C / C++ / MFC

void CTrafficView::OnPrepareDC(CDC *pDC, CPrintInfo *pInfo)
{
	CScrollView::OnPrepareDC(pDC, pInfo);

	pDC->SetMapMode(MM_ANISOTROPIC);	// for scaling
	pDC->SetWindowExt(m_DrawArea);		// in logical units

	int xExtent = m_Scale * m_DrawArea.cx;
	int yExtent = m_Scale * m_DrawArea.cy;
	pDC->SetViewportExt(xExtent, yExtent);

	// keep the road divider in the centre of screen
	// by moving the viewport origin
	GetClientRect(&m_ClientRect);	// the height of the window
	CPoint viewOrg;
	viewOrg.y = m_ClientRect.Height()/2;	// - yExtent/2;
	viewOrg.x = m_Border_Lhs*m_Scale;

	viewOrg -= GetDeviceScrollPosition();	// so scrolling accounted for
	pDC->SetViewportOrg(viewOrg);
}

void CTrafficView::ResetScrollBars()
{
	// set up device context and new scroll sizes
	CClientDC aDC(this);
	OnPrepareDC(&aDC);
	CSize temp = m_DrawArea;	// since we don't want drawArea changed
	aDC.LPtoDP(&temp);
	SetScrollSizes(MM_TEXT, temp);
}

void CTrafficView::OnToolsZoomin() 
{
	// move scrolls bars to centre of logical view
	CPoint pt;
	GetClientRect(&m_ClientRect);
        pt.x = (m_ClientRect.Width()  / 2);
        pt.y = (m_ClientRect.Height() / 2);
	
	CClientDC aDC(this);
	OnPrepareDC(&aDC);
	CPoint vp = aDC.GetViewportOrg();

	pt = pt - vp;	// adjust device point to viewport point

	CScrollView::ScrollToPosition(pt);	// scroll to viewport point

	m_Scale += 0.2;				// MAGIC NUMBER - should it be an option?
	ResetScrollBars();
	
	Invalidate();	// draw it
}

PIXELFORMATDESCRIPTOR pfd;

int maxpf = DescribePixelFormat(hDC,0,0,NULL);
for (int i = 1; i <= maxpf; i++)
{
   if (DescribePixelFormat(hDC,i,sizeof(PIXELFORMATDESCRIPTOR),&pfd) == 0)
      continue;
   if ((pfd.dwFlags & PFD_SUPPORT_OPENGL) == 0)
      continue;

   if ((pfd.dwFlags & PFD_GENERIC_ACCELERATED) != 0)
   {
      TRACE1("%d: ACCELERATED\n", i);
   }
   else if ((pfd.dwFlags & PFD_GENERIC_FORMAT) != 0)
   {
      TRACE1("%d: GENERIC\n", i);
   }
   else
   {
      TRACE1("%d: NONE\n", i);
   }
}