Re: CListCtrl size at runtime

From:

"AliR $VC++ MVP$" <AliR@online.nospam>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 2 Dec 2008 15:00:29 -0600

Message-ID:

<imhZk.1466$jZ1.940@flpi144.ffdc.sbc.com>

CMemDC is pretty cool. It is simply an extention of CDC that automatically
creates a bitmap and selects it into the memory dc, and when the destructor
is called it bitblts it content onto the original dc.

http://www.codeproject.com/KB/GDI/flickerfree.aspx

AliR.

"Tom Serface" <tom.nospam@camaswood.com> wrote in message
news:C121425E-5320-4180-B872-448D3AB651DD@microsoft.com...

I've never tried the CMemDC method so I can't comment, but I'm glad it
worked for him. I've never noticed any annoying flicker either so I
probably would try to get rid of it if I were writing that often to my
list control. This is useful information for that eventuality.

Tom

"Giovanni Dicanio" <giovanniDOTdicanio@REMOVEMEgmail.com> wrote in message
news:eQSkEaWTJHA.3668@TK2MSFTNGP03.phx.gbl...

Hi Tom,

I think that 10 updates per seconds are few :)

I tried 100 updates in less than a second, and using the technique of
painting to a CMemDC (as I posted above), I have zero flickering.

I belive the key here is to use CMemDC as described here:

http://69.10.233.10/KB/GDI-plus/what_is_a_basename_.aspx

The handlers for WM_ERASEBACKGROUND, WM_PAINT and WM_SIZE for a class I
derived from CListCtrl are like these:

<code>
BOOL CMyListCtrl::OnEraseBkgnd(CDC* pDC)
{
   // TODO: Add your message handler code here and/or call default

   UNUSED_ALWAYS(pDC);

   // return CListCtrl::OnEraseBkgnd(pDC);

   return TRUE;
}

void CMyListCtrl::OnSize(UINT nType, int cx, int cy)
{
   CListCtrl::OnSize(nType, cx, cy);

   GetClientRect(m_rectClient);

   CHeaderCtrl* pHC;
   pHC = GetHeaderCtrl();
   if (pHC != NULL)
   {
       CRect rectHeader;
       pHC->GetItemRect( 0, &rectHeader );
       m_rectClient.top += rectHeader.bottom;
   }
}

void CMyListCtrl::OnPaint()
{
   CPaintDC dc(this); // device context for painting

   // Paint to a memory device context to reduce screen flicker.
   CodeProject::CMemDC memDC(&dc, &m_rectClient);

   // Let the window do its default painting...
   CWnd::DefWindowProc( WM_PAINT, (WPARAM)memDC.m_hDC, 0 );
}

</code>

Note that I used a custom CodeProject:: namespace above, because it seems
that VS2008 SP1 (ex Feature pack) defines a new CMemDC class (but I
wanted to use the CodeProject's one).

I use also a LVN_GETDISPINFO notification in is reflected form, such that
it can be handled in the CListCtrl-derived class, and the body of this
handler is something like this:

<code>
void CMyListCtrl::OnLvnGetdispinfo(NMHDR *pNMHDR, LRESULT *pResult)
{
   NMLVDISPINFO *pDispInfo = reinterpret_cast<NMLVDISPINFO*>(pNMHDR);
   *pResult = 0;

   if (pDispInfo->item.iItem < 0 ||
       pDispInfo->item.iItem >= GetDB()->Count())
   {
           return; // requesting invalid item
   }

   if (pDispInfo->item.mask & LVIF_TEXT) {
       const Database::Record * pRec =
GetDB()->GetAt(pDispInfo->item.iItem);

       LPCTSTR pszResult = TEXT("");
       switch (pDispInfo->item.iSubItem)
       {
          case COL_NAME: pszResult = pRec->Name.GetString(); break;
          case COL_SURNAME: pszResult = pRec->Surname.GetString();
break;
          case COL_CITY: pszResult = pRec->City.GetString(); break;
       }
       pDispInfo->item.pszText = const_cast<LPTSTR>(pszResult);
   }

   if (pDispInfo->item.mask & LVIF_IMAGE) {
       pDispInfo->item.iImage = -1;
   }

   if (pDispInfo->item.mask & LVIF_STATE) {
       pDispInfo->item.state = 0;
   }
}

</code>

G