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**Lance Edmonds** · 5 Jul 2001, 08:01 PM

The callback is needed to verify that the dialog should highlight the specified initial folder... exactly as you noted. Without the start folder confirmation (Sending a %bffm_setselection message), the dialog will start with the default set to "My Computer" (or whatever it haappens to be called on the particular installation).

This is "briefly" documented in WIN32.HLP.

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

**Mike Trader** · 5 Jul 2001, 10:28 PM

Thx Lance,

I found Win32.hlp at: http://www.cs.virginia.edu/~lcc-win32/

I read it, but i just dont get why its necessary to send a message to the main hDlg window?

The Win32.hlp says:
The browse dialog box calls this function to notify it about events.

notify IT - I assume the IT is the SHBROWSEFORFOLDER Dialog box.

So why are we sending a message to the HDlg window? There is nothing in that Callback function to process anything?
What is accomplished by doing that?

------------------
Kind Regards
Mike

**Lance Edmonds** · 6 Jul 2001, 03:39 AM

The callback in your code is a simple callback rather than a DlgProc/WndProc callback, per se.

That is, it is not the callback that processes every single SHBrowseForFolder dialog event. Rather, it is a user-defined callback that can receive/process a limited number of notifications from the SHBrowseForFolder dialog - events that your app may need to operate upon for some reason.

For example, in one of my apps, I use the callback to verify whether the selected folder name is valid in the scope of my application, and if not, I send a %BFFM_ENABLEOK message to disable the OK button. See my very recent post for a snapshot of my callback which (tries to) prevent non-local folder names from being selected.

A couple of tips for you:

1. All references to 256 bytes should be replaced with the equate %MAX_PATH (which is 260).

2. In the calling code, you need to free the memory used by the ID List after retrieving the folder name:

Code:

DECLARE SUB CoTaskMemFree LIB "ole32.dll" ALIAS "CoTaskMemFree" (BYVAL hMem AS LONG)
...
IF lpidlist& THEN        
  ' zBuffer = SPACE$(%MAX_PATH) ' ASCIIZ strings do not need to be pre-initialized!
  CALL SHGETPATHFROMIDLIST (lpidlist&, zBuffer)
  CoTaskMemFree lpidlist&
  FUNCTION = lpidlist
END IF

(Note: in your calling code, your call to SHGetPathFromIDList passes a variable called "Dir", but this should be "zBuffer")

3. In your callback, you are passing an ASCIIZ string to ShGetPathFromIDList, so you can pass the second parameter directly, rather than the BYVAL VARPTR(zDir) method you are using:

Code:

IF SHGETPATHFROMIDLIST(a&, zdir) THEN

4. Since this callback uses the standard format of a WndProc/DlgProc (hWnd,wMsg,wParam,lParam), you can substitute a DDT CALLBACK FUNCTION and use the internal CBxxx system variables. This is purely optional, but makes the code slightly easier to write:

Code:

CALLBACK FUNCTION fbrowseproc
    DIM zdir AS ASCIIZ * %max_path
    IF CBMSG = %BFFM_INITIALIZED THEN
        DIALOG SEND CBHNDL, %BFFM_SETSELECTION, %TRUE, CBLPARAM
    ELSEIF CBMSG = %BFFM_SELCHANGED THEN
        CALL SHGetPathFromIDList(BYVAL CBWPARAM, zDir)
    END IF
END FUNCTION

I hope this helps!

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

**Semen Matusovski** · 6 Jul 2001, 06:15 AM

Mike I combined some fragments.

