Does This HTREEITEM Belong To This TreeView Control?

Question

Does This HTREEITEM Belong To This TreeView Control?

a_unique_name 401

Hello Folks:

Developing on Win 10 Pro, Visual Studio 2022 Version 17.9.4 ( updated yesterday), C++, Win32 no MFC.

TL,DR: Is there a way to see if an HTREEITEM belongs to a TreeView?

My treeview's customdraw notification is being passed an HTREEITEM that makes no sense, 0xCCCCCCCC.

The code attempts to use this HTREEITEM in a SendMessage(..., TVM_GETITEM, ..., ...) to the TreeView and the program fails spectacularly. It consistently fails in the code I use to subclass the TreeView control.

I have a lot of work to do in order to find the cause of the problem, but I'm wondering if there is a safe way to see if a HTREEITEM belongs to a TreeView.

Thanks

Larry

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Answer 1

Viorel 122.6K

If it is always 0xCCCCCCCC, use if(item == (HTREEITEM)0xCCCCCCCC).... Or try this helper function:

bool IsValid( HWND tree, HTREEITEM item, HTREEITEM parent = NULL )
{
    HTREEITEM t = (HTREEITEM)SendMessage( tree, TVM_GETNEXTITEM, parent == NULL ? TVGN_ROOT : TVGN_CHILD, (LPARAM)parent );

    for( ; t != NULL;)
    {
        if( t == item ) return true;
        if( IsValid( tree, item, t ) ) return true;

        t = (HTREEITEM)SendMessage( tree, TVM_GETNEXTITEM, TVGN_NEXT, (LPARAM)t );
    }

    return false;
}

The call IsValid( tree, (HTREEITEM)0xCCCCCCCC ) should return false.

a_unique_name 401 Reputation points

2024-03-30T17:43:56.2766667+00:00

Thanks Again Viorel:

That works.

Larry

Answer 2

RLWA32 49,636

In debug builds the VC++ compiler will store sentinel values in uninitialized variables. Variables allocated on the heap are filled with 0xCD and stack variables are filled with 0xCC.

If your HTREEITEM variable contains 0xCCCCCCCC that would indicate that you are working with an uninitialized variable that is an invalid HTREEITEM.

a_unique_name 401 Reputation points

2024-03-31T23:17:44.9066667+00:00

Thanks Again RLWA32:

I've seen 0xCCCCCCCC many times before, I didn't realize, when debugging, it specifically marks uninitialized memory.

Larry

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Does This HTREEITEM Belong To This TreeView Control?

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