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Retrieving the Content Types Supported by a Device

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As noted in the Retrieving the Functional Categories Supported by a Device topic, Windows Portable Devices may support one or more functional categories. Any given functional category may support one or more content types. For example, the storage category may support content types of folder, audio, and image.

For a description of the content types supported by WPD, see the WPD_CONTENT_TYPE_ALL topic.

The ListSupportedContentTypes function in the DeviceCapabilities.cpp module demonstrates the retrieval of content types for the functional categories supported by a selected device.

Your application can retrieve the functional categories supported by a device using the interfaces described in the following table.

Interface Description
IPortableDeviceCapabilities Interface Provides access to the functional-category retrieval methods.
IPortableDevicePropVariantCollection Interface Used to enumerate and store functional-category data.

 

The code found in the ListSupportedContentTypes function is almost identical to the code found in the ListFunctionalCategories function. (See the Retrieving Functional Categories Supported by a Device topic.) The one difference is the call to the IPortableDeviceCapabilities::GetSupportedContentTypes method, which appears within the loop that iterates through the functional categories.

HRESULT hr = S_OK;
CComPtr<IPortableDeviceCapabilities>            pCapabilities;
CComPtr<IPortableDevicePropVariantCollection>   pCategories;
DWORD dwNumCategories   = 0;

if (pDevice == NULL)
{
    printf("! A NULL IPortableDevice interface pointer was received\n");
    return;
}

// Get an IPortableDeviceCapabilities interface from the IPortableDevice interface to
// access the device capabilities-specific methods.
hr = pDevice->Capabilities(&pCapabilities);
if (FAILED(hr))
{
    printf("! Failed to get IPortableDeviceCapabilities from IPortableDevice, hr = 0x%lx\n",hr);
}

// Get all functional categories supported by the device.
// We will use these categories to enumerate functional objects
// that fall within them.
if (SUCCEEDED(hr))
{
    hr = pCapabilities->GetFunctionalCategories(&pCategories);
    if (FAILED(hr))
    {
        printf("! Failed to get functional categories from the device, hr = 0x%lx\n",hr);
    }
}

// Get the number of functional categories found on the device.
if (SUCCEEDED(hr))
{
    hr = pCategories->GetCount(&dwNumCategories);
    if (FAILED(hr))
    {
        printf("! Failed to get number of functional categories, hr = 0x%lx\n",hr);
    }
}

printf("\n%d Functional Categories Found on the device\n\n", dwNumCategories);

// Loop through each functional category and display its name and supported content types.
if (SUCCEEDED(hr))
{
    for (DWORD dwIndex = 0; dwIndex < dwNumCategories; dwIndex++)
    {
        PROPVARIANT pv = {0};
        PropVariantInit(&pv);
        hr = pCategories->GetAt(dwIndex, &pv);
        if (SUCCEEDED(hr))
        {
            // We have a functional category.  It is assumed that
            // functional categories are returned as VT_CLSID
            // VarTypes.

            if ((pv.puuid != NULL)      &&
                (pv.vt    == VT_CLSID))
            {
                // Display the functional category name
                printf("Functional Category: ");
                DisplayFunctionalCategory(*pv.puuid);
                printf("\n");

                // Display the content types supported for this category
                CComPtr<IPortableDevicePropVariantCollection> pContentTypes;
                hr = pCapabilities->GetSupportedContentTypes(*pv.puuid, &pContentTypes);
                if (SUCCEEDED(hr))
                {
                    printf("Supported Content Types: ");
                    DisplayContentTypes(pContentTypes);
                    printf("\n\n");
                }
                else
                {
                    printf("! Failed to get supported content types from the device, hr = 0x%lx\n",hr);
                }
            }
            else
            {
                printf("! Invalid functional category found\n");
            }
        }

        PropVariantClear(&pv);
    }
}

IPortableDevice Interface

IPortableDeviceCapabilities Interface

IPortableDevicePropVariantCollection Interface

Programming Guide