FILE: Using Fonts in ATL Controls with NiceText.exe

• Microsoft Active Template Library, versions 2.0, 2.1, 3.0

SUMMARY

Active Template Library (ATL) programmers creating ActiveX controls that display text may find it beneficial to allow the user of the control to select the font that the text is drawn in. ATL provides some functionality for a stock font property, or you may choose to use a custom font property. In ATL ActiveX controls, the steps to implement a custom or stock font property are practically the same. The More Information section of this article describes the steps to take to add a stock font property to your ATL ActiveX control. The NiceText sample shows how to implement an ATL control that uses a stock font property.

NiceText.exe is a self-extracting executable file that contains the source files for the NiceText control.

NiceText.exe is available for download from the Microsoft Software Library:

~ NiceText.exe

Q119591 How to Obtain Microsoft Support Files from Online Services

MORE INFORMATION

Use these steps to create a control with a stock font property:

1. Open an existing ATL in-proc server project or create a new one.



2. Using the ATL Object Wizard, insert a new ATL control into your project. Give the control a name, then select the Stock Properties tab. From the Stock Properties tab, select the Font property and insert it into your control. Completing this step adds an interface definition such as the following to your projects Interface Definition Language file (.idl file). The interface definition in your .idl file looks similar to the following:

   
         [
            object,
            uuid(E882D672-878E-11D0-B00C-000000000000),
            dual,
            helpstring("INiceTextCtrl Interface"),
            pointer_default(unique)
         ]
         interface INiceTextCtrl : IDispatch
         {
            [propputref, id(DISPID_FONT)]
            HRESULT Font([in]IFontDisp* pFont);
            [propput, id(DISPID_FONT)]
            HRESULT Font([in]IFontDisp* pFont);
            [propget, id(DISPID_FONT)]
            HRESULT Font([out, retval]IFontDisp** ppFont);
         }; 

   In order for your control's Font property to work correctly in most control containers, you need to move this interface definition from outside the Library block in your .idl file to inside the Library block. You also need to remove the #import for Ucidl.idl from the .idl file. Your .idl file now has a Library section that looks like the following:

   
         [
            uuid(E882D665-878E-11D0-B00C-000000000000),
                 version(1.0),
                 helpstring("nicetext 1.0 Type Library")
         ]
         library NICETEXTLib
         {
                 importlib("stdole32.tlb");
                 importlib("stdole2.tlb");
   
                 [    object,
                         uuid(E882D672-878E-11D0-B00C-000000000000),
                         dual,
                         helpstring("INiceTextCtrl Interface"),
                         pointer_default(unique)
                 ]
                 interface INiceTextCtrl : IDispatch
                 {
                         [propputref, id(DISPID_FONT)]
                         HRESULT Font([in]IFontDisp* pFont);
                         [propput, id(DISPID_FONT)]
                         HRESULT Font([in]IFontDisp* pFont);
                         [propget, id(DISPID_FONT)]
                         HRESULT Font([out, retval]IFontDisp** ppFont);
                 };
   
                 [
                         uuid(E882D673-878E-11D0-B00C-000000000000),
                         helpstring("NiceTextCtrl Class") ]
                         coclass NiceTextCtrl
                 {
                         [default] interface INiceTextCtrl;
                 };
         }; 

   This step also adds a member variable named m_pFont to your control's implementation class to hold the Font property. The get, put, and putref functions for the stock Font property are implemented by ATL in the CStockPropImpl class inside Atlctl.h. If you are implementing a non- stock Font property, you have to add the get, put, or putref functions manually if you are using Visual C++ 4.2b. If you are using Visual C++ 5.0, you can use the interface browser to add the property, which adds the property get and put functions for you.



3. Add a static variable of type FONTDESC to your control's .cpp file. The FONTDESC structure holds the default description of your Font property. You can create and initialize the variable in the same step as follows:

   
         static const FONTDESC _fontdesc =
         {sizeof(FONTDESC), OLESTR("times new roman"), FONTSIZE( 14 ),
         FW_BOLD, ANSI_CHARSET, TRUE, FALSE, FALSE }; 




4. Add an entry to your control's property map for the stock Font such as the following:

   
         PROP_ENTRY("Font", DISPID_FONT, CLSID_MSStockFont) 

   NOTE: You also need to #include <ATLCTL.H>



5. Change your control's drawing code so it uses your font property to draw text. Here is an example of drawing code you could add to an ATL control's OnDraw member function:

   
         HFONT hStockFont=NULL,hOldFont=NULL;
          CComQIPtr<IFont,&IID_IFont> pFont(m_pFont);
          TCHAR msg[50];
          wsprintf(msg,_T("Current Thread is %x"),GetCurrentThreadId());
          if(pFont)
             pFont->get_hFont(&hStockFont);
          if(hStockFont)
                  hOldFont = (HFONT)SelectObject(di.hdcDraw,hStockFont);
          DrawText(di.hdcDraw, msg, -1, &rc, DT_CENTER | DT_VCENTER |
                   DT_SINGLELINE);
          if(hOldFont)
             SelectObject(di.hdcDraw,hOldFont); 




