Re: Transarent controls

From:

mosfet <john.doe@anonymous.org>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 30 Oct 2007 11:12:14 +0100

Message-ID:

<4727037e$0$11629$426a74cc@news.free.fr>

mosfet a ?crit :

Hi,

When I search after information about transparency, it seems there are
so many ways of doing it and so many interpretation that I am a bit lost.
I am interested in a simple transparency, I mean I have a CDialog with a
bitmap in the background(drawn in OnEraseBackground) and some controls
on it (labesl, editbox, ...).
I would like to have transparent controls, CStatic, CEdit, how can I do
that ?

Let's say I have the current implementation (CMemDC is avalaible
http://www.codeproject.com/gdi/flickerfree.asp) :

CxStatic::CxStatic():CStatic(),
m_hBitmap(NULL)
{
    m_bTransparent = TRUE;
    m_bAutoWrapping = TRUE;
    m_eImgMode = FitControl;
    m_pFont = NULL;
    m_clrText = ::GetSysColor(COLOR_WINDOWTEXT);
    m_clrBkgnd = ::GetSysColor(COLOR_CAPTIONTEXT);
    m_pBrush = new CBrush(m_clrBkgnd);
}

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

    CRect rcClient;
    GetClientRect( &rcClient );

    CMemDC memDC(&dc, &rcClient, TRUE);

    // draw the backgound, text and bitmap.
    CxStatic::DrawBackground( &memDC, rcClient );
    CxStatic::DrawBitmap( &memDC, rcClient );

    // - Copy the memory device context back into the original DC via
BitBlt().
    dc.BitBlt(rcClient.left, rcClient.top, rcClient.Width(),
rcClient.Height(), &memDC, 0,0, SRCCOPY);
}

void CxStatic::DrawBackground(CDC* pDC, CRect& rcItem)
{
    if ((m_hBitmap != NULL) || (pDC == NULL) || (m_bTransparent))
        return;

    pDC->FillRect(rcItem, m_pBrush);
}

void CxStatic::DrawBitmap(CDC* pDC, CRect& rcItem)
{
    CDC dcMem;
    BITMAP bmInfo = {0};
    bmInfo.bmWidth = rcItem.Width();
    bmInfo.bmHeight = rcItem.Height();

    if (m_hBitmap == NULL)
        return;

    // Get parent DC and retrieve current background
    if (m_bTransparent)
    {
        ??????
    }

    VERIFY( dcMem.CreateCompatibleDC(pDC) );

    if (m_eImgMode == FitControl)
    {
        if (::GetObject(m_hBitmap, sizeof(BITMAP), &bmInfo) == 0)
            return;
    }
    HBITMAP* pBmpOld = (HBITMAP*) ::SelectObject(dcMem.m_hDC, m_hBitmap);

    SetStretchBltMode(pDC->m_hDC, BILINEAR);

    pDC->StretchBlt(0,0,
        rcItem.Width(), rcItem.Height(),&dcMem,0,0,
        bmInfo.bmWidth, bmInfo.bmHeight,
        SRCCOPY);
}