Code:

   #Compile Exe
   #Register None
   #Dim All
   #Include "WIN32API.INC"

   %ID_FRAME1    = 101
   %ID_DIRECTORY = 102
   %ID_SELECTDIR = 103

   Declare Sub CoTaskMemFree Lib "ole32.dll" Alias "CoTaskMemFree" (pv As Long)
   
   %BIF_RETURNONLYFSDIRS   = 1
   %BIF_STATUSTEXT         = 4
   %BFFM_INITIALIZED       = 1
   %BFFM_SELCHANGED        = 2
   %BFFM_SETSTATUSTEXT     = %WM_USER + 100
   %BFFM_ENABLEOK          = %WM_USER + 101
   %BFFM_SETSELECTION      = %WM_USER + 102
                                    
   CallBack Function BrowseForFolderProc
      Dim TmpAsciiz As Asciiz * %MAX_PATH, StatusText As String, CurDrv As Asciiz * 3
      %maxNetResources = 1000
      Dim i As Long, hEnum As Long, d As Long, j As Long, k As Long
      Dim NetResources(%maxNetResources -1) As NETRESOURCE

      Select Case CbMsg
         Case %BFFM_INITIALIZED
            TmpAsciiz = CurDir$
            SendMessage CbHndl, %BFFM_SETSELECTION, 1, VarPtr(TmpAsciiz)
         Case %BFFM_SELCHANGED
            SHGetPathFromIDList ByVal CbWparam, TmpAsciiz
            StatusText = TmpAsciiz
            
            If Asc(TmpAsciiz, 2) <> 58 Then i = 0 Else i = Asc(TmpAsciiz, 1)
            If i < 65 Or i > 80 Then i = 0 Else If i >= 97 Or i > 112 Then i = i - 32
            
            If i Then
               CurDrv = Chr$(i) + ":"
               Select Case GetDriveType(CurDrv)
                  Case %DRIVE_FIXED
                  Case %DRIVE_REMOTE
                     If IsFalse(WNetOpenEnum(%RESOURCE_CONNECTED, %RESOURCETYPE_ANY, 0&, ByVal 0&, hEnum)) Then
                        If hEnum Then
                           d = %maxNetResources: j = Len(NETRESOURCE) * d
                           If IsFalse(WNetEnumResource(hEnum, d, NetResources(0), j)) Then
                              For k = 0 To d - 1
                                 If UCase$(Left$(NetResources(k)[email protected], 2)) = CurDrv Then _
                                    StatusText = CurDrv + " = " + NetResources(k)[email protected] + " (not allowed)": i = 0
                              Next
                           End If
                           WNetCloseEnum hEnum
                        End If
                     End If
                  Case Else
                     i = 0: StatusText = "Illegal drive"
                End Select
            End If
            If i Then If (GetAttr(TmpAsciiz) And %SUBDIR) <> %SUBDIR Then i = 0
            Dialog Send CbHndl, %BFFM_ENABLEOK, 0, Abs(IsTrue(i))
            SendMessage CbHndl, %BFFM_SETSTATUSTEXT, 0, StrPtr(StatusText)
      End Select
   End Function

   CallBack Function DlgProc
      Select Case CbMsg
         Case %WM_INITDIALOG
            Control Add Frame,   CbHndl, %ID_FRAME1, " Folder ", 5, 5, 260, 27
            Control Add TextBox, CbHndl, %ID_DIRECTORY, "", 10, 15, 200, 12
            Control Add Button,  CbHndl, %ID_SELECTDIR, "Browse", 215, 15, 45, 12
         Case %WM_COMMAND
            If CbCtl = %ID_SELECTDIR Then
               Local pidl As Long, sBrowseInfo As BROWSEINFO, TmpAsciiz As Asciiz * %MAX_PATH, DisplayText As Asciiz * 100
               DisplayText = "Select a folder on local hard disk"
               SHGetSpecialFolderLocation CbHndl, 17, ByVal VarPtr(sBrowseInfo.pIDLRoot)
               sBrowseInfo.hWndOwner = CbHndl
               sBrowseInfo.lpfnCallback  = CodePtr(BrowseForFolderProc)
               sBrowseInfo.pszDisplayName = VarPtr(TmpAsciiz)
               sBrowseInfo.lpszTitle = VarPtr(DisplayText)
               sBrowseInfo.ulFlags = %BIF_RETURNONLYFSDIRS Or %BIF_STATUSTEXT
               pidl = SHBrowseForFolder(sBrowseInfo)
               If pidl Then
                  If SHGetPathFromIDList(ByVal pidl, TmpAsciiz) Then Control Set Text CbHndl, %ID_DIRECTORY, TmpAsciiz
                  CoTaskMemFree ByVal pidl
               End If
               CoTaskMemFree ByVal sBrowseInfo.pIDLRoot
                         
