Introduction
The Shell API function SHBrowseForFolder displays a dialog box that enables the user to select a Shell folder. The dialog box allows the user to select any folder because its root folder is Desktop (which contains My Documents, My Computer and My Network Places). Some applications need to restrict the user in the selection of folders. Restricting the selection for My Computer or My Network Places is easier. But restricting the user for a particular folder requires little manipulation.
Background
The function SHBrowseForFolder takes a pointer to the structure BROWSEINFO. This structure has eight members. One of the members, pidlRoot, is a pointer to the structure ITEMIDLIST. If pidlRoot is NULL, the root folder is Desktop. One can use pre-defined CSIDL values such as CSIDL_MYDOCUMENTS, CSIDL_NETWORK, etc. If any other arbitrary folder is to be used as root folder, it should be appropriately converted to the structure ITEMIDLIST.
The class CFoldersDialog puts the whole code for SHBrowseForFolder dialog. The function ConvertPathToLpItemIdList converts an arbitrary folder into ITEMIDLIST. This class can be used in MFC as well as SDK without making any changes. It can also be used in VC++.NET.
The function ConvertPathToLpItemIdList takes an arbitrary folder as string type input parameter. It first converts the string to OLECHAR. Then SHGetDesktopFolder function retrieves IShellFolder interface and calls the method ParseDisplayName. This method puts the OLECHAR form of root folder into ITEMIDLIST structure.
Using the Code
The function BrowseFolder is called from any other class by creating an object of CFoldersDialog. It first uses the function ConvertPathToLpItemIdList for converting string to ITEMIDLIST and then use its callback function BrowseCallbackProc.
LPITEMIDLIST ConvertPathToLpItemIdList(const char *pszPath)
{
LPITEMIDLIST pidl = NULL;
LPSHELLFOLDER pDesktopFolder = NULL;
OLECHAR olePath[MAX_PATH];
ULONG chEaten;
HRESULT hr;
if (SUCCEEDED(SHGetDesktopFolder(&pDesktopFolder)))
{
MultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, pszPath, -1,
olePath, MAX_PATH);
hr = pDesktopFolder->ParseDisplayName(NULL, NULL,
olePath, &chEaten, &pidl, NULL);
pDesktopFolder->Release();
return pidl;
}
return NULL;
}
int CALLBACK BrowseCallbackProc(HWND hwnd, UINT uMsg, LPARAM lp, LPARAM pData)
{
switch(uMsg)
{
case BFFM_SELCHANGED:
{
if (SHGetPathFromIDList((LPITEMIDLIST) lp, szDir))
SendMessage(hwnd,BFFM_SETSTATUSTEXT, 0, (LPARAM)szDir);
break;
}
case BFFM_INITIALIZED:
{
SendMessage(hwnd, BFFM_SETSELECTION, 1,(LPARAM) szDir);
}
break;
default:
break;
}
return 0;
}
int CFoldersDialog::BrowseFolder(HWND hWnd, CString RootPath)
{
BROWSEINFO bi;
TCHAR szDir[MAX_PATH];
LPITEMIDLIST pidl;
LPMALLOC pMalloc;
int nRet = 0;
if (SUCCEEDED(SHGetMalloc(&pMalloc)))
{
ZeroMemory(&bi,sizeof(bi));
bi.hwndOwner = hWnd;
bi.pszDisplayName = 0;
bi.lpszTitle = 0;
char *pszRootPath = new char[RootPath.GetLength() + 1];
wcstombs(pszRootPath, RootPath, RootPath.GetLength());
bi.pidlRoot = ConvertPathToLpItemIdList(pszRootPath);
if (bi.pidlRoot == NULL)
nRet = 1;
bi.ulFlags = BIF_RETURNONLYFSDIRS | BIF_STATUSTEXT;
bi.lpfn = BrowseCallbackProc;
pidl = SHBrowseForFolder(&bi);
if (pidl)
SHGetPathFromIDList(pidl,szDir);
else
nRet = 2;
pMalloc->Free(pidl);
pMalloc->Release();
}
return nRet;
}
Points of Interest
The callback function displays the user selected subfolder at the top of the dialog. Once the user click the OK button, the folder value is transferred to the second text box in the first dialog box. The variable szDir is accessed from both CFoldersDialog and the calling class.
History
- First version 1.0: April 27, 2003
- Second version 2.0: February 22, 2010
- Fixed bugs
- Added Unicode support
- Compiled demo project with Visual Studio 6, 2005, 2008 and 2010
