HOWTO: Draw Controls in an OLE Metafile

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++ for Windows, 16-bit edition, versions 1.5, 1.51, 1.52
  • Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 4.0, 4.1, 5.0

SUMMARY

You can use controls, either directly on a CView or from a dialog template on a CFormView, in an OLE enabled MFC application. However, when the item is embedded but not active, the controls on these views will not be drawn to the Windows metafile supplied to the COleServerItem::OnDraw() function. In this case, you must "draw" the controls manually into the metafile. This article shows you how.

MORE INFORMATION

The simplest way to get controls to "draw" in a metafile is to use the same method the VIEWEX sample uses to draw its CInputView to a printer device context. VIEWEX's OnPrint routine draws each control as a rectangle, circle, text, and so on. Override the COleServerItem::OnDraw() function and insert your code into it. As an example, use the COleServerItem::OnDraw() function listed in this article; it shows both the VIEWEX code to insert in the OnDraw member function and the helper function PaintChildWindows() that actually does the painting of each control.

Sample Code

/* Compile options needed: Standard
*/ 

void CMyServerItem::OnDraw(CDC* pDC) // pDC is actually a metafile
{
    //BLOCK: Set up scale mode
    {
        CClientDC dcScreen(NULL);
        pDC->SetMapMode(MM_ANISOTROPIC);
        // map 1 screen logical inch to 1 printer (/output) logical inch
        pDC->SetWindowExt(dcScreen.GetDeviceCaps(LOGPIXELSX),
                dcScreen.GetDeviceCaps(LOGPIXELSX));
        pDC->SetViewportExt(pDC->GetDeviceCaps(LOGPIXELSX),
                pDC->GetDeviceCaps(LOGPIXELSX));
    }
    // we must also offset the window positions relative to the scroll
    // offset

    // We cheat here since some controls do not paint if they are
    // invisible, so we temporary make set the appropriate visible bits
    // during preview mode so the controls think they are visible even
    // though they aren't.

    HWND hWndCheatVisible = NULL;
    if (!IsWindowVisible())
    {
        // walk up to the top until we find the invisible window
        for (HWND hWnd = m_hWnd;
            hWnd != NULL; hWnd = ::GetParent(hWnd))
        {
            ASSERT(hWnd != NULL);
            DWORD dwStyle = ::GetWindowLong(hWnd, GWL_STYLE);
            if ((dwStyle & WS_VISIBLE) == 0)
            {
                ::SetWindowLong(hWnd, GWL_STYLE, dwStyle | WS_VISIBLE);
                hWndCheatVisible = hWnd;
                break;
            }
        }
        ASSERT(hWndCheatVisible != NULL);
    }

    CPen pen(PS_SOLID, 1, RGB(0,0,0));  // solid black pen
    CPen* pOldPen = pDC->SelectObject(&pen);

    ASSERT(pDC->GetWindowOrg() == CPoint(0,0));
    CRect pRect = new CRect(-50,-50,600,600);

    PaintChildWindows(m_hWnd, pDC, GetDeviceScrollPosition());
    ASSERT(pDC->GetWindowOrg() == CPoint(0,0));
    pDC->SelectObject(pOldPen);

    if (hWndCheatVisible != NULL)
        ::SetWindowLong(hWndCheatVisible, GWL_STYLE,
            ::GetWindowLong(hWndCheatVisible, GWL_STYLE) &~ WS_VISIBLE);
}

void CMyServerItem::PaintChildWindows(HWND hWndParent,
                                      CDC* pDC, CPoint ptOffset)
{
    for (HWND hWndChild = ::GetTopWindow(hWndParent);
        hWndChild != NULL;
        hWndChild = ::GetNextWindow(hWndChild, GW_HWNDNEXT))
    {
        CRect rect;
        ::GetWindowRect(hWndChild, rect);  // wnd rect in screen coords
        ScreenToClient(&rect);             // relative to this view

        HDC hdcOut = pDC->m_hDC;
#ifdef _DEBUG
        CPoint pt = pDC->GetWindowOrg();
        ASSERT(pt.x == 0 && pt.y == 0);
#endif

        DWORD dwStyle = ::GetWindowLong(hWndChild, GWL_STYLE);
        if (dwStyle & (WS_HSCROLL|WS_VSCROLL))
        {
            TRACE("Warning: printing control with scrollbars not
 supported\n");
        }
        if (dwStyle & WS_BORDER)
        {
            // the only case we special case - manually drawn border
            ::Rectangle(hdcOut, rect.left, rect.top, rect.right,
                        rect.bottom);
            rect.InflateRect(-1,-1);        // 1 logical pixel
        }

        pDC->SaveDC();
        {
            CPoint pt(ptOffset.x + rect.left, ptOffset.y + rect.top);
            pDC->LPtoDP(&pt);
            pDC->OffsetViewportOrg(pt.x, pt.y);
                // set the viewport origin so that the window origin
                //  can be changed by the control

            // draw it using a non-virtual HDC
            ::SendMessage(hWndChild, WM_PAINT, (WPARAM)hdcOut, 0L);
        }
        pDC->RestoreDC(-1);

        if (::GetTopWindow(hWndChild) != NULL)
            PaintChildWindows(hWndChild, pDC, ptOffset);
    }
} 

Additional query words: mfc ole inplace embed

Keywords : kbole kbMFC kbVC
Version : WINDOWS:1.5,1.51,1.52,2.0,2.1,4.0,5.0
Platform : NT WINDOWS
Issue type : kbhowto