Setting color and font attribute for individual items

There are some constraints that have to be adhered to. Since the tree view control computes the height of the items ( all items have the same height ) based on the window font, if we change the font size we can only decrease it so that the text does not overlap with the other labels. Also, the tree view control, automatically manages the horizontal scrollbar, so it is better to maintain the width of the label.
 

Step 1: Add member variable to track font and color

protected:
	struct Color_Font
	{
		COLORREF color;
		LOGFONT  logfont;
	};
	CMap< void*, void*, Color_Font, Color_Font& > m_mapColorFont ;

Step 2: Add helper functions to get/set font and color

void CTreeCtrlX::SetItemFont(HTREEITEM hItem, LOGFONT& logfont)
{
	Color_Font cf;
	if( !m_mapColorFont.Lookup( hItem, cf ) )
		cf.color = (COLORREF)-1;
	cf.logfont = logfont;
	m_mapColorFont[hItem] = cf;
}

void CTreeCtrlX::SetItemBold(HTREEITEM hItem, BOOL bBold)
{
	SetItemState( hItem, bBold ? TVIS_BOLD: 0, TVIS_BOLD );
}

void CTreeCtrlX::SetItemColor(HTREEITEM hItem, COLORREF color)
{
	Color_Font cf;
	if( !m_mapColorFont.Lookup( hItem, cf ) )
		cf.logfont.lfFaceName[0] = '\0';
	cf.color = color;
	m_mapColorFont[hItem] = cf;
}

BOOL CTreeCtrlX::GetItemFont(HTREEITEM hItem, LOGFONT * plogfont)
{
	Color_Font cf;
	if( !m_mapColorFont.Lookup( hItem, cf ) )
		return FALSE;
	if( cf.logfont.lfFaceName[0] == '\0' ) 
		return FALSE;
	*plogfont = cf.logfont;
	return TRUE;

}

BOOL CTreeCtrlX::GetItemBold(HTREEITEM hItem)
{
	return GetItemState( hItem, TVIS_BOLD ) & TVIS_BOLD;
}

COLORREF CTreeCtrlX::GetItemColor(HTREEITEM hItem)
{
	// Returns (COLORREF)-1 if color was not set
	Color_Font cf;
	if( !m_mapColorFont.Lookup( hItem, cf ) )
		return (COLORREF)-1;
	return cf.color;

}

Step 3: Add WM_PAINT handler

In the first implementation, I let the control directly draw on the screen and then redrew the items that had a different font or color. This caused a visible flicker as the items got updated a second time. To overcome this we use a memory device context for all the updates and finally we copy this to the main device context. After creating a compatible DC, we add a compatible bitmap to the memory DC and set the clip region to be the same as the paint DC.

After the default window procedure for the control has updated the device context, we scan through all the visible items and update the items that have a user defined color or font.

void CTreeCtrlX::OnPaint() 
{
	CPaintDC dc(this);

	// Create a memory DC compatible with the paint DC
	CDC memDC;
	memDC.CreateCompatibleDC( &dc );

	CRect rcClip, rcClient;
	dc.GetClipBox( &rcClip );
	GetClientRect(&rcClient);

	// Select a compatible bitmap into the memory DC
	CBitmap bitmap;
	bitmap.CreateCompatibleBitmap( &dc, rcClient.Width(), rcClient.Height() );
	memDC.SelectObject( &bitmap );
	
	// Set clip region to be same as that in paint DC
	CRgn rgn;
	rgn.CreateRectRgnIndirect( &rcClip );
	memDC.SelectClipRgn(&rgn);
	rgn.DeleteObject();
	


	// First let the control do its default drawing.
	CWnd::DefWindowProc( WM_PAINT, (WPARAM)memDC.m_hDC, 0 );


	HTREEITEM hItem = GetFirstVisibleItem();

	int n = GetVisibleCount()+1;
	while( hItem && n--)
	{
		CRect rect;

		// Do not meddle with selected items or drop highlighted items
		UINT selflag = TVIS_DROPHILITED | TVIS_SELECTED;
		Color_Font cf;
	
		if ( !(GetItemState( hItem, selflag ) & selflag ) 
			&& m_mapColorFont.Lookup( hItem, cf ))
		{
			CFont *pFontDC;
			CFont fontDC;
			LOGFONT logfont;

			if( cf.logfont.lfFaceName[0] != '\0' ) 
			{
				logfont = cf.logfont;
			}
			else
			{
				// No font specified, so use window font
				CFont *pFont = GetFont();
				pFont->GetLogFont( &logfont );
			}

			if( GetItemBold( hItem ) )
				logfont.lfWeight = 700;
			fontDC.CreateFontIndirect( &logfont );
			pFontDC = memDC.SelectObject( &fontDC );

			if( cf.color != (COLORREF)-1 )
				memDC.SetTextColor( cf.color );

			CString sItem = GetItemText( hItem );

			GetItemRect( hItem, &rect, TRUE );
			memDC.SetBkColor( GetSysColor( COLOR_WINDOW ) );
			memDC.TextOut( rect.left+2, rect.top+1, sItem );
			
			memDC.SelectObject( pFontDC );
		}
		hItem = GetNextVisibleItem( hItem );
	}


	dc.BitBlt( rcClip.left, rcClip.top, rcClip.Width(), rcClip.Height(), &memDC, 
				rcClip.left, rcClip.top, SRCCOPY );
}

Step 4: Go ahead and change the item font or color

	// Change the item color to red
	SetItemColor( hItem, RGB(255,0,0));

	// Change the item to italicized font and underlined
	LOGFONT logfont;
	CFont *pFont = GetFont();
	pFont->GetLogFont( &logfont );
	logfont.lfItalic = TRUE;
	logfont.lfUnderline = TRUE;
	SetItemFont(hti, logfont );