BUG: Skip() Member Function of the IEnumVARIANT Interface Returns Incorrect Values

ID: Q228504

The information in this article applies to:

Microsoft Win32 Software Development Kit (SDK)

SYMPTOMS

The default implementation of IEnumVARIANT::Skip() for objects created by the Active Accessibility component is incorrect and returns:

S_OK if not at the end of the enumeration

S_FALSE if at the end of the enumeration

These messages are returned regardless of whether it skipped the number requested or not. This is inconsistent with the documented behavior of IEnumVARIANT::Skip() which would only return S_OK if the specified number of elements were skipped.

This problem affects objects created by Oleacc.dll on behalf of system controls and user interface elements and common controls.

STATUS

This behavior is by design.

MORE INFORMATION

The return values of IEnumVARIANT::Skip( unsigned long celt ) are documented as:

S_OK if the number of elements skipped is equal to celt, and
S_FALSE if the number of elements skipped is fewer than celt.

This function is internally called by the AccessibleChildren() function. But the AccessibleChildren() function handles the odd return values and the Skip() function works fine internally. If this function is called externally, which is not recommended, then the oddity in the return value should be noted.

To avoid problems when dealing with IEnumVARIANT, it is recommended that Skip() function is not used and AccessibleChildren() function with a non-zero iChildStart value is not called. Instead, use the AccessibleChildren() with an iChildStart of 0 to get all the children, or use IEnumVARIANT::Next() to retrieve them one by one (or in chunks), and manually skip over the ones that are not needed. VariantClear() must be called to clear the unused variants.

REFERENCES

MSAA

Additional query words: kbAAcc kbWinOS kbNTOS400 kbWinOS2000

Keywords : kbAAcc kbNTOS400 kbWinOS2000 kbWinOS
Version : WINDOWS:
Platform : WINDOWS
Issue type : kbbug