Step 1: Add member variable to track font and color
Since the control has no support for item font or color, we have to track this information within our program. We use a CMap object to associate these properties with the tree items. The map will contain information for only those items that we explicitly change. We define a nested structure that is used with the CMap object, to hold the color and the font information.
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
Define the helper functions to get or set the item font or color. To set the font, we actually pass the logfont rather than a font handle. Also note that we have defined a pair of functions to get and set the bold attribute. There are two reasons for providing a separate function for the bold attribute although we can use the font function. The first reason is that the tree view control directly supports setting an item to bold. Secondly, using the built in support also maintains the proper setting for the horizontal scrollbar.
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 this function we first let the control update a memory device context. We then redraw the visible labels using the user defined attributes. We let the control handle the highlighting of items, so before we update a label we make sure that it is not selected or drophilited. Also, if the items font or color attributes were not changed, we don't need to redraw it. Once all the updates are ready in the memory device context, we blit it to the actual device context.
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
Here are some examples.
// 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 );
