Testing if TreeView's node is checked

I have recently answered a question on Stack Overflow where OP wanted to programmatically determine if TreeView's node is checked or not, among other things. My answer got accepted since everything seems to work fine.

Still, after reading MSDN documentation for TVN_KEYDOWN, I found the part in the "Return value" section that mentioned incremental search. Therefore I have decided to ask what is a proper return value for my usage of that notification and have concluded that I should return a nonzero value.

Question:

My concern is if my code is the best way for testing if the tree's node is checked or not. That is why I came here to ask for review of that code, and for possible suggestions for improving it.

Here is the tree's creation in WM_CREATE handler:

case WM_CREATE:
    {
        // this is your treeview

        TreeView = CreateWindowEx(0, WC_TREEVIEW, 
            TEXT("Tree View"), WS_VISIBLE | WS_CHILD, 
            0, 0, 200, 500, 
            hwnd, (HMENU)ID_TREE_VIEW, GetModuleHandle(NULL), NULL);

        /************ enable checkboxes **************/

        DWORD dwStyle = GetWindowLong( TreeView , GWL_STYLE);
        dwStyle |= TVS_CHECKBOXES;
        SetWindowLongPtr( TreeView , GWL_STYLE, dwStyle );

       /************ add items and subitems **********/

        // add root item

        TVINSERTSTRUCT tvis = {0};

        tvis.item.mask = TVIF_TEXT;
        tvis.item.pszText = L"This is root item";
        tvis.hInsertAfter = TVI_LAST;
        tvis.hParent = TVI_ROOT;

        HTREEITEM hRootItem = reinterpret_cast<HTREEITEM>( SendMessage( TreeView , 
            TVM_INSERTITEM, 0, reinterpret_cast<LPARAM>( &tvis ) ) );

        // add firts subitem for the hTreeItem

        memset( &tvis, 0, sizeof(TVINSERTSTRUCT) );

        tvis.item.mask = TVIF_TEXT;
        tvis.item.pszText = L"This is first subitem";
        tvis.hInsertAfter = TVI_LAST;
        tvis.hParent = hRootItem;

        HTREEITEM hTreeSubItem1 = reinterpret_cast<HTREEITEM>( SendMessage( TreeView , 
            TVM_INSERTITEM, 0, reinterpret_cast<LPARAM>( &tvis ) ) );

        // now we insert second subitem for hRootItem

        memset( &tvis, 0, sizeof(TVINSERTSTRUCT) );

        tvis.item.mask = TVIF_TEXT | TVIF_STATE; // added extra flag
        tvis.item.pszText = L"This is second subitem";
        tvis.hInsertAfter = TVI_LAST;
        tvis.hParent = hRootItem;

        // for demonstration purposes let us check this node;
        // to do that add the following code, and add the extra flag for 
        // mask member like above
        tvis.item.stateMask = TVIS_STATEIMAGEMASK;
        tvis.item.state = 2 << 12;

        HTREEITEM hTreeSubItem2 = reinterpret_cast<HTREEITEM>( SendMessage( TreeView , 
            TVM_INSERTITEM, 0, reinterpret_cast<LPARAM>( &tvis ) ) );

        // let us expand the root node so we can see if checked state is really set
        TreeView_Expand( TreeView, hRootItem, TVE_EXPAND );
    }
    return 0L;

Here is the WM_NOTIFY handler that determines if tree is checked or not:

case WM_NOTIFY:
    {
        LPNMHDR lpnmh = (LPNMHDR) lParam;

        if( lpnmh->idFrom == ID_TREE_VIEW  )  // if this is our treeview control
        {
            switch( lpnmh->code )  // let us filter notifications
            {
            case TVN_KEYDOWN:  // tree has keyboard focus and user pressed a key
                {

                    LPNMTVKEYDOWN ptvkd = (LPNMTVKEYDOWN)lParam; 

                    if( ptvkd->wVKey == VK_SPACE )  // if user pressed spacebar
                    {

                        // get the currently selected item
                        HTREEITEM ht = TreeView_GetSelection( ptvkd->hdr.hwndFrom );

                        // Prepare to test items state

                        TVITEM tvItem;

                        tvItem.mask = TVIF_HANDLE | TVIF_STATE;
                        tvItem.hItem = (HTREEITEM)ht;
                        tvItem.stateMask = TVIS_STATEIMAGEMASK;

                        // Request the information.
                        TreeView_GetItem( ptvkd->hdr.hwndFrom, &tvItem );

                        // Return zero if it's not checked, or nonzero otherwise.
                        if( (BOOL)(tvItem.state >> 12) - 1 )
                            MessageBox( hwnd, L"Not checked!", L"", MB_OK );
                        else
                            MessageBox( hwnd, L"Checked!", L"", MB_OK );

                    }
                }
                return 0L;  // see the documentation for TVN_KEYDOWN

            case NM_CLICK:  // user clicked on a tree
                {
                    TVHITTESTINFO ht = {0};

                    DWORD dwpos = GetMessagePos();

                    // include <windowsx.h> and <windows.h> header files
                    ht.pt.x = GET_X_LPARAM(dwpos);
                    ht.pt.y = GET_Y_LPARAM(dwpos);
                    MapWindowPoints( HWND_DESKTOP, lpnmh->hwndFrom, &ht.pt, 1 );

                    TreeView_HitTest(lpnmh->hwndFrom, &ht);

                    if(TVHT_ONITEMSTATEICON & ht.flags)
                    {
                        // Prepare to receive the desired information.

                        TVITEM tvItem;

                        tvItem.mask = TVIF_HANDLE | TVIF_STATE;
                        tvItem.hItem = (HTREEITEM)ht.hItem;
                        tvItem.stateMask = TVIS_STATEIMAGEMASK;

                        // Request the information.
                        TreeView_GetItem( lpnmh->hwndFrom, &tvItem );

                        // Return zero if it's not checked, or nonzero otherwise.
                        if( (BOOL)(tvItem.state >> 12) - 1 )
                            MessageBox( hwnd, L"Not checked!", L"", MB_OK );
                        else
                            MessageBox( hwnd, L"Checked!", L"", MB_OK );

                    }
                }
            default:
                break;
        }
    }
}
break;