Chip 1997 April/Chip_1997-04_cd.bin/prezent/cb/data.z/PRINTERS.PAS

Pascal/Delphi Source File | 1997-01-16 | 24KB | 880 lines

{*******************************************************}
{                                                       }
{       Delphi Visual Component Library                 }
{                                                       }
{       Copyright (c) 1995,96 Borland International     }
{                                                       }
{*******************************************************}

unit Printers;

{$R-}

interface

uses Windows, WinSpool, SysUtils, Classes, Graphics, Forms;

type
  EPrinter = class(Exception);

  { TPrinter }

  { The printer object encapsulates the printer interface of Windows.  A print
    job is started whenever any redering is done either through a Text variable
    or the printers canvas.  This job will stay open until EndDoc is called or
    the Text variable is closed.  The title displayed in the Print Manager (and
    on network header pages) is determined by the Title property.

    EndDoc - Terminates the print job (and closes the currently open Text).
      The print job will being printing on the printer after a call to EndDoc.
    NewPage - Starts a new page and increments the PageNumber property.  The
      pen position of the Canvas is put back at (0, 0).
    Canvas - Represents the surface of the currently printing page.  Note that
      some printer do not support drawing pictures and the Draw, StretchDraw,
      and CopyRect methods might fail.
    Fonts - The list of fonts supported by the printer.  Note that TrueType
      fonts appear in this list even if the font is not supported natively on
      the printer since GDI can render them accurately for the printer.
    PageHeight - The height, in pixels, of the page.
    PageWidth - The width, in pixels, of the page.
    PageNumber - The current page number being printed.  This is incremented
      when ever the NewPage method is called.  (Note: This property can also be
      incremented when a Text variable is written, a CR is encounted on the
      last line of the page).
    PrinterIndex - Specifies which printer in the TPrinters list that is
      currently selected for printing.  Setting this property to -1 will cause
      the default printer to be selected.  If this value is changed EndDoc is
      called automatically.
    Printers - A list of the printers installed in Windows.
    Title - The title used by Windows in the Print Manager and for network
      title pages. }

  TPrinterState = (psNoHandle, psHandleIC, psHandleDC);
  TPrinterOrientation = (poPortrait, poLandscape);
  TPrinterCapability = (pcCopies, pcOrientation, pcCollation);
  TPrinterCapabilities = set of TPrinterCapability;

  TPrinter = class(TObject)
  private
    FCanvas: TCanvas;
    FFonts: TStrings;
    FPageNumber: Integer;
    FPrinters: TStrings;
    FPrinterIndex: Integer;
    FTitle: string;
    FPrinting: Boolean;
    FAborted: Boolean;
    FCapabilities: TPrinterCapabilities;
    State: TPrinterState;
    DC: HDC;
    DevMode: PDeviceMode;
    DeviceMode: THandle;
    FPrinterHandle: THandle;
    procedure SetState(Value: TPrinterState);
    function GetCanvas: TCanvas;
    function GetNumCopies: Integer;
    function GetFonts: TStrings;
    function GetHandle: HDC;
    function GetOrientation: TPrinterOrientation;
    function GetPageHeight: Integer;
    function GetPageWidth: Integer;
    function GetPrinterIndex: Integer;
    procedure SetPrinterCapabilities(Value: Integer);
    procedure SetPrinterIndex(Value: Integer);
    function GetPrinters: TStrings;
    procedure SetNumCopies(Value: Integer);
    procedure SetOrientation(Value: TPrinterOrientation);
    procedure SetToDefaultPrinter;
    procedure CheckPrinting(Value: Boolean);
    procedure FreePrinters;
    procedure FreeFonts;
  public
    constructor Create;
    destructor Destroy; override;
    procedure Abort;
    procedure BeginDoc;
    procedure EndDoc;
    procedure NewPage;
    procedure GetPrinter(ADevice, ADriver, APort: PChar; var ADeviceMode: THandle);
    procedure SetPrinter(ADevice, ADriver, APort: PChar; ADeviceMode: THandle);
    property Aborted: Boolean read FAborted;
    property Canvas: TCanvas read GetCanvas;
    property Capabilities: TPrinterCapabilities read FCapabilities;
    property Copies: Integer read GetNumCopies write SetNumCopies;
    property Fonts: TStrings read GetFonts;
    property Handle: HDC read GetHandle;
    property Orientation: TPrinterOrientation read GetOrientation write SetOrientation;
    property PageHeight: Integer read GetPageHeight;
    property PageWidth: Integer read GetPageWidth;
    property PageNumber: Integer read FPageNumber;
    property PrinterIndex: Integer read GetPrinterIndex write SetPrinterIndex;
    property Printing: Boolean read FPrinting;
    property Printers: TStrings read GetPrinters;
    property Title: string read FTitle write FTitle;
  end;

