How to load default icons for CTreeCtrl nodes - mfc

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:
How can I show the DEFAULT CTreeCtrl icons? I dont'need/don't want
custom icons.
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
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()
Function prototype in header
afx_msg void OnGetdispinfo( NMHDR* pNMHDR, LRESULT* pResult );
This at the end of your class definition
DECLARE_MESSAGE_MAP()
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;
}