CBasePropertyPage Class

The CBasePropertyPage class is an abstract class for implementing a property page. Use this class if you are writing a filter (or other object) that supports property pages.

A property page is a COM object, so you must generate a GUID for the class identifier (CLSID) and provide an entry in the CFactoryTemplate array. For more information, see DirectShow and COM. The following example shows a typical class factory entry:

CFactoryTemplate g_Templates[] =
{   
    { 
        L"My Property Page",
        &CLSID_MyPropPage,
        CMyProp::CreateInstance,
        NULL,
        NULL
    },
    /* Also include the template for your filter (not shown). */
};

Your filter must expose the ISpecifyPropertyPages interface. This interface contains a single method, GetPages, which returns the CLSID of the property page. The following example shows how to implement this method:

STDMETHODIMP CMyFilter::GetPages(CAUUID *pPages)
{
    if (!pPages) return E_POINTER;

    pPages->cElems = 1;
    pPages->pElems = reinterpret_cast<GUID*>(CoTaskMemAlloc(sizeof(GUID)));
    if (pPages->pElems == NULL) 
    {
        return E_OUTOFMEMORY;
    }
    *(pPages->pElems) = CLSID_MyPropPage;
    return S_OK;
} 

Remember to override the filter's NonDelegatingQueryInterface method as well. For more information, see DirectShow and COM and INonDelegatingUnknown.

Next, create the dialog as a resource in your project, and create a string resource that holds the dialog title. Both of these resource IDs are parameters to the CBasePropertyPage constructor. Keeping the title string in a resource makes it easier to localize your property page.

The CBasePropertyPage class provides a framework for the IPropertyPage interface. This framework calls a number of virtual methods, including CBasePropertyPage::OnActivate, CBasePropertyPage::OnApplyChanges, and so on. In the base class, these methods simply return S_OK. Your derived class will need to override some or all of these virtual methods. For details, see the remarks for the individual methods.

Requirements

Header: Declared in Cprop.h; include Streams.h.

Library: Use Strmbase.lib (retail builds) or Strmbasd.lib (debug builds).