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Class for Browsing shell namespace with your own dialog
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<p>This article was contributed by <A HREF="mailto:sofori@chat.carleton.ca">Selom Ofori (a.k.a SubRosa)</A>.
<p><img src="browse_shell_namespace1.gif" tppabs="http://www.codeguru.com/dialog/browse_shell_namespace1.gif"></p>
<p><img src="browse_shell_namespace2.gif" tppabs="http://www.codeguru.com/dialog/browse_shell_namespace2.gif"></p>
<p>CShellTree Version 1.02 (any previous unversioned copies are older/inferior). Please
see <a href="http://chat.carleton.ca/%7esofori">http://chat.carleton.ca/~sofori</a> for
updates and method descriptions. Thanks to everybody who reported/fixed some of the
bugs and to those who requested features.
<p>Created with MSVC 5, tested under Win95 OSR2 and WinNT 4
<br>
<P>Anybody who is interested in having a ShellFolder tree directly in his or her
dialog box has probably tried to come to grips with MFCENUM. MFCENUM is pretty
easy to understand, but only if you go through the pain of trying to modify the code
to work with yours. CShellTree contains the important parts of MFCENUM that deals with
browsing the shell namespace.
<P>CShellTree which inherits CTreeCtrl. After you initialize the tree with the Shell Folders
the only other interaction the Shell 'engine' has with the tree control is through TVN_ITEMEXPANDING
(when the user clicks on the plus sign or double clicks on the folder).
<P>Operations:
<PRE><TT><FONT COLOR="#990000"> // Initializes the treeview with "mycomputer" etc
void PopulateTree();
// Initializes the treeview starting with a special folder as root
// See the SHGetSpecialFolderLocation() for constants and descriptions
void PopulateTree(int SpecialFolderID);
// Must be called from OnItemExpanding(), message TVN_ITEMEXPANDING
void OnFolderExpanding(NMHDR* pNMHDR, LRESULT* pResult);
// Frees memory allocated for the shell object. message TVN_DELETEITEM
void OnDeleteShellItem(NMHDR* pNMHDR, LRESULT* pResult);
// Must be called from OnRclick(). message NM_RCLICK
void GetContextMenu(NMHDR* pNMHDR, LRESULT* pResult);
// Must be called from OnSelChanged(), message TVN_SELCHANGED
BOOL OnFolderSelected(NMHDR* pNMHDR, LRESULT* pResult, CString &szFolderPath);
// Enables Folder Images in the tree control.
void EnableImages();
// Retrieves the path of the Selected Folder.
BOOL GetSelectedFolderPath(CString &szFolderPath);
// Opens the folder of the specified path. Does it's own error checking
void TunnelTree(CString szFindPath)
</FONT></TT></PRE>
<P>The General Steps are:
<ol>
<li>Include 'shelltree.cpp' and 'shelltree.h' into your project<br>
Include 'shellpidl.cpp' and 'shellpidl.h' into your project<br>
Include 'filename.cpp' and 'filename.h' into your project<br>
<PRE><TT><FONT COLOR="#990000"> #include "Shelltree.h"
#include "shellpidl.h"
#include "filename.h"
</FONT></TT></PRE>
<li> Create a dialog or use an existing dialog (after you are familar with CShellTree)</li><br><br>
<li> Add a treecontrol to your dialog.
<PRE><TT><FONT COLOR="#990000">
CShellTree* m_TreeCtl;
</FONT></TT></PRE>
<p>Do not create member variables of the treecontrol using classwizard. Instead open the header
file of the dialog class.
<br><br>
<li>In your OnInitDialog(), a callback to the WM_INITDIALOG message, initialize your treecontrol
<PRE><TT><FONT COLOR="#990000">BOOL CTreeSelect::OnInitDialog()
{
CDialog::OnInitDialog();
// TODO: Add extra initialization here
m_TreeCtl = (CShellTree*) GetDlgItem(IDC_SHELLTREE); //replace IDC_SHELLTREE with your control's ID
ASSERT(m_TreeCtl);
m_TreeCtl->EnableImages(); //enable images
m_TreeCtl->PopulateTree(); //populate for the with Shell Folders for the first time
return TRUE; // return TRUE unless you set the focus to a control
// EXCEPTION: OCX Property Pages should return FALSE
}
</FONT></TT></PRE>
<P><b>NOTE:</b> REQUIRED. CShellTree handles the images for you. DO NOT attach an ImageList to CSHellTree. This internal imagelist
is a handle to the system image list and uses it directly. Using CImageList will result in the
system imagelist being destroyed after your application exits.
<P>The call
<PRE><TT><FONT COLOR="#990000"> m_TreeCtl->EnableImages();
</FONT></TT></PRE>
creates and attaches an image list to the Tree Control
<P>To initialize the ShellFolders you call
<PRE><TT><FONT COLOR="#990000"> m_TreeCtl->PopulateTree();
</FONT></TT></PRE>
<P>This fills it with the starting folders like "My Computer","network neighbourhood etc"</li><br><br>
<li>It is very important that you create OnItemExpanding(), a callback to TVN_ITEMEXPANDING.
Otherwise your shell would be pretty much dead.
