[RESOLVED] Printer status: detecting on or off

[Ellis Dee]

In my shutdown program -- which defrags the harddrive with Diskeeper Lite, scans for spyware with AdAware and then scans for viruses with AVG before powering down -- I want it to warn me if I left the printer on.

Searching for existing threads uncovered this post, which links to this article. But that article is poorly constructed; it doesn't offer functional code.

Can anyone help me piece it together? This is what I have so far:

Option Explicit

Public Enum Printer_Status
    PRINTER_STATUS_READY = &H0
    PRINTER_STATUS_PAUSED = &H1
    PRINTER_STATUS_ERROR = &H2
    PRINTER_STATUS_PENDING_DELETION = &H4
    PRINTER_STATUS_PAPER_JAM = &H8
    PRINTER_STATUS_PAPER_OUT = &H10
    PRINTER_STATUS_MANUAL_FEED = &H20
    PRINTER_STATUS_PAPER_PROBLEM = &H40
    PRINTER_STATUS_OFFLINE = &H80
    PRINTER_STATUS_IO_ACTIVE = &H100
    PRINTER_STATUS_BUSY = &H200
    PRINTER_STATUS_PRINTING = &H400
    PRINTER_STATUS_OUTPUT_BIN_FULL = &H800
    PRINTER_STATUS_NOT_AVAILABLE = &H1000
    PRINTER_STATUS_WAITING = &H2000
    PRINTER_STATUS_PROCESSING = &H4000
    PRINTER_STATUS_INITIALIZING = &H8000
    PRINTER_STATUS_WARMING_UP = &H10000
    PRINTER_STATUS_TONER_LOW = &H20000
    PRINTER_STATUS_NO_TONER = &H40000
    PRINTER_STATUS_PAGE_PUNT = &H80000
    PRINTER_STATUS_USER_INTERVENTION = &H100000
    PRINTER_STATUS_OUT_OF_MEMORY = &H200000
    PRINTER_STATUS_DOOR_OPEN = &H400000
    PRINTER_STATUS_SERVER_UNKNOWN = &H800000
    PRINTER_STATUS_POWER_SAVE = &H1000000
End Enum

Private Type PRINTER_INFO_2
    pServerName As String
    pPrinterName As String
    pShareName As String
    pPortName As String
    pDriverName As String
    pComment As String
    pLocation As String
    pDevMode As Long
    pSepFile As String
    pPrintProcessor As String
    pDatatype As String
    pParameters As String
    pSecurityDescriptor As Long
    Attributes As Long
    Priority As Long
    DefaultPriority As Long
    StartTime As Long
    UntilTime As Long
    Status As Long
    JobsCount As Long
    AveragePPM As Long
End Type

Private Const CCHDEVICENAME = 32
Private Const CCHFORMNAME = 32

Private 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
    dmUnusedPadding As Integer
    dmBitsPerPel As Long
    dmPelsWidth As Long
    dmPelsHeight As Long
    dmDisplayFlags As Long
    dmDisplayFrequency As Long
End Type

Private Type PRINTER_DEFAULTS
    pDatatype As String
    pDevMode As DEVMODE
    DesiredAccess As Long
End Type

Private Declare Function ClosePrinter Lib "winspool.drv" (ByVal hPrinter As Long) As Long
Private Declare Function GetPrinterApi Lib "winspool.drv" Alias "GetPrinterA" (ByVal hPrinter As Long, ByVal Level As Long, buffer As Long, ByVal pbSize As Long, pbSizeNeeded As Long) As Long
Private Declare Function OpenPrinter Lib "winspool.drv" Alias "OpenPrinterA" (ByVal pPrinterName As String, phPrinter As Long, pDefault As PRINTER_DEFAULTS) As Long


Private Sub Command1_Click()
    Dim lret As Long
    Dim pDef As PRINTER_DEFAULTS
    Dim mhPrinter As Long
    Dim Index As Long
    
    lret = OpenPrinter(Printer.DeviceName, mhPrinter, pDef)
    
    Dim SizeNeeded As Long
    
    Dim buffer() As Long
    
    ReDim Preserve buffer(0 To 1) As Long
    lret = GetPrinterApi(mhPrinter, Index, buffer(0), UBound(buffer), SizeNeeded)
    ReDim Preserve buffer(0 To (SizeNeeded / 4) + 3) As Long
    lret = GetPrinterApi(mhPrinter, Index, buffer(0), UBound(buffer) * 4, SizeNeeded)

Dim mPRINTER_INFO_2 As PRINTER_INFO_2
With mPRINTER_INFO_2 '\\ This variable is of type PRINTER_INFO_2
   .pServerName = StringFromPointer(buffer(0), 1024)
   .pPrinterName = StringFromPointer(buffer(1), 1024)
   .pShareName = StringFromPointer(buffer(2), 1024)
   .pPortName = StringFromPointer(buffer(3), 1024)
   .pDriverName = StringFromPointer(buffer(4), 1024)
   .pComment = StringFromPointer(buffer(5), 1024)
   .pLocation = StringFromPointer(buffer(6), 1024)
   .pDevMode = buffer(7)
   .pSepFile = StringFromPointer(buffer(8), 1024)
   .pPrintProcessor = StringFromPointer(buffer(9), 1024)
   .pDatatype = StringFromPointer(buffer(10), 1024)
   .pParameters = StringFromPointer(buffer(11), 1024)
   .pSecurityDescriptor = buffer(12)
   .Attributes = buffer(13)
   .Priority = buffer(14)
   .DefaultPriority = buffer(15)
   .StartTime = buffer(16)
   .UntilTime = buffer(17)
   .Status = buffer(18)
   .JobsCount = buffer(19)
   .AveragePPM = buffer(20)
End With
ClosePrinter mhPrinter
End Sub

