Binaryworld - How to set default printer programatically on Win 9x/NT ? ... [ VB -> Printing ]

This article shows how to programmatically set which printer is the system default printer. Not all applications or components can select a specific printer to use. This often makes it necessary to change the default printer for the system so that the application or component will use the desired printer.

The following code sample provides a means to determine which printers are available, and to designate one as the system default printer.

Step-by-Step Example

- Start a new Standard EXE project in Visual Basic. Form1 is created by default.
- Add a new module to the project and insert the following code:

Module1.bas

Click here to copy the following block

Public Const HWND_BROADCAST = &HFFFF
Public Const WM_WININICHANGE = &H1A

' constants for DEVMODE structure
Public Const CCHDEVICENAME = 32
Public Const CCHFORMNAME = 32

' constants for DesiredAccess member of PRINTER_DEFAULTS
Public Const STANDARD_RIGHTS_REQUIRED = &HF0000
Public Const PRINTER_ACCESS_ADMINISTER = &H4
Public Const PRINTER_ACCESS_USE = &H8
Public Const PRINTER_ALL_ACCESS = (STANDARD_RIGHTS_REQUIRED Or _
    PRINTER_ACCESS_ADMINISTER Or PRINTER_ACCESS_USE)

' constant that goes into PRINTER_INFO_5 Attributes member
' to set it as default
Public Const PRINTER_ATTRIBUTE_DEFAULT = 4

' Constant for OSVERSIONINFO.dwPlatformId
Public Const VER_PLATFORM_WIN32_WINDOWS = 1

Public Type OSVERSIONINFO
  dwOSVersionInfoSize As Long
  dwMajorVersion As Long
  dwMinorVersion As Long
  dwBuildNumber As Long
  dwPlatformId As Long
  szCSDVersion As String * 128
End Type

Public Type DEVMODE
  dmDeviceName As String * CCHDEVICENAME
  dmSpecVersion As Integer
  dmDriverVersion As Integer
  dmSize As Integer
  dmDriverExtra As Integer
  dmFields As Long
  dmOrientation As Integer
  dmPaperSize As Integer
  dmPaperLength As Integer
  dmPaperWidth As Integer
  dmScale As Integer
  dmCopies As Integer
  dmDefaultSource As Integer
  dmPrintQuality As Integer
  dmColor As Integer
  dmDuplex As Integer
  dmYResolution As Integer
  dmTTOption As Integer
  dmCollate As Integer
  dmFormName As String * CCHFORMNAME
  dmLogPixels As Integer
  dmBitsPerPel As Long
  dmPelsWidth As Long
  dmPelsHeight As Long
  dmDisplayFlags As Long
  dmDisplayFrequency As Long
  dmICMMethod As Long   ' // Windows 95 only
  dmICMIntent As Long   ' // Windows 95 only
  dmMediaType As Long   ' // Windows 95 only
  dmDitherType As Long   ' // Windows 95 only
  dmReserved1 As Long   ' // Windows 95 only
  dmReserved2 As Long   ' // Windows 95 only
End Type

Public Type PRINTER_INFO_5
  pPrinterName As String
  pPortName As String
  Attributes As Long
  DeviceNotSelectedTimeout As Long
  TransmissionRetryTimeout As Long
End Type

Public Type PRINTER_DEFAULTS
  pDatatype As Long
  pDevMode As Long
  DesiredAccess As Long
End Type

Declare Function GetProfileString Lib "kernel32" _
    Alias "GetProfileStringA" _
    (ByVal lpAppName As String, _
    ByVal lpKeyName As String, _
    ByVal lpDefault As String, _
    ByVal lpReturnedString As String, _
    ByVal nSize As Long) As Long

Declare Function WriteProfileString Lib "kernel32" _
    Alias "WriteProfileStringA" _
    (ByVal lpszSection As String, _
    ByVal lpszKeyName As String, _
    ByVal lpszString As String) As Long

Declare Function SendMessage Lib "user32" _
    Alias "SendMessageA" _
    (ByVal hwnd As Long, _
    ByVal wMsg As Long, _
    ByVal wParam As Long, _
    lparam As String) As Long

Declare Function GetVersionExA Lib "kernel32" _
    (lpVersionInformation As OSVERSIONINFO) As Integer