{ Printer function - Replaces the Printer global variable of previous versions,
  to improve smart linking (reduce exe size by 2.5k in projects that don't use
  the printer).  Code which assigned to the Printer global variable
  must call SetPrinter instead.  SetPrinter returns current printer object
  and makes the new printer object the current printer.  It is the caller's
  responsibility to free the old printer, if appropriate.  (This allows
  toggling between different printer objects without destroying configuration
  settings.) }

function Printer: TPrinter;
function SetPrinter(NewPrinter: TPrinter): TPrinter;

{ AssignPrn - Assigns a Text variable to the currently selected printer.  Any
  Write or Writeln's going to that file variable will be written on the
  printer using the Canvas property's font.  A new page is automatically
  started if a CR is encountered on (or a Writeln is written to) the last
  line on the page.  Closing the text file will imply a call to the
  Printer.EndDoc method. Note: only one Text variable can be open on the
  printer at a time.  Opening a second will cause an exception.}

procedure AssignPrn(var F: Text);

implementation

uses Consts;

var
  FPrinter: TPrinter;

function FetchStr(var Str: PChar): PChar;
var
  P: PChar;
begin
  Result := Str;
  if Str = nil then Exit;
  P := Str;
  while P^ = ' ' do Inc(P);
  Result := P;
  while (P^ <> #0) and (P^ <> ',') do Inc(P);
  if P^ = ',' then
  begin
    P^ := #0;
    Inc(P);
  end;
  Str := P;
end;

procedure RaiseError(MsgID: Integer);
begin
  raise EPrinter.CreateRes(MsgID);
end;

function AbortProc(Prn: HDC; Error: Integer): Bool; stdcall;
begin
  Application.ProcessMessages;
  Result := not FPrinter.Aborted;
end;

type
  PrnRec = record
    case Integer of
      1: (
        Cur: TPoint;
        Finish: TPoint;         { End of the printable area }
        Height: Integer);       { Height of the current line }
      2: (
        Tmp: array[1..32] of Char);
  end;

procedure NewPage(var Prn: PrnRec);
begin
  with Prn do
  begin
    Cur.X := 0;
    Cur.Y := 0;
    FPrinter.NewPage;
  end;
end;

{ Start a new line on the current page, if no more lines left start a new
  page. }
procedure NewLine(var Prn: PrnRec);

  function CharHeight: Word;
  var
    Metrics: TTextMetric;
  begin
    GetTextMetrics(FPrinter.Canvas.Handle, Metrics);
    Result := Metrics.tmHeight;
  end;

begin
  with Prn do
  begin
    Cur.X := 0;
    if Height = 0 then
      Inc(Cur.Y, CharHeight) else
      Inc(Cur.Y, Height);
    if Cur.Y > (Finish.Y - (Height * 2)) then NewPage(Prn);
    Height := 0;
  end;
end;

{ Print a string to the printer without regard to special characters.  These
  should handled by the caller. }
procedure PrnOutStr(var Prn: PrnRec; Text: PChar; Len: Integer);
var
  Extent: TSize;
  L: Integer;
begin
  with Prn, FPrinter.Canvas do
  begin
    while Len > 0 do
    begin
      L := Len;
      GetTextExtentPoint(Handle, Text, L, Extent);

      while (L > 0) and (Extent.cX + Cur.X > Finish.X) do
      begin
        L := CharPrev(Text, Text+L) - Text;
        GetTextExtentPoint(Handle, Text, L, Extent);
      end;

      if Extent.cY > Height then Height := Extent.cY + 2;
      Windows.TextOut(Handle, Cur.X, Cur.Y, Text, L);
      Dec(Len, L);
      Inc(Text, L);
      if Len > 0 then NewLine(Prn)
      else Inc(Cur.X, Extent.cX);
    end;
  end;
end;