            End If
      End Select
   End Function

   Function PbMain
      Dim hDlg As Long
      Dialog New 0, "Test", , , 270, 70, %WS_CAPTION Or %WS_SYSMENU Or %WS_MINIMIZEBOX To hDlg
      Dialog Show Modal hDlg Call DlgProc
   End Function

BTW, one question, not SHBrowseForFolder relative.
How to detect ia printer port connected to another PC ?
Should be somewhere around WNet .., but lazy to search.
Does somebody know ?

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E-MAIL: [email protected]

**Mike Trader** · 6 Jul 2001, 06:40 AM

Wow Semen & Lance,
I have so much to learn!
Thx for those pointers. I have streamlined my code as much as possible
This is about as simple As I can get it I think.
I use the function return to detect a CANCEL by the user
and I pass the selected folder back using the Initial path variable.

I like this cos I can write on line of code to call the function
and check the result for a cancel:
IF FolderDialog(0,"Select a folder", Path) THEN

So here is what I got:

Code:

#COMPILE EXE "FindFldr.exe"
#INCLUDE     "WIN32API.INC" ' Win API definitions

'************************************************************************
' Find Folder Declarations
'************************************************************************
TYPE browseinfo
     hwndowner AS LONG
     pidlroot AS LONG
     pszdisplayname AS ASCIIZ PTR
     lpsztitle AS ASCIIZ PTR
     ulflags AS LONG
     lpfncallback AS LONG
     lparam AS LONG
     iimage AS LONG
END TYPE

%BFFM_SETSELECTION = %wm_user+102 ' must be this value (102)

DECLARE SUB CoTaskMemFree LIB "ole32.dll" ALIAS "CoTaskMemFree" (BYVAL hMem AS LONG)

'************************************************************************
' Find Folder
'************************************************************************
CALLBACK FUNCTION fbrowseproc
    DIM zdir AS ASCIIZ*%max_path
    IF CBMSG = 1 THEN DIALOG SEND CBHNDL, %BFFM_SETSELECTION, %TRUE, CBLPARAM ' %BFFM_INITIALIZED     
    IF CBMSG = 2 THEN CALL SHGETPATHFROMIDLIST(BYVAL CBWPARAM, zDir) ' %BFFM_SELCHANGED
END FUNCTION    

FUNCTION FolderDialog(hwnd AS LONG, title AS STRING, Dir AS ASCIIZ*%max_path ) AS LONG
    LOCAL zbuffer AS ASCIIZ*%max_path 
    LOCAL lpidlist AS LONG
    LOCAL zstartdir AS ASCIIZ*%max_path 
    LOCAL tbi AS browseinfo
    tbi.hwndowner    = hwnd
    tbi.lpsztitle    = STRPTR(title)
    zstartdir        = Dir
    tbi.ulflags      = &h0001 OR &h0002 OR &h0004
    tbi.pidlroot     = 0
    tbi.lpfncallback = CODEPTR(fbrowseproc) ' Select Starting folder
    tbi.lparam       = VARPTR(zstartdir)
    lpidlist         = SHBROWSEFORFOLDER(tbi)
    IF lpidlist THEN
        CALL SHGETPATHFROMIDLIST (lpidlist&, Dir) ' Return the path
        CALL CoTaskMemFree(lpidlist&)
        FUNCTION = 1 ' User choose a Folder (0 if he hits Cancel)
    END IF
END FUNCTION

'************************************************************************
FUNCTION PBMAIN()AS LONG
LOCAL Path AS ASCIIZ*%max_path 

    Path   = "C:\PBDLL60\BIN" ' Starting Directory
    IF FolderDialog(0,"Select a folder", Path) THEN 
        MSGBOX Path
    END IF

END FUNCTION
'************************************************************************

------------------
Kind Regards
Mike

[This message has been edited by Mike Trader (edited July 06, 2001).]

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