Option Explicit

Private Const MaxMRU = 4  'Maximum number of MRUs in list (-1 for no limit)
Private Const NotFound = -1   'Indicates a duplicate entry was not found
Private Const NoMRUs = -1     'Indicates no MRUs are currently defined

Private MRUCount As Long      'Maintains a count of MRUs defined

Private Sub Form_Load()
   ' Initialize the count of MRUs
   MRUCount = NoMRUs
   
   ' Call sub to retrieve the MRU filenames
   GetMRUFileList
End Sub

Private Sub Form_Unload(Cancel As Integer)
   ' Call sub to save the MRU filenames
   SaveMRUFileList
End Sub

Private Sub mnuMRU_Click(Index As Integer)
   ' Call sub to reorder the MRU list
   ReorderMRUList mnuMRU(Index).Caption, CLng(Index)
End Sub

Private Sub mnuOpen_Click()
   ' Show the file open common dialog
   Me.CommonDialog1.ShowOpen
   
   ' Call sub to add this file as an MRU
   AddMRUItem Me.CommonDialog1.FileName
End Sub

Private Sub AddMRUItem(NewItem As String)
   Dim result As Long
      
   ' Call sub to check for duplicates
   result = CheckForDuplicateMRU(NewItem)
   
   ' Handle case if duplicate found
   If result <> NotFound Then
      ' Call sub to reorder MRU list
      ReorderMRUList NewItem, result
   Else
      ' Call sub to add new item to MRU menu
      AddMenuElement NewItem
   End If
End Sub

Private Function CheckForDuplicateMRU(ByVal NewItem As String) As Long
   Dim i As Long
   
   ' Uppercase newitem for string comparisons
   NewItem = UCase$(NewItem)
   
   ' Check all existing MRUs for duplicate
   For i = 0 To MRUCount
      If UCase$(Me.mnuMRU(i).Caption) = NewItem Then
         ' Duplicate found, return the location of the duplicate
         CheckForDuplicateMRU = i
         
         ' Stop searching
         Exit Function
      End If
   Next i
   
   ' No duplicate found, so return -1
   CheckForDuplicateMRU = -1
End Function

Private Sub mnuQuit_Click()
   ' Close the program
   Unload Me
End Sub

Private Sub AddMenuElement(NewItem As String)
   Dim i As Long
   
   ' Check that we will not exceed maximum MRUs
   If (MRUCount < (MaxMRU - 1)) Or (MaxMRU = -1) Then
      'Increment the menu count
      MRUCount = MRUCount + 1
      
      ' Check if this is the first item
      If MRUCount <> 0 Then
         ' Add a new element to the menu
         Load mnuMRU(MRUCount)
      End If
      
      ' Make new element visible
      mnuMRU(MRUCount).Visible = True
   End If
   
   ' Shift items to maintain most recent to least recent
   For i = (MRUCount) To 1 Step -1
      ' Set the captions
      mnuMRU(i).Caption = mnuMRU(i - 1).Caption
   Next i
   
   ' Set caption for new item
   mnuMRU(0).Caption = NewItem
End Sub

Private Sub ReorderMRUList(DuplicateMRU As String, DuplicateLocation As Long)
   Dim i As Long
   
   ' Move entries previously "more recent" than the
   ' duplicate down one in the MRU list
   For i = DuplicateLocation To 1 Step -1
      mnuMRU(i).Caption = mnuMRU(i - 1).Caption
   Next i
   
   ' Set caption of newitem
   mnuMRU(0).Caption = DuplicateMRU
End Sub

Private Sub GetMRUFileList()
   Dim i As Long           'Loop control variable
   Dim result As String    'Name of MRU from registry
   
   ' Loop through all entries
   Do
      ' Retrieve entry from registry
      result = GetSetting(App.Title, "MRUFiles", Trim$(CStr(i)), "")
      
      ' Check if a value was returned
      If result <> "" Then
         ' Call sub to additem to MRU list
         AddMRUItem result
      End If
      
      ' Increment counter
      i = i + 1
   Loop Until (result = "")
End Sub

Private Sub SaveMRUFileList()
   Dim i As Long           ' Loop control variable
   
   ' Loop through all MRU
   For i = 0 To MRUCount
      ' Write MRU to registry with key as it's position in list
      SaveSetting App.Title, "MRUFiles", Trim$(CStr(i)), mnuMRU(i).Caption
   Next i
End Sub