSAGE_MAP(MyCWnd, CWnd)

   ON_NOTIFY(TVN_GETDISPINFO, tree_ctl_id, CustomTreeControl::OnGetdispinfo)
   END_MESSAGE_MAP()

2. Function prototype in header

   afx_msg void OnGetdispinfo( NMHDR* pNMHDR, LRESULT* pResult );

3. This at the end of your class definition

   DECLARE_MESSAGE_MAP()

4. And the actual function to handle the request

   void ColumnTreeControl::OnGetdispinfo(NMHDR* pNMHDR, LRESULT* pResult)
   {
   NMTVDISPINFO * pDispInfo = (NMTVDISPINFO )pNMHDR;
   TVITEM item = &pDispInfo->item;

   if(item->mask & TVIF_TEXT )
   {
            item->pszText " YOUR CODE HERE";
   }
   *pResult = 0;
   

   }