Re: child window drawing extends onto dialog

From:

King Menelaus <menelaus@nowhere.fake>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 11 Apr 2008 12:12:32 -0700

Message-ID:

<VLWdnfUnUrO_JWLanZ2dnUVZ_sLinZ2d@scnresearch.com>

Works beautifully. Thanks!

AliR (VC++ MVP) wrote:

You can specfiy a clip region:

void CMyCtrl::OnPaint()
{
   CPaintDC dc(this);

   CRect rect;
   GetClientRect(&rect);

   CRgn Rgn;
   CRgn *pOldRgn =
Rgn.CreateRectRgn(rect.left,rect.top,rect.right,rect.bottom);
   dc.SelectClipRgn(&Rgn,RGN_COPY);

   //do drawing here

   dc.SelectObject(pOldRgn);
}

This has got to be something obvious.

I've subclassed a static control on my dialog with a CWnd-derived class,
call it CMyControl. Here's how the control is declared in the rc file:

LTEXT "Static",IDC_STATIC_GRAPH,7,5,240,149

In CMyControl::OnPaint() I do some drawing using CPaintDC::SetPixel().
That works fine. However, if the drawing extends beyond the bounds of
CMyControl's client rectangle (which sometimes happens -- it's data being
read from a machine-control device), I would like it to not be visible.
Instead, it's being drawn onto the parent dialog's background. Do I need
to clip the data to CMyControl's rectangle myself, or is there some style
I'm missing that will do it for me? Why, if I'm drawing to CMyControl's
DC, am I seeing drawing on the dialog?