{ Print a string to the printer handling special characters. }
procedure PrnString(var Prn: PrnRec; Text: PChar; Len: Integer);
var
  L: Integer;
  TabWidth: Word;

  procedure Flush;
  begin
    if L <> 0 then PrnOutStr(Prn, Text, L);
    Inc(Text, L + 1);
    Dec(Len, L + 1);
    L := 0;
  end;

  function AvgCharWidth: Word;
  var
    Metrics: TTextMetric;
  begin
    GetTextMetrics(FPrinter.Canvas.Handle, Metrics);
    Result := Metrics.tmAveCharWidth;
  end;

begin
  L := 0;
  with Prn do
  begin
    while L < Len do
    begin
      case Text[L] of
        #9:
          begin
            Flush;
            TabWidth := AvgCharWidth * 8;
            Inc(Cur.X, TabWidth - ((Cur.X + TabWidth + 1)
              mod TabWidth) + 1);
            if Cur.X > Finish.X then NewLine(Prn);
          end;
        #13: Flush;
        #10:
          begin
            Flush;
            NewLine(Prn);
          end;
        ^L:
          begin
            Flush;
            NewPage(Prn);
          end;
      else
        Inc(L);
      end;
    end;
  end;
  Flush;
end;

{ Called when a Read or Readln is applied to a printer file. Since reading is
  illegal this routine tells the I/O system that no characters where read, which
  generates a runtime error. }
function PrnInput(var F: TTextRec): Integer;
begin
  with F do
  begin
    BufPos := 0;
    BufEnd := 0;
  end;
  Result := 0;
end;

{ Called when a Write or Writeln is applied to a printer file. The calls
  PrnString to write the text in the buffer to the printer. }
function PrnOutput(var F: TTextRec): Integer;
begin
  with F do
  begin
    PrnString(PrnRec(UserData), PChar(BufPtr), BufPos);
    BufPos := 0;
    Result := 0;
  end;
end;

{ Will ignore certain requests by the I/O system such as flush while doing an
  input. }
function PrnIgnore(var F: TTextRec): Integer;
begin
  Result := 0;
end;

{ Deallocates the resources allocated to the printer file. }
function PrnClose(var F: TTextRec): Integer;
begin
  with PrnRec(F.UserData) do
  begin
    FPrinter.EndDoc;
    Result := 0;
  end;
end;

{ Called to open I/O on a printer file.  Sets up the TTextFile to point to
  printer I/O functions. }
function PrnOpen(var F: TTextRec): Integer;
const
  Blank: array[0..0] of Char = '';
begin
  with F, PrnRec(UserData) do
  begin
    if Mode = fmInput then
    begin
      InOutFunc := @PrnInput;
      FlushFunc := @PrnIgnore;
      CloseFunc := @PrnIgnore;
    end else
    begin
      Mode := fmOutput;
      InOutFunc := @PrnOutput;
      FlushFunc := @PrnOutput;
      CloseFunc := @PrnClose;
      FPrinter.BeginDoc;

      Cur.X := 0;
      Cur.Y := 0;
      Finish.X := FPrinter.PageWidth;
      Finish.Y := FPrinter.PageHeight;
      Height := 0;
    end;
    Result := 0;
  end;
end;

procedure AssignPrn(var F: Text);
begin
  with TTextRec(F), PrnRec(UserData) do
  begin
    Printer;
    FillChar(F, SizeOf(F), 0);
    Mode := fmClosed;
    BufSize := SizeOf(Buffer);
    BufPtr := @Buffer;
    OpenFunc := @PrnOpen;
  end;
end;

{ TPrinterDevice }

type
  TPrinterDevice = class
    Driver, Device, Port: String;
    constructor Create(ADriver, ADevice, APort: PChar);
    function IsEqual(ADriver, ADevice, APort: PChar): Boolean;
  end;

constructor TPrinterDevice.Create(ADriver, ADevice, APort: PChar);
begin
  inherited Create;
  Driver := ADriver;
  Device := ADevice;
  Port := APort;
end;

function TPrinterDevice.IsEqual(ADriver, ADevice, APort: PChar): Boolean;
begin
  Result := (Device = ADevice) and (Port = APort);
end;

