How to detect if a given PIDL is actually a .zip file or similar?

Question

VS2010 introduced CMFCShellTreeCtrl which allows for a folder-browser tree ctrl to be dropped into our MFC apps.

However, there seems to be a serious lack of filtering capabilities in this class. i.e. it will build the list of container-objects (IShellFolder). But there doesn't seem to be a way to specify that .zip containers should not be displayed in the folder tree.

It does supply a virtual that could be used crudely for this purpose:

HRESULT CMFCShellTreeCtrl::EnumObjects(HTREEITEM hParentItem, LPSHELLFOLDER pParentFolder, LPITEMIDLIST pidlParent)
{
  ASSERT_VALID(this);
  ASSERT_VALID(afxShellManager);

  LPENUMIDLIST pEnum = NULL;

  HRESULT hr = pParentFolder->EnumObjects(NULL, m_dwFlags, &pEnum);
  if (FAILED(hr) || pEnum == NULL)
  {
      return hr;
  }

  LPITEMIDLIST pidlTemp;
  DWORD dwFetched = 1;

  // Enumerate the item's PIDLs:
  while (SUCCEEDED(pEnum->Next(1, &pidlTemp, &dwFetched)) && dwFetched)
  {
      TVITEM tvItem;
      ZeroMemory(&tvItem, sizeof(tvItem));

      // Fill in the TV_ITEM structure for this item:
      tvItem.mask = TVIF_PARAM | TVIF_TEXT | TVIF_IMAGE | TVIF_SELECTEDIMAGE | TVIF_CHILDREN;

      // AddRef the parent folder so it's pointer stays valid:
      pParentFolder->AddRef();

      // Put the private information in the lParam:
      LPAFX_SHELLITEMINFO pItem = (LPAFX_SHELLITEMINFO)GlobalAlloc(GPTR, sizeof(AFX_SHELLITEMINFO));
      ENSURE(pItem != NULL);

      pItem->pidlRel = pidlTemp;
      pItem->pidlFQ = afxShellManager->ConcatenateItem(pidlParent, pidlTemp);

      pItem->pParentFolder = pParentFolder;
      tvItem.lParam = (LPARAM)pItem;

      CString strItem = OnGetItemText(pItem);
      tvItem.pszText = strItem.GetBuffer(strItem.GetLength());
      tvItem.iImage = OnGetItemIcon(pItem, FALSE);
      tvItem.iSelectedImage = OnGetItemIcon(pItem, TRUE);

      // Determine if the item has children:
      DWORD dwAttribs = SFGAO_HASSUBFOLDER | SFGAO_FOLDER | SFGAO_DISPLAYATTRMASK | SFGAO_CANRENAME | SFGAO_FILESYSANCESTOR;

      pParentFolder->GetAttributesOf(1, (LPCITEMIDLIST*) &pidlTemp, &dwAttribs);
      tvItem.cChildren = (dwAttribs & (SFGAO_HASSUBFOLDER | SFGAO_FILESYSANCESTOR));

      // Determine if the item is shared:
      if (dwAttribs & SFGAO_SHARE)
      {
          tvItem.mask |= TVIF_STATE;
          tvItem.stateMask |= TVIS_OVERLAYMASK;
          tvItem.state |= INDEXTOOVERLAYMASK(1); //1 is the index for the shared overlay image
      }

      // Fill in the TV_INSERTSTRUCT structure for this item:
      TVINSERTSTRUCT tvInsert;

      tvInsert.item = tvItem;
      tvInsert.hInsertAfter = TVI_LAST;
      tvInsert.hParent = hParentItem;

      InsertItem(&tvInsert);
      dwFetched = 0;
  }

  pEnum->Release();
  return S_OK;
}

What I am confused by is the lack of ability to distinguish what type of object this is that is being enumerated (or a better way to control the enumeration in the first place so as to filter out non-filesystem objects such as these).

It's possible to look at the text for the item being enumerated, and simply exclude it if it ends in ".zip". However, this seems wonky to me. After all, an arbitrary folder could be named XYZ.zip (which still being a folder, and not a zip archive). Similarly, there are likely other archive types than just .zip that may be yet supported in the future - or other container types which are nevertheless not really folders.

I don't want to eliminate things like "Network" and "Computer" from being valid nodes. Just ones that are problematic such as "Downloads\Foobar.zip"

I apologize for this question being rambling. Any help in improving my understanding and creative approaches to knowing what sorts of objects are part of Microsoft's shell namespace, and how that they can be gainfully used would be appreciated!

Answer 1

A zip file/folder would have SFGAO_STREAM/SFGAO_DROPTARGET along with SFGAO_FOLDER, so if you can read the shell item as stream, then it probably isn't a directory. Another way to tell is to use SHGetPathFromIDList+PathIsDirectory, however this only works for pidl that have file system paths.

There are other kind of browsable files too, like a saved search (and if you browse into the file it takes like forever to finish enumerating the items), so you probably want to think about how to deal with those files too.