Re: CListCtrl size at runtime

From:

"Giovanni Dicanio" <giovanniDOTdicanio@REMOVEMEgmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Sun, 23 Nov 2008 13:24:41 +0100

Message-ID:

<eQSkEaWTJHA.3668@TK2MSFTNGP03.phx.gbl>

"Tom Serface" <tom.nospam@camaswood.com> ha scritto nel messaggio
news:AD3BBE0D-1E6C-4A20-BC12-7838B4A543D9@microsoft.com...

That is a great idea for Gary to try, but he may find out that the flicker
is because it is updating too fast rather than the opposite. I think the
control is just scrolling quickly and always pinning it to the bottom
makes a lot of calls to EnsureVisible() happen (I think he said as many as
10 a second).

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