EnumPrinters schlägt fehl

[Luckie]

Ich versuche so alle lokalen Drucker zu bekommen:

Delphi-Quellcode:

procedure GetPrinters;
var
  dwNeeded          : DWORD;
  dwReturn          : DWORD;
  pinfo4            : PPrinterInfo4;
  pWork             : PPrinterInfo4;
  i                 : Integer;
  s                 : string;
begin
  dwNeeded := 0;
  dwReturn := 0;
  EnumPrinters(PRINTER_ENUM_LOCAL, nil, 4, nil, 0, dwNeeded, dwReturn);
  GetMem(pinfo4, dwNeeded);
  try
    if EnumPrinters(PRINTER_ENUM_LOCAL, nil, 4, PByte(pinfo4), sizeof(pinfo4), dwNeeded, dwReturn) then
    begin
      pWork := pinfo4;
      for i := 0 to dwReturn - 1 do
      begin
        s := string(pWork.pPrinterName);
        MessageBox(hApp, PChar(s), '', 0);
        Inc(pWork, sizeof(pWork));
      end;
    end
    else
      MessageBox(hApp, PChar(SysErrorMessage(GetLastError)), '', 0);
  finally
    FreeMem(pinfo4);
  end;
end;

Aber leider schlägt EnumPrinters mit der Fehlermeldung:

Zitat:

Der an einen Systemaufruf übergebene Datenbereich ist zu klein

fehl. Was ich irgendwie nicht so ganz verstehe.

Anstatt sizeof(pinfo4) muss es natürlich dwNeeded heißen:

Delphi-Quellcode:

procedure GetPrinters;
var
  dwNeeded          : DWORD;
  dwReturn          : DWORD;
  pinfo4            : PPrinterInfo4;
  pWork             : PPrinterInfo4;
  i                 : Integer;
  s                 : string;
begin
  dwNeeded := 0;
  dwReturn := 0;
  EnumPrinters(PRINTER_ENUM_LOCAL, nil, 4, nil, 0, dwNeeded, dwReturn);
  GetMem(pinfo4, dwNeeded);
  try
    if EnumPrinters(PRINTER_ENUM_LOCAL, nil, 4, pinfo4, dwNeeded, dwNeeded, dwReturn) then
    begin
      pWork := pinfo4;
      for i := 0 to dwReturn - 1 do
      begin
        s := string(pWork.pPrinterName);
        MessageBox(hApp, PChar(s), '', 0);
        Inc(pWork);
      end;
    end
    else
      MessageBox(hApp, PChar(SysErrorMessage(GetLastError)), '', 0);
  finally
    FreeMem(pinfo4);
  end;
end;