{ TPrinterCanvas }

type
  TPrinterCanvas = class(TCanvas)
    Printer: TPrinter;
    constructor Create(APrinter: TPrinter);
    procedure CreateHandle; override;
    procedure Changing; override;
    procedure UpdateFont;
  end;

constructor TPrinterCanvas.Create(APrinter: TPrinter);
begin
  inherited Create;
  Printer := APrinter;
end;

procedure TPrinterCanvas.CreateHandle;
begin
  Printer.SetState(psHandleIC);
  UpdateFont;
  Handle:= Printer.DC;
end;

procedure TPrinterCanvas.Changing;
begin
  Printer.CheckPrinting(True);
  inherited Changing;
  UpdateFont;
end;

procedure TPrinterCanvas.UpdateFont;
var
  FontSize: Integer;
begin
  if GetDeviceCaps(Printer.DC, LOGPIXELSY) <> Font.PixelsPerInch then
  begin
    FontSize := Font.Size;
    Font.PixelsPerInch := GetDeviceCaps(Printer.DC, LOGPIXELSY);
    Font.Size := FontSize;
  end;
end;

{ TPrinter }

constructor TPrinter.Create;
begin
  inherited Create;
  FPrinterIndex := -1;
end;

destructor TPrinter.Destroy;
begin
  if Printing then EndDoc;
  SetState(psNoHandle);
  FreePrinters;
  FreeFonts;
  FCanvas.Free;
  if FPrinterHandle <> 0 then ClosePrinter(FPrinterHandle);
  inherited Destroy;
end;

procedure TPrinter.SetState(Value: TPrinterState);
type
  TCreateHandleFunc = function (DriverName, DeviceName, Output: PChar;
    InitData: PDeviceMode): HDC stdcall;
var
  CreateHandleFunc: TCreateHandleFunc;
begin
  if Value <> State then
  begin
    CreateHandleFunc := nil;
    case Value of
      psNoHandle:
        begin
          CheckPrinting(False);
          if Assigned(FCanvas) then FCanvas.Handle := 0;
          DeleteDC(DC);
          DC := 0;
        end;
      psHandleIC:
        if State <> psHandleDC then CreateHandleFunc := CreateIC
        else Exit;
      psHandleDC:
        begin
          if FCanvas <> nil then FCanvas.Handle := 0;
          if DC <> 0 then DeleteDC(DC);
          CreateHandleFunc := CreateDC;
        end;
    end;
    if Assigned(CreateHandleFunc) then
      with TPrinterDevice(Printers.Objects[PrinterIndex]) do
      begin
        DC := CreateHandleFunc(PChar(Driver), PChar(Device), PChar(Port), DevMode);
        if DC = 0 then RaiseError(SInvalidPrinter);
        if FCanvas <> nil then FCanvas.Handle := DC;
      end;
    State := Value;
  end;
end;

procedure TPrinter.CheckPrinting(Value: Boolean);
begin
  if Printing <> Value then
    if Value then RaiseError(SNotPrinting)
    else RaiseError(SPrinting);
end;

procedure TPrinter.Abort;
begin
  CheckPrinting(True);
  AbortDoc(Canvas.Handle);
  FAborted := True;
  EndDoc;
end;

procedure TPrinter.BeginDoc;
var
  CTitle: array[0..31] of Char;
  DocInfo: TDocInfo;
begin
  CheckPrinting(False);
  SetState(psHandleDC);
  Canvas.Refresh;
  TPrinterCanvas(Canvas).UpdateFont;
  FPrinting := True;
  FAborted := False;
  FPageNumber := 1;
  StrPLCopy(CTitle, Title, SizeOf(CTitle) - 1);
  FillChar(DocInfo, SizeOf(DocInfo), 0);
  with DocInfo do
  begin
    cbSize := SizeOf(DocInfo);
    lpszDocName := CTitle;
    lpszOutput := nil;
  end;
  SetAbortProc(DC, AbortProc);
  StartDoc(DC, DocInfo);
  StartPage(DC);
end;

procedure TPrinter.EndDoc;
begin
  CheckPrinting(True);
  EndPage(DC);
  if not Aborted then Windows.EndDoc(DC);
  FPrinting := False;
  FAborted := False;
  FPageNumber := 0;
end;

procedure TPrinter.NewPage;
begin
  CheckPrinting(True);
  EndPage(DC);
  StartPage(DC);
  Inc(FPageNumber);
  Canvas.Refresh;
end;

