Dllcall autoit partially getting results - autoit

Question

I am having problem with the following code in autoit.
it is suppose to list all printers available in my system and the curresponding papernames supported by each printer.
but am getting only the printer names ans series of '0s' which is suppose to be the papernames
#include <Debug.au3>
#include <String.au3>
Const $DC_BINS = 6
Const $DC_BINNAMES = 12
Const $DC_PAPERNAMES = 16
Const $DC_PAPERS = 2
Const $DC_PAPERSIZE = 3
Dim $BinNameList
$objWMIService = ObjGet("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2")
$colInstalledPrinters = $objWMIService.ExecQuery ("Select Name, PortName from Win32_Printer")
For $objPrinter In $colInstalledPrinters
$result = DllCall("winspool.drv", "long", "DeviceCapabilitiesA", "str", $objPrinter.Name, "str", $objPrinter.PortName, "int", $DC_PAPERS, "str", Chr(0), "long", 0)
$s_struct = ""
_DebugSetup ($s_struct)
$s_struct=_StringRepeat("0", $result[0]*64)
;$s_struct = StringTrimRight($s_struct, 1)
$struct = DllStructCreate($s_struct)
$result2 = DllCall("winspool.drv", "long", "DeviceCapabilitiesA", "str", $objPrinter.Name, "str", $objPrinter.PortName, "int", $DC_PAPERNAMES, "ptr", DllStructGetPtr($struct), "long", 0)
_DebugOut ( $objPrinter.Name)
For $i = 0 To $result[0]-1
_DebugOut (DllStructGetData($struct, $i))
Next
$struct = 0
Next

Answer 1

Check this out: http://msdn.microsoft.com/en-us/library/aa394363(v=vs.85).aspx
Example that uses just WMI:
#include <Array.au3>
$objWMIService = ObjGet("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2")
$colInstalledPrinters = $objWMIService.ExecQuery ("Select * from Win32_Printer",Default,48)
For $objPrinter In $colInstalledPrinters
$arr = $objPrinter.PrinterPaperNames
_ArrayDisplay($arr, $objPrinter.Name)
Next
Or try this which prints the actual paper names (run in SciTE so you can see the output from ConsoleWrite):
Const $DC_PAPERS = 2
Const $DC_PAPERSIZE = 3
Const $DC_PAPERNAMES = 16
$objWMIService = ObjGet("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2")
$colInstalledPrinters = $objWMIService.ExecQuery ("Select Name, PortName from Win32_Printer")
For $objPrinter In $colInstalledPrinters
$result = DllCall("winspool.drv", "long", "DeviceCapabilitiesA", "str", $objPrinter.Name, "str", $objPrinter.PortName, "int", $DC_PAPERS, "str", Chr(0), "long", 0)
$s_struct = ""
$s_struct2 = ""
For $i = 1 To $result[0]
$s_struct = $s_struct & "char[64];"
Next
For $i = 1 To $result[0]
$s_struct2 &= "long x;long y;"
Next
$s_struct = StringTrimRight($s_struct, 1)
$s_struct2 = StringTrimRight($s_struct2, 1)
$j = 1
$struct = DllStructCreate($s_struct)
$pointStruct = DllStructCreate($s_struct2)
$result2 = DllCall("winspool.drv", "long", "DeviceCapabilitiesA", "str", $objPrinter.Name, "str", $objPrinter.PortName, "int", $DC_PAPERNAMES, "ptr", DllStructGetPtr($struct), "long", 0)
$result3 = DllCall("winspool.drv", "long", "DeviceCapabilitiesA", "str", $objPrinter.Name, "str", $objPrinter.PortName, "int", $DC_PAPERSIZE, "ptr", DllStructGetPtr($pointStruct), "long", 0)
ConsoleWrite($objPrinter.Name & " on Port: " & $objPrinter.PortName & #CRLF)
For $i = 1 To $result[0]
ConsoleWrite(DllStructGetData($struct, $i) & " (" & DllStructGetData($pointStruct, $j) & "mm x " & DllStructGetData($pointStruct, $j + 1) & "mm)" & #CRLF)
$j += 2
Next
$struct = 0
$pointStruct = 0
Next