Firefox 4 beta 8 -> get_accChild() returns E_INVALIDARG

Hi all,

This code was OK on beta 6, but fails on beta 8 (not tested on beta
7). This code simply tries to get the first child of an object:

hr=AccessibleObjectFromWindow(w,(DWORD)OBJID_CLIENT,IID_IAccessible,
(void**)&pTopAccessible);
hr=pTopAccessible->accNavigate(0x1009,vtStart,&vtResult); //
NAVRELATION_EMBEDS = 0x1009
pIDispatch=(IDispatch*)vtResult.lVal;
hr=pIDispatch->QueryInterface(IID_IAccessible, (void**)&pAccessible);
hr=pAccessible->get_accChildCount(&lCount);
//  ==> value of lCount is 6 in my example
vtChild.vt=VT_I4;
vtChild.lVal=1;
hr=pAccessible->get_accChild(vtChild,&pIDispatch); => hr=S_OK
...
vtChild.lVal=6;
hr=pAccessible->get_accChild(vtChild,&pIDispatch); => hr=E_INVALIDARG!

Do you have an idea? Not sure, but I guess there is a bug in the
Firefox code: I suppose there is a test like this in the
get_accChild() method:
if (vtChild.lVal >= lCount) return E_INVALIDARG; // where lCount is
the number of childs.
As the childs are 1 based and not 0 based, the right code should be:
if (vtChild.lVal > lCount) return E_INVALIDARG; // where lCount is the
number of childs.

Thanks!

Sylvain