6. It is recommended that you implement a sink object to connect to the Font object's property notification source so that your control updates its rendering with the correct font properties when a client changes one of your font's properties. COM-based fonts support an outgoing interface based on the IPropertyNotifySink interface to notify font users when properties of the font, such as name or weight, are about to change and after they have been changed. To receive notification of these changes, add a class to your project that implements the IPropertyNotifySink interface. Then, an instance of this class can be created by the control and a pointer to it passed to the Font object's connection point. Your control then receives notifications from the Font object if its properties change, which allows you to update your control's text accordingly.
   
   The following class implements an IPropertyNotifySink interface and can be used for receiving notifications from a Font object. This class also holds a back pointer to the parent control object so that it can update the control when properties change. This class is added to the control's header file before the declaration of the control's class:

   
         class CNiceTextCtrl; //forward definition of parent class
         class ATL_NO_VTABLE CFontNotifyImpl :
                 public CComObjectRootEx<CComSingleThreadModel>
                 public IPropertyNotifySink
         {
         public:
                 CFontNotifyImpl():m_pParent(NULL){}
         BEGIN_COM_MAP(CFontNotifyImpl)
                 COM_INTERFACE_ENTRY(IPropertyNotifySink)
         END_COM_MAP()
   
         public:
                 STDMETHOD(OnChanged)(DISPID dispid);
                 STDMETHOD(OnRequestEdit)(DISPID dispid){return S_OK;}
   
                 DWORD m_FontNotifyCookie;
                 void SetParent(CNiceTextCtrl *pParent){m_pParent = pParent;}
                 CNiceTextCtrl *m_pParent;
         }; 

   To your control, add a protected member variable that holds a sink object:

   
         CComObject<CFontNotifyImpl> *m_pFontNotifySink; 

   Initialize the sink object in your control's constructor:

   
         CComObject<CFontNotifyImpl>::CreateInstance(&m_pFontNotifySink);
         m_pFontNotifySink->SetParent(this); 




7. Initialize the font object for the control and hook up the sink interface. A good place to do this is in SetClientSite. SetClientSite is called when a control first begins to interact with a container, soon after the control object is created on behalf of a container. To override SetClientSite. add it as a member of your control class by adding the following to your control's header file inside your class declaration:

   
         STDMETHOD(SetClientSite)(LPOLECLIENTSITE pSite); 

   And implement it in your object's .cpp file like this:

   
         STDMETHODIMP CNiceTextCtrl::IOleObject_SetClientSite
                                                       (LPOLECLIENTSITE pSite)
         {
         HRESULT hr = CComControlBase::IOleObject_SetClientSite(pSite);
         // Check to see if the container has an ambient font. If it does,
         // clone it so your user can change the font of the control
         // without changing the ambient font for the container. If there is
         // no ambient font, create your own font object when you hook up a
         // client site.
   
         if(!m_pFont && pSite)
         {
            FONTDESC fd = _fontdesc;
            CComPtr<IFont> pAF;
            CComPtr<IFont> pClone;
         if(SUCCEEDED(GetAmbientFont(&pAF)))
          {
              //clone the font
             if(SUCCEEDED(pAF->Clone(&pClone)))
                 pClone->QueryInterface(IID_IFontDisp, (void**)&m_pFont);
   
          }
          else
          {
             OleCreateFontIndirect(&fd,IID_IFontDisp,(void**)&m_pFont);
          }
          //also, hook up a notify sink
          if(m_pFont&&m_pFontNotifySink)
          {
             //smart pointers will release themselves
           CComQIPtr<IConnectionPointContainer,&IID_IConnectionPointContainer>
           pCPC(m_pFont);
           CComPtr<IConnectionPoint> pCP;
           if(pCPC)
           {
              pCPC->FindConnectionPoint(IID_IPropertyNotifySink,&pCP);
              if(pCP)
              {
                  pCP->Advise((IUnknown*)m_pFontNotifySink,
                         &m_pFontNotifySink->m_FontNotifyCookie);
              }
           }
         }
        }
         return hr;
         } 




8. Have the sink interface update the control when font properties change:

   
         STDMETHODIMP CFontNotifyImpl::OnChanged(DISPID dispid)
         {
                 ATLTRACE(_T("OnChanged sink: %x\n"),this);
            m_pParent->FireViewChange();
            return S_OK;
         } 

Additional query words: font ATL stock property

Keywords          : kbprg kbusage kbATL kbATL200 kbATL210 kbCtrl kbATL300 
Version           : 2.0 2.1 3.0
Platform          : WINDOWS 
Issue type        : kbhowto 

Last Reviewed: July 22, 1999