Re: Transarent controls

mosfet <>
Tue, 30 Oct 2007 16:08:19 +0100
Ok I have rewritten the control with your suggestions.
I am using reference instead of pointer for DC, I am using a CBitmap, ...

I just don't understand the part about not taking the parent device...

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 );

    // For now let's ignore text drawing
    //CxStatic::DrawText( memDC, rcClient );

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


void CxStatic::DrawBitmap(CDC& dc, CRect& rcItem)
    CDC dcMem;
    CBitmap bmp;
    CBitmap* pOldBmp = NULL;

    TRACE( _T("rcItem : Width = %d, Height = %d\n"), rcItem.Width(),
rcItem.Height() );
    if (m_bTransparent == TRUE)
        TRACE( _T("CxStatic::DrawBitmap : Transparent is enabled\n") );

        // Get parent DC and retrieve current background
        CDC* pParentDC = GetParent()->GetDC();
        if (pParentDC != NULL)
            CRect crect, wrect;

            // Create a Bitmap holding parent bmp
            VERIFY( dcMem.CreateCompatibleDC( pParentDC ) );
            bmp.CreateCompatibleBitmap(pParentDC, wrect.Width(),wrect.Height());
            pOldBmp = dcMem.SelectObject( &bmp );
            //m_hBitmap = ::CreateCompatibleBitmap ( pParentDC->m_hDC,
wrect.Width(), wrect.Height() );
            //pOldBmp = (HBITMAP*) ::SelectObject(dcMem.m_hDC, m_hBitmap);
            dcMem.BitBlt(0,0, wrect.Width(), wrect.Height(), &dc,

        if (m_Bmp.GetSafeHandle() == NULL)

        pOldBmp = dcMem.SelectObject( &m_Bmp );
        //pOldBmp = (HBITMAP*) ::SelectObject(dcMem.m_hDC, m_hBitmap);

        BITMAP bmInfo;
        if (m_eImgMode == FitControl)
            if( m_Bmp.GetBitmap(&bmInfo) == 0)

        ::SetStretchBltMode(dc.m_hDC, BILINEAR);
            rcItem.Width(), rcItem.Height(),&dcMem,0,0,
            bmInfo.bmWidth, bmInfo.bmHeight,

    ::SelectObject(dcMem.m_hDC, pOldBmp);

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