Re: Transparent CStatic on Dialog with image in background

From:

"David Ching" <dc@remove-this.dcsoft.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 14 Aug 2007 11:20:40 -0700

Message-ID:

<Xnmwi.3806$i85.3719@nlpi061.nbdc.sbc.com>

<maik.wiege@googlemail.com> wrote in message
news:1187113136.831271.24300@g4g2000hsf.googlegroups.com...

Hi everyone!

I'm developing a little program for windows mobile (think problem
should be the same for Win32) in MFC and have problems displaying a
dialog with an JPEG-image in the background and placing some
transparent CStatic's above it.
Here is what I dit:

BOOL CMyDialog::OnEraseBkgnd(CDC * pDC)
{
BOOL bRet = CDialog::OnEraseBkgnd(pDC);

// draw background image
CComPtr<IImagingFactory>pFactory;
HRESULT hr = pFactory.CoCreateInstance(CLSID_ImagingFactory);
IImage* pImg;
hr = pFactory->CreateImageFromFile(_T("\\myBackImage.jpg"), &pImg);
RECT a; a.bottom = 320; a.left = 0; a.right = 240; a.top = 0;
pImg->Draw(pDC->m_hDC, &a, NULL);

return bRet;
}

To optimize, create the factory in OnInitDialog(), and not in OnEraseBkgnd()
which can be called many times while the dialog is displayed.

HBRUSH CAlarmDialog::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);

if(nCtlColor==CTLCOLOR_STATIC)
{
m_nullBrush.CreateStockObject(NULL_BRUSH);//m_bgBrush;
pDC->SetBkMode(TRANSPARENT);
return m_nullBrush;
}
return hbr;
}

The reason why I have to use the CComPtr things is because
CImage::Load() is not supported by Windows Mobile, but this seems not
to be the problem. The image is drawn to the background, but the areas
of the static controls is not painted at all, meaning the background
of the statics show the previous dialog "behind it" and the areas
surrounding them show the correct image.
What am I missing here?

In your dialog's PreCreateWindow(), disable WS_CLIPCHILDREN so that when you
paint the background image, it covers the areas occupied by the child
windows... necessary because some of your child windows don't render
anything.

-- David