How to translate a HTREEITEM or TVITEM to a Nodes collection index

[MKuiper]

Situation :
- a VB app which contains a treeview (mscomctl.ocx) on a form
- a C++ dll which is subclassing the treeview

When the C++ dll receives a message, like TVM_SELECTITEM, it receives a HTREEITEM which identifies the node.
I can get a TVITEM structure of the node at this point, that gives me additional information, including the lParam field, which seems to be unique for each node.

I need the subclass to call ocx-methods on the node. This requires me to know the key or index of the node in the Nodes collection.
Her is the problem, I can't figure out how to get the key or index of the node from the HTREEITEM or lParam.

Any help greatly appreciated,

Marcel

 

[MKuiper]

Got it.

DWORD ptr = (DWORD)GlobalLock ( (HGLOBAL)lParam );
if ( ptr != 0 )
{ ptr += 88; // Seems to be on offset 88 of some structure
IDispatch * pNode = (IDispatch *)ptr;
// pNode is a pointer to the Node object of interest
//
// do something with the node
//
GlobalUnlock ( (HGLOBAL)lParam ); }

Marcel

 

[dEVooXiAm]

If there is no direct access struct available, imagen MS "improving" the data stored in lParam.. Yes - your code is gonna go BOOM this way of "hacking" is about "use at your own risk", so you better be looking for a function to retrieve the IDispatch from a node. If it's not there, then it is not meant to be, and therefore can be removed, moved or changed any time. Just a notice, gl

------------------
When you do it, do it right.

 

[MKuiper]

You're right, but I must take the risk unless somebody comes up with something better. Fortunately it seems quite unlikely that Microsoft is going to improve mscomctl.ocx sooner or later.

Marcel