IAccessible::get_accHelp method (oleacc.h)

Artykuł
07/27/2022

The IAccessible::get_accHelp method retrieves the Help property string of an object. Not all objects support this property.

Syntax

HRESULT get_accHelp(
  [in]          VARIANT varChild,
  [out, retval] BSTR    *pszHelp
);

Parameters

[in] varChild

Type: VARIANT

Specifies whether the retrieved help information belongs to the object or one of the object's child elements. This parameter is either CHILDID_SELF (to obtain information about the object) or a child ID (to obtain information about one of the object's child elements). For more information about initializing the VARIANT, see How Child IDs Are Used in Parameters.

[out, retval] pszHelp

Type: BSTR*

Address of a BSTR that receives the localized string containing the help information for the specified object, or NULL if no help information is available.

Return value

Type: HRESULT

If successful, returns S_OK.

If not successful, returns one of the values in the table that follows, or another standard COM error code. Servers return these values, but clients must always check output parameters to ensure that they contain valid values. For more information, see Checking IAccessible Return Values.

Error	Description
S_FALSE	No help information is available.
E_INVALIDARG	An argument is not valid.
DISP_E_MEMBERNOTFOUND	The object does not support this property.

Remarks

None of the predefined and common controls support this property.

Note to server developers: Localize the string returned from this property.

This property returns a string, whereas IAccessible::get_accHelpTopic provides access to a Help topic in WinHelp. Objects are not required to support both IAccessible::get_accHelp and IAccessible::get_accHelpTopic, but they must support at least one. If they easily return a string, they must support IAccessible::get_accHelp ; otherwise they must support IAccessible::get_accHelpTopic. If both are supported, IAccessible::get_accHelpTopic provides more detailed information.

Server Example

The following example code shows one possible implementation of this method for a custom list box. Different text is displayed depending on the status of the contact in the list. For simplicity, the example does not localize the returned string.


// m_pControl is the custom control that returns this accessible object. 
// 'online' is an enumerated value. 

HRESULT STDMETHODCALLTYPE AccServer::get_accHelp( 
    VARIANT varChild,
    BSTR *pszHelp)
{
    *pszHelp = NULL;
    if (varChild.vt != VT_I4)
    {
        return E_INVALIDARG;
    }
    if (varChild.lVal == CHILDID_SELF)
    {
        *pszHelp = SysAllocString(L"Contact list.");
    }
    else
    {
        int index = (int)varChild.lVal - 1;
        CustomListControlItem* pItem = m_pControl->GetItemAt(index);
        if (pItem == NULL)
        {
            return E_INVALIDARG;
        }
        if (pItem->GetStatus() == online)
        {
            *pszHelp = SysAllocString(L"Online contact.");
        }
        else 
        {
            *pszHelp = SysAllocString(L"Offline contact.");
        }
    }
    return S_OK;
};

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	oleacc.h
Library	Oleacc.lib
DLL	Oleacc.dll
Redistributable	Active Accessibility 1.3 RDK on Windows NT 4.0 with SP6 and later and Windows 95

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