Public Declare Function OpenPrinter Lib "winspool.drv" _
    Alias "OpenPrinterA" _
    (ByVal pPrinterName As String, _
    phPrinter As Long, _
    pDefault As PRINTER_DEFAULTS) As Long

Public Declare Function SetPrinter Lib "winspool.drv" _
    Alias "SetPrinterA" _
    (ByVal hPrinter As Long, _
    ByVal Level As Long, _
    pPrinter As Any, _
    ByVal Command As Long) As Long

Public Declare Function GetPrinter Lib "winspool.drv" _
    Alias "GetPrinterA" _
    (ByVal hPrinter As Long, _
    ByVal Level As Long, _
    pPrinter As Any, _
    ByVal cbBuf As Long, _
    pcbNeeded As Long) As Long

Public Declare Function lstrcpy Lib "kernel32" _
    Alias "lstrcpyA" _
    (ByVal lpString1 As String, _
    ByVal lpString2 As Any) As Long

Public Declare Function ClosePrinter Lib "winspool.drv" _
    (ByVal hPrinter As Long) As Long

Public Sub SelectPrinter(NewPrinter As String)
  Dim Prt As Printer

  For Each Prt In Printers
    If Prt.DeviceName = NewPrinter Then
      Set Printer = Prt
      Exit For
    End If
  Next
End Sub

- Place a ListBox and a CommandButton on Form1.
- Add the following code to the General Declarations section of Form1:

Form1.frm

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Option Explicit

Private Function PtrCtoVbString(Add As Long) As String
  Dim sTemp As String * 512, x As Long

  x = lstrcpy(sTemp, Add)
  If (InStr(1, sTemp, Chr(0)) = 0) Then
    PtrCtoVbString = ""
  Else
    PtrCtoVbString = Left(sTemp, InStr(1, sTemp, Chr(0)) - 1)
  End If
End Function

Private Sub SetDefaultPrinter(ByVal PrinterName As String, _
  ByVal DriverName As String, ByVal PrinterPort As String)
  Dim DeviceLine As String
  Dim r As Long
  Dim l As Long
  DeviceLine = PrinterName & "," & DriverName & "," & PrinterPort
  ' Store the new printer information in the [WINDOWS] section of
  ' the WIN.INI file for the DEVICE= item
  r = WriteProfileString("windows", "Device", DeviceLine)
  ' Cause all applications to reload the INI file:
  l = SendMessage(HWND_BROADCAST, WM_WININICHANGE, 0, "windows")
End Sub

Private Sub Win95SetDefaultPrinter()
  Dim Handle As Long    'handle to printer
  Dim PrinterName As String
  Dim pd As PRINTER_DEFAULTS
  Dim x As Long
  Dim need As Long     ' bytes needed
  Dim pi5 As PRINTER_INFO_5 ' your PRINTER_INFO structure
  Dim LastError As Long

  ' determine which printer was selected
  PrinterName = List1.List(List1.ListIndex)
  ' none - exit
  If PrinterName = "" Then
    Exit Sub
  End If

  ' set the PRINTER_DEFAULTS members
  pd.pDatatype = 0&
  pd.DesiredAccess = PRINTER_ALL_ACCESS Or pd.DesiredAccess

  ' Get a handle to the printer
  x = OpenPrinter(PrinterName, Handle, pd)
  ' failed the open
  If x = False Then
    'error handler code goes here
    Exit Sub
  End If

  ' Make an initial call to GetPrinter, requesting Level 5
  ' (PRINTER_INFO_5) information, to determine how many bytes
  ' you need
  x = GetPrinter(Handle, 5, ByVal 0&, 0, need)
  ' don't want to check Err.LastDllError here - it's supposed
  ' to fail
  ' with a 122 - ERROR_INSUFFICIENT_BUFFER
  ' redim t as large as you need
  ReDim t((need \ 4)) As Long

  ' and call GetPrinter for keepers this time
  x = GetPrinter(Handle, 5, t(0), need, need)
  ' failed the GetPrinter
  If x = False Then
    'error handler code goes here
    Exit Sub
  End If

  ' set the members of the pi5 structure for use with SetPrinter.
  ' PtrCtoVbString copies the memory pointed at by the two string
  ' pointers contained in the t() array into a Visual Basic string.
  ' The other three elements are just DWORDS (long integers) and
  ' don't require any conversion
  pi5.pPrinterName = PtrCtoVbString(t(0))
  pi5.pPortName = PtrCtoVbString(t(1))
  pi5.Attributes = t(2)
  pi5.DeviceNotSelectedTimeout = t(3)
  pi5.TransmissionRetryTimeout = t(4)

