RE: Adding a printer port - at my wits end

[Darren McBride]

Folks,

I've done it. I've done it. I can't believe it. Persistence is definitely
the key.

And the answer was add 'stdcall' to the end of my function pointer
declaration:

  fn: function(pName: PChar; pLevel: Integer; lpBuffer: Pointer;
pMonitorName: PChar): Integer; stdcall;

I can't believe it. Programming is definitely a sequence of high's and
low's.

Thanks again to Steve for his help.

Kind regards,
Darren

-----Original Message-----
From: Darren McBride [mailto:[EMAIL PROTECTED] 
Sent: 25 May 2005 02:42
To: 'Borland's Delphi Discussion List'
Subject: Adding a printer port - at my wits end

Folks,

I have tried everything, and searched everywhere. I cannot find a definitive
answer to how to add a printer port to XP and W2K. I have seen some posts on
the web say to use AddPortEx and others to use XcvData. Neither are defined
in Delphi, so both must be used via the LoadLibrary method to ensure they
exist before calling.

My problem is, firstly which to use. I have a sample program written using
AddPortEx, but it is not working (fails on the line that adds the port).
This is my code thus far:

unit UPorts;

interface

uses
  SysUtils, Dialogs, Types, Windows, Classes, WinSpool;

  procedure AddPrinterPort(Handle: HWnd; Instance: HInst; CommandLine:
PChar; ShowWindow: Integer); stdcall; export;

implementation

{$WARN SYMBOL_PLATFORM OFF}

procedure ListPorts(var PortList: TStringList); var
  i, bn, r: DWORD;
  pi, ps: PPortInfo1;
begin
  { check list object }
  if not Assigned(PortList) then
    Exit;

  { get count of ports }
  EnumPorts(nil, 1, nil, 0, bn, r);

  { reserve memory for port list }
  GetMem(pi, bn);
  try
    { process port list }
    Win32Check(EnumPorts(nil, 1, pi, bn, bn, r));
    ps := pi;
    for i := 0 to (r - 1) do
    begin
      PortList.Add(ps^.pName);
      Inc(ps);
    end;

  { free reserved memory }
  finally
    FreeMem(pi);
  end;
end;

procedure AddPrinterPort(Handle: HWnd; Instance: HInst; CommandLine: PChar;
ShowWindow: Integer); var
  pl: TStringList;
  fn: function(pName: PChar; pLevel: Integer; lpBuffer: Pointer;
pMonitorName: PChar): Integer;
  i: Integer;
  lh: THandle;
  pi: PPortInfo1;
  pn: String;
begin
  try
    { check for valid port name }
    if (Trim(CommandLine) = '') then
      Exit;

    { check for existing port name }
    pl := TStringList.Create;
    try
      ListPorts(pl);
      if (pl.IndexOf(CommandLine) >= 0) then
        Exit;
    finally
      pl.Free;
    end;

    { add new port }
    lh := LoadLibrary('winspool.drv');
    if (lh >= 32) then
    begin
      @fn := GetProcAddress(lh, 'AddPortExA');
      if (@fn <> nil) then
      begin
        GetMem(pi, SizeOf(pi));
        try
          ZeroMemory(pi, SizeOf(pi));
          pn := String(CommandLine);
          pi^.pName := PChar(pn + #0);
          i := fn(nil, 1, @pi, 'Local Port');
          if (i = 0) then
            SysErrorMessage(GetLastError);
        finally
          FreeMem(pi);
        end;
      end;
      FreeLibrary(lh);
    end;

  { handle all errors }
  except
    on e: Exception do
      ShowMessage(e.Message);
  end;
end;

end.

In the line 'i := fn(nil, 1, @pi, 'Local Port');' I have tried @pi and pi,
as I don't fully understand pointers. 

Any assistance gratefully accepted, or if you know of someone that might be
able to help. I am really desperate at this stage and I have a client
waiting on the answer.

Thanks,
Darren



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