Question

As the title says.
Even with CPaintDC in the derived class the GDI drawing is not cut off.
Thanks in advance.

void CGraph::OnPaint ()
{
   CPaintDC dc(this);
   dc.SetViewportOrg (0, 400);
   dc.SetMapMode(MM_ISOTROPIC);
   dc.SetWindowExt(1000, 800);
   dc.SetViewportExt(1000, -800);

   // MessageBox(L"OnPaint");
   ProcessData ();
   DrawCoordinateSystem (&dc);
   DrawGrid (&dc);
   DrawGraph (&dc);
}

Answer 1

Here is the way I solved the problem

    CDC* pDC = GetDC();
    CRect rClient(0,0,1000,800);
    //GetClientRect(rClient);
    CRgn ClipRgn;

    if (ClipRgn.CreateRectRgnIndirect(&rClient))
    {
        pDC->SelectClipRgn(&ClipRgn);
    }

    pDC->SelectObject (PenBlack);
    pDC->MoveTo (-leftMargin*zoomWidth, setPointsCorrected);
    pDC->LineTo (1000*zoomWidth, setPointsCorrected);

    pDC->SelectClipRgn(NULL);
    ReleaseDC(pDC);