  ' this is the critical flag that makes it the default printer
  pi5.Attributes = PRINTER_ATTRIBUTE_DEFAULT

  ' call SetPrinter to set it
  x = SetPrinter(Handle, 5, pi5, 0)

  If x = False Then    ' SetPrinter failed
    MsgBox "SetPrinter Failed. Error code: " & Err.LastDllError
    Exit Sub
  Else
    If Printer.DeviceName <> List1.Text Then
      ' Make sure Printer object is set to the new printer
      SelectPrinter (List1.Text)
    End If
  End If

  ' and close the handle
  ClosePrinter (Handle)
End Sub

Private Sub GetDriverAndPort(ByVal Buffer As String, DriverName As _
  String, PrinterPort As String)

  Dim iDriver As Integer
  Dim iPort As Integer
  DriverName = ""
  PrinterPort = ""

  ' The driver name is first in the string terminated by a comma
  iDriver = InStr(Buffer, ",")
  If iDriver > 0 Then

    ' Strip out the driver name
    DriverName = Left(Buffer, iDriver - 1)

    ' The port name is the second entry after the driver name
    ' separated by commas.
    iPort = InStr(iDriver + 1, Buffer, ",")

    If iPort > 0 Then
      ' Strip out the port name
      PrinterPort = Mid(Buffer, iDriver + 1, _
          iPort - iDriver - 1)
    End If
  End If
End Sub

Private Sub ParseList(lstCtl As Control, ByVal Buffer As String)
  Dim i As Integer
  Dim s As String

  Do
    i = InStr(Buffer, Chr(0))
    If i > 0 Then
      s = Left(Buffer, i - 1)
      If Len(Trim(s)) Then lstCtl.AddItem s
      Buffer = Mid(Buffer, i + 1)
    Else
      If Len(Trim(Buffer)) Then lstCtl.AddItem Buffer
      Buffer = ""
    End If
  Loop While i > 0
End Sub

Private Sub WinNTSetDefaultPrinter()
  Dim Buffer As String
  Dim DeviceName As String
  Dim DriverName As String
  Dim PrinterPort As String
  Dim PrinterName As String
  Dim r As Long
  If List1.ListIndex > -1 Then
    ' Get the printer information for the currently selected
    ' printer in the list. The information is taken from the
    ' WIN.INI file.
    Buffer = Space(1024)
    PrinterName = List1.Text
    r = GetProfileString("PrinterPorts", PrinterName, "", _
        Buffer, Len(Buffer))

    ' Parse the driver name and port name out of the buffer
    GetDriverAndPort Buffer, DriverName, PrinterPort

    If DriverName <> "" And PrinterPort <> "" Then
      SetDefaultPrinter List1.Text, DriverName, PrinterPort
      If Printer.DeviceName <> List1.Text Then
        ' Make sure Printer object is set to the new printer
        SelectPrinter (List1.Text)
      End If
    End If
   End If
End Sub

Private Sub Command1_Click()
    Dim osinfo As OSVERSIONINFO
    Dim retvalue As Integer

    osinfo.dwOSVersionInfoSize = 148
    osinfo.szCSDVersion = Space$(128)
    retvalue = GetVersionExA(osinfo)

    If osinfo.dwPlatformId = VER_PLATFORM_WIN32_WINDOWS Then
      Call Win95SetDefaultPrinter
    Else
      ' This assumes that future versions of Windows use the NT method
      Call WinNTSetDefaultPrinter
    End If
  End Sub

Private Sub Form_Load()
    Dim r As Long
    Dim Buffer As String
    Command1.Caption = "<< Set as Default Printer"
    ' Get the list of available printers from WIN.INI
    Buffer = Space(8192)
    r = GetProfileString("PrinterPorts", vbNullString, "", _
        Buffer, Len(Buffer))

    ' Display the list of printer in the ListBox List1
    ParseList List1, Buffer
End Sub

- Run the project and note that the preceding code populates a ListBox with all available printers.
- Select one printer in the list and make it the default by clicking the CommandButton.
- Confirm that the default printer has changed: On the Start button, select Settings, select Printers, and then check which printer is marked as the default. Alternatively, you can print to the default printer from any application on your system.