Wrong PIDL got from CIDA when dragging a Control Panel item

I'm working on a drag and drop problem now and trying to get the PIDLs of the items being dragged from windows shell to my application.

The code below can get correct PIDLs if the dragged item is 'My Computer' or 'Control Panel' itself, but it doesn't work when the dragged item is an item in the 'Control Panel'.

What's wrong with my code?

#define GetPIDLFolder(pida) (LPCITEMIDLIST)(((LPBYTE)pida)+(pida)->aoffset[0])
#define GetPIDLItem(pida, i) (LPCITEMIDLIST)(((LPBYTE)pida)+(pida)->aoffset[i+1])

STGMEDIUM medium;

UINT fmt = RegisterClipboardFormat(CFSTR_SHELLIDLIST);
FORMATETC fe= {fmt, NULL, DVASPECT_CONTENT, -1, TYMED_HGLOBAL};
HRESULT GETDATA_RESULT = pDataObject->GetData(&fe, &medium);

if (SUCCEEDED(GETDATA_RESULT))
{
    LPIDA pida = (LPIDA)GlobalLock(medium.hGlobal);
    LPCITEMIDLIST pidlFolder = GetPIDLFolder(pida);

    int n = pida->cidl;  // the n is always correct
    if( n > 0 )
    {
        LPCITEMIDLIST pidlItem = GetPIDLItem(pida, 0);
        // the pidlItem is wrong when the dragged object is an item in 'Control Panel'
    }

    GlobalUnlock(medium.hGlobal);
}
ReleaseStgMedium(&medium);

Any idea? Thanks

Zach@Shine

If I D&D Mouse, Network Connections and Fonts I get the following output in my test app:

• 0 Mouse | sfgao=4 hr=0
• 1 ::{20D04FE0-3AEA-1069-A2D8-08002B30309D}\::{21EC2020-3AEA-1069-A2DD-08002B30309D}\::{7007ACC7-3202-11D1-AAD2-00805FC1270E} | sfgao=20000004 hr=0
• 2 C:\WINDOWS\Fonts | sfgao=60000004 hr=0

The Network Connections and Fonts pidls can be converted to fully qualified shell paths while Mouse only returns a relative path/displayname. This makes sense if you check the documentation for IShellFolder::GetDisplayNameOf:

...They do not guarantee that IShellFolder will return the requested form of the name. If that form is not available, a different one might be returned. In particular, there is no guarantee that the name returned by the SHGDN_FORPARSING flag will be successfully parsed by IShellFolder::ParseDisplayName. There are also some combinations of flags that might cause the GetDisplayNameOf/ParseDisplayName round trip to not return the original identifier list. This occurrence is exceptional, but you should check to be sure.

It is clear that when dealing with controlpanel items, you need to keep the pidl around and only use GetDisplayNameOf for display strings in your UI. (IShellLink::SetIDList on the Mouse pidl will create a working shortcut so the pidl is valid)

void OnDrop(IDataObject*pDO) 
{
    STGMEDIUM medium;
    UINT fmt = RegisterClipboardFormat(CFSTR_SHELLIDLIST);
    FORMATETC fe= {fmt, NULL, DVASPECT_CONTENT, -1, TYMED_HGLOBAL};
    HRESULT hr = pDO->GetData(&fe, &medium);
    if (SUCCEEDED(hr)) 
    {
        LPIDA pida = (LPIDA)GlobalLock(medium.hGlobal);
        if (pida) 
        {
            LPCITEMIDLIST pidlFolder = GetPIDLFolder(pida);
            for (UINT i=0; i<pida->cidl; ++i) 
            {
                LPCITEMIDLIST pidlItem = GetPIDLItem(pida,i);
                LPITEMIDLIST pidlAbsolute = ILCombine(pidlFolder,pidlItem);
                if (pidlAbsolute) 
                {
                    IShellFolder*pParentSF;
                    hr= SHBindToParent(pidlAbsolute,IID_IShellFolder,(void**)&pParentSF,&pidlItem);
                    if (SUCCEEDED(hr))
                    {
                        STRRET str; 
                        hr= pParentSF->GetDisplayNameOf(pidlItem, SHGDN_FORPARSING, &str);
                        if (SUCCEEDED(hr))
                        {
                            TCHAR szName[MAX_PATH];
                            hr= StrRetToBuf(&str,pidlItem,szName,MAX_PATH);
                            if (SUCCEEDED(hr)) 
                            {
                                SFGAOF sfgao = SFGAO_FOLDER|SFGAO_FILESYSTEM|SFGAO_HASSUBFOLDER|SFGAO_CANLINK;
                                hr= pParentSF->GetAttributesOf(1,&pidlItem,&sfgao);
                                TRACE(_T("%u %s | sfgao=%X hr=%X\n"),i,szName,sfgao,hr);
                                CreateTestShortcut(pidlAbsolute);
                            }
                        }
                        pParentSF->Release();
                    }
                    ILFree(pidlAbsolute);
                }
            }
            GlobalUnlock(medium.hGlobal);
        }
        ReleaseStgMedium(&medium);
    }
}