IRawElementProviderSimple::GetPropertyValue method (uiautomationcore.h)

Retrieves the value of a property supported by the Microsoft UI Automation provider.

Syntax

HRESULT GetPropertyValue(
  [in]          PROPERTYID propertyId,
  [out, retval] VARIANT    *pRetVal
);

Parameters

[in] propertyId

Type: PROPERTYID

The property identifier. For a list of property IDs, see Property Identifiers.

[out, retval] pRetVal

Type: VARIANT*

Receives the property value, or VT_EMPTY if the property is not supported by this provider. This parameter is passed uninitialized. See Remarks.

Return value

Type: HRESULT

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

If the provider does not support the propertyId property, the provider should set pRetVal->vt to VT_EMPTY and return S_OK.

Remarks

If a provider is explicitly hiding the property value (that is, the provider does not supply the property, and the request is not to be passed through to other providers), it should return a pointer obtained by using the UiaGetReservedNotSupportedValue function. For example:

pRetVal->vt = VT_UNKNOWN;
UiaGetReservedNotSupportedValue(&pRetVal->punkVal);

UI Automation properties of the double type support Not a Number (NaN) values. When returning a NaN value, the provider should return a quiet (non-signaling) NaN to avoid raising an exception if floating-point exceptions are turned on. The following example shows how to create a quiet NaN:

ULONGLONG ulNaN = 0xFFFFFFFFFFFFFFFF;
    *pRetVal = *reinterpret_cast<double*>(&ulNaN);

Alternatively, you can use the following function from the standard C++ libraries:

numeric_limits<double>::quiet_NaN( )

Examples

The following example returns various property values. The UiaIds structure contains property identifiers; to see how it is initialized, see UiaLookupId.

HRESULT STDMETHODCALLTYPE Provider::GetPropertyValue(PROPERTYID propertyId, 
        VARIANT* pRetVal)
{
    if (propertyId == UiaIds.ControlTypeProperty)
    {
        pRetVal->vt = VT_I4;
        pRetVal->lVal = UiaIds.ButtonControlType;
    }

    // The Name property normally comes from the Caption property of the 
    // control window, if it has one. The Name is overridden here for the 
    // sake of illustration. 
    else if (propertyId == UiaIds.NameProperty)
    {
        pRetVal->vt = VT_BSTR;
        pRetVal->bstrVal = SysAllocString(L"ColorButton");
    }
    else
    {
        pRetVal->vt = VT_EMPTY;
        // UI Automation will attempt to get the property from the host 
        //window provider.
    }
    return S_OK;
}
            

Requirements

See also

IRawElementProviderSimple