Public Function StringFromPointer(lpString As Long, lMaxLength As Long) As String

  Dim sRet As String
  Dim lret As Long

  If lpString = 0 Then
    StringFromPointer = ""
    Exit Function
  End If

  If IsBadStringPtrByLong(lpString, lMaxLength) Then
    '\\ An error has occured - do not attempt to use this pointer
      StringFromPointer = ""
    Exit Function
  End If

  '\\ Pre-initialise the return string...
  sRet = Space$(lMaxLength)
  CopyMemory ByVal sRet, ByVal lpString, ByVal Len(sRet)
  If Err.LastDllError = 0 Then
    If InStr(sRet, Chr$(0)) > 0 Then
      sRet = Left$(sRet, InStr(sRet, Chr$(0)) - 1)
    End If
  End If

  StringFromPointer = sRet

End Function

[Ellis Dee]

Drat, I was able to get the holes filled by using a post from here, but the code doesn't tell me whether the printer is on or off. Sure, there is an enumerated value for PRINTER_STATUS_OFFLINE, but it never returns that. When the printer is powered off, the printer status from the above code is set to PRINTER_STATUS_READY.

So back to square one. Anyone know how to do this? All I want is to be able to throw up a msgbox saying "Turn off the printer, dummy!" before beginning the shutdown process, but only if the printer is actually on.

[Ellis Dee]

Googling turned up much shorter code that actually works, which I have adapted into a generic utility function:

Public Function PrinterOffline(Optional pstrPrinter As String = "Default") As Boolean
    Dim strWhere As String
    Dim objWMI As Object
    Dim objPrinters As Object
    Dim objPrinter As Object
    
    Set objWMI = GetObject("winmgmts:\\.\root\CIMV2")
    If LCase$(pstrPrinter) = "default" Then
        strWhere = "Default = True"
    Else
        strWhere = "Name = '" & pstrPrinter & "'"
    End If
    Set objPrinters = objWMI.ExecQuery("SELECT * FROM Win32_Printer WHERE " & strWhere)
    For Each objPrinter In objPrinters
        PrinterOffline = objPrinter.WorkOffline
        Exit For
    Next
    Set objPrinter = Nothing
    Set objPrinters = Nothing
    Set objWMI = Nothing
End Function

Send this function the name of the printer you want to query, or send it nothing to query the default printer. Returns True if the printer is turned off or not ready, False if the printer is on.

Does anyone know how I can remove the For...Each loop from the code? It strike me as quite inelegant.

[si_the_geek]

Presumably the For loop would be equivalent to this:

        PrinterOffline = objPrinters(1).WorkOffline

[Ellis Dee]

Nope, both of the following...

objPrinters(0).WorkOffline
objPrinters(1).WorkOffline

...generate "Generic Failure" errors, whatever the heck that means.

[Ellis Dee]

If you run that code and add a breakpoint to Watch objPrinters, it shows the sub-object of objPrinters to be named "Item 1", with a space. What the heck?

And of course, like virtually everything else I've tried...

objPrinters.Item(1).WorkOffline

...raises a "Generic Failure" error.

[si_the_geek]

That is the normal way a collection is shown in the watch window.

By a process of elimination I have found that objPrinters.Item(x) and just objPrinters(x) are both correct - but I can't get past the "Generic Failure" either, which is rather odd as the "For Each" does basically the same thing.

[Merri]

For some reason I see nothing hard in this:

Public Function IsPrinterOff(Optional Printer As String) As Boolean
    Dim strWhere As String
    If LenB(Printer) Then
        strWhere = "Name = '" & Replace(Printer, "'", "\'") & "'"
    Else
        strWhere = "Default = TRUE"
    End If
    IsPrinterOff = GetObject("winmgmts:\\.\root\CIMV2").ExecQuery("SELECT * FROM Win32_Printer WHERE " & strWhere & " AND WorkOffline = TRUE").Count
End Function

You can even modify it to see if any printer is turned on. Just change the WQL.

Public Function PrintersOn() As Long
    Dim strWQL As String
    strWQL = "SELECT * FROM Win32_Printer WHERE WorkOffline = FALSE"
    PrintersOn = GetObject("winmgmts:\\.\root\CIMV2").ExecQuery(strWQL).Count
End Function

[Merri]

si_the_geek: enumeration (For Each) is provided by an entirely different mechanism than the regular Item interface. You may want to search and look at SelfEnum or ObjectCollection that I posted at some point, it shows you what is required to create the For Each mechanism "manually".

[si_the_geek]

That makes sense I guess.. thanks for easing my confusion!

[Merri]

I also found this resource that should make it much easier to understand WMI: Windows 2000 Scripting Guide

One of the interesting parts is how it tells you how to get a single object instead of getting all of them, by using Get instead of ExecQuery (I didn't try it yet, but I assume many of those are true for printers as well).

[Merri]

Here is how you can get the status of the first printer installed in the system:

Public Function Test() As Boolean
    Test = GetObject("winmgmts:\\.\root\CIMV2").Get("Win32_Printer='" & Printers(0).DeviceName & "'").WorkOffline
End Function

Private Sub Form_Load()
    MsgBox Test
End Sub

Yeah, it makes use of VB's Printers collection


Basically that Get would be the same you'd give to Item of the collection returned, but why get the collection if you can get single item this way as well... so you only want to use ExecQuery with For Each and nothing else.

[Ellis Dee]

Thanks, Merri!