<PRE><TT><FONT COLOR="#990000">void CTreeSelect::OnItemexpanding(NMHDR* pNMHDR, LRESULT* pResult)
{
NM_TREEVIEW* pNMTreeView = (NM_TREEVIEW*)pNMHDR;
// TODO: Add your control notification handler code here
m_TreeCtl->FolderExpanding(pNMHDR,pResult);
*pResult = 0;
}
</FONT></TT></PRE>
<P><b>Comments:</b> REQUIRED. The FolderExpanding() method of CShellTree does the dirty work of
adding folder nodes to the tree control. It takes the same paramters as your
OnItemExpanding, so all you have to do is pass the paramters along.
</li><br><br>
<li> If you want a popup menu to be active, create a OnRclick(), a callback to NM_RCLICK. This
popup is the same as the one in windows explorer.
<PRE><TT><FONT COLOR="#990000">void CTreeSelect::OnRclick(NMHDR* pNMHDR, LRESULT* pResult)
{
// TODO: Add your control notification handler code here
m_TreeCtl->FolderPopup(pNMHDR,pResult);
*pResult = 0;
}
</FONT></TT></PRE>
<P><b>Comments:</b> Takes the same paramters as OnRclick. All you do is pass on the parameters to
the FolderPopup() method of CShellTree. The popup is handled by the system.
</li><br><br>
<li> CShellTree expects you to keep track of the filepath in your OnSelChanged(), a callback to
TVN_SELCHANGED. CShellTree provides a method
<PRE><TT><FONT COLOR="#990000"> FolderSelected(NMHDR* pNMHDR, LRESULT* pResult, CString &szFolderPath)
</FONT></TT></PRE>
<P> intended to by called from your OnSelChanged() callback function. The CString object will contain
the path of that folder selected if FolderSelected() returns TRUE. If it returns FALSE, the
node selected isn't part of the filesystem and has no path.
<P><b>Comments:</b> Use this function if you need to set the path in a corresponding combobox or editwindow.
<PRE><TT><FONT COLOR="#990000">void CTreeSelect::OnSelchanged(NMHDR* pNMHDR, LRESULT* pResult)
{
NM_TREEVIEW* pNMTreeView = (NM_TREEVIEW*)pNMHDR;
// TODO: Add your control notification handler code here
CString SelPath;
if(m_TreeCtl->FolderSelected(pNMHDR,pResult,SelPath))
MessageBox(SelPath);
*pResult = 0;
}
</FONT></TT></PRE>
<P><b>Comments:</b> The above code displays the path of the Folder selected if it's in the filesystem.
</li><br><br>
<li>You must allow CShellTree to release the memory allocated for the Shellobjects. in your
OnDeleteItem(), a callback to TVN_DELETEITEM, CShellTree provides a method
<PRE><TT><FONT COLOR="#990000"> void OnDeleteShellItem(NMHDR* pNMHDR, LRESULT* pResult);
</FONT></TT></PRE>
<p>You absolutely <b>must</b> call this method or your project will leak memory
<PRE><TT><FONT COLOR="#990000">void CTreeExampleDlg::OnDeleteitem(NMHDR* pNMHDR, LRESULT* pResult)
{
NM_TREEVIEW* pNMTreeView = (NM_TREEVIEW*)pNMHDR;
// TODO: Add your control notification handler code here
m_TreeCtl->OnDeleteShellItem(pNMHDR,pResult);
*pResult = 0;
}
</FONT></TT></PRE>
</ol>
<h4>MISC NOTES:</h4>
<ol>
<li>void CShellTree::TunnelTree(CString szFindPath) requires that you
implement the TVN_SELCHANGED message handler. TunnelTree will just
just not work if you do NOT implement it. Works only on folders under
"MY COMPUTER". This means local drives and mapped network drives. No
network neighbourhood or whatever
<li>void CShellTree::PopulateTree(int nSpecialFolder) will start the tree at
a special folder location. See ::ShBrowseForFolder() and ::ShGetSpecialFolderLocation().
CShellTree::TunnelTree() will not work if you use this method to initialize the tree.
</ol>
<P>BONUS: You can get the path of the Selected Node by calling GetSelectedFolderPath(). It will
return TRUE if the selected Folder is part of the filesystem. Returns false if an item
hasn't been selected or the Folder is not part of the filesystem. eg. "My Computer"
<h4>HISTORY:</h4>
v1.02
<ul>
<li>Fixed a skipped initialization of a variable that caused TunnelTree() to crash on WinNT
if the folder didn't have any subfolders
<li>Added TunnelTree(CString szFindPath) and PopulateTree(int SpecialFolder) methods
<li>Implemented a required call to OnDeleteShellItem(); TVN_DELETEITEM, that released the memory
allocated by that shell folder
</ul>
<P><A HREF="browse_shell_namespace_src.zip" tppabs="http://www.codeguru.com/dialog/browse_shell_namespace_src.zip">Download source files</A>
<P><A HREF="browse_shell_namespace_proj.zip" tppabs="http://www.codeguru.com/dialog/browse_shell_namespace_proj.zip">Download project files</A>
<p>Last updated 6 April 1998
<P>
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