procedure TPrinter.GetPrinter(ADevice, ADriver, APort: PChar; var ADeviceMode: THandle);
begin
  ADeviceMode := DeviceMode;
  with TPrinterDevice(Printers.Objects[PrinterIndex]) do
  begin
    StrCopy(ADevice, PChar(Device));
    StrCopy(ADriver, PChar(Driver));
    StrCopy(APort, PChar(Port));
  end;
end;

procedure TPrinter.SetPrinterCapabilities(Value: Integer);
begin
  FCapabilities := [];
  if (Value and DM_ORIENTATION) <> 0 then
    Include(FCapabilities, pcOrientation);
  if (Value and DM_COPIES) <> 0 then
    Include(FCapabilities, pcCopies);
  if (Value and DM_COLLATE) <> 0 then
    Include(FCapabilities, pcCollation);
end;

procedure TPrinter.SetPrinter(ADevice, ADriver, APort: PChar; ADeviceMode: THandle);
var
  I, J: Integer;
  StubDevMode: TDeviceMode;
begin
  CheckPrinting(False);
  if ADeviceMode <> DeviceMode then
  begin
    if DeviceMode <> 0 then
    begin
      GlobalUnlock(DeviceMode);
      GlobalFree(DeviceMode);
    end;
    DeviceMode := ADeviceMode;
    if DeviceMode <> 0 then
    begin
      DevMode := GlobalLock(DeviceMode);
      SetPrinterCapabilities(DevMode.dmFields);
    end;
  end;
  FreeFonts;
  if FPrinterHandle <> 0 then
  begin
    ClosePrinter(FPrinterHandle);
    FPrinterHandle := 0;
  end;
  SetState(psNoHandle);
  J := -1;
  for I := 0 to Printers.Count - 1 do
  begin
    if TPrinterDevice(Printers.Objects[I]).IsEqual(ADriver, ADevice, APort) then
    begin
      J := I;
      Break;
    end;
  end;
  if J = -1 then
  begin
    J := FPrinters.Count;
    FPrinters.AddObject(FmtLoadStr(SDeviceOnPort, [ADevice, APort]),
      TPrinterDevice.Create(ADriver, ADevice, APort));
  end;
  FPrinterIndex := J;
  if OpenPrinter(ADevice, FPrinterHandle, nil) and (DeviceMode = 0) then
  begin
    DeviceMode := GlobalAlloc(GHND,
      DocumentProperties(0, FPrinterHandle, ADevice, StubDevMode,
      StubDevMode, 0));
    if DeviceMode <> 0 then
    begin
      DevMode := GlobalLock(DeviceMode);
      if DocumentProperties(0, FPrinterHandle, ADevice, DevMode^,
        DevMode^, DM_OUT_BUFFER) < 0 then
      begin
        GlobalUnlock(DeviceMode);
        GlobalFree(DeviceMode);
        DeviceMode := 0;
      end
      else SetPrinterCapabilities(DevMode^.dmFields);
    end;
  end;
end;

function TPrinter.GetCanvas: TCanvas;
begin
  if FCanvas = nil then FCanvas := TPrinterCanvas.Create(Self);
  Result := FCanvas;
end;

function EnumFontsProc(var LogFont: TLogFont; var TextMetric: TTextMetric;
  FontType: Integer; Data: Pointer): Integer; stdcall;
begin
  TStrings(Data).Add(LogFont.lfFaceName);
  Result := 1;
end;

function TPrinter.GetFonts: TStrings;
begin
  if FFonts = nil then
  try
    SetState(psHandleIC);
    FFonts := TStringList.Create;
    EnumFonts(DC, nil, @EnumFontsProc, Pointer(FFonts));
  except
    FFonts.Free;
    FFonts := nil;
    raise;
  end;
  Result := FFonts;
end;

function TPrinter.GetHandle: HDC;
begin
  SetState(psHandleIC);
  Result := DC;
end;

function TPrinter.GetNumCopies: Integer;
begin
  GetPrinterIndex;
  if DeviceMode = 0 then RaiseError(SInvalidPrinterOp);
  Result := DevMode^.dmCopies;
end;

procedure TPrinter.SetNumCopies(Value: Integer);
begin
  CheckPrinting(False);
  GetPrinterIndex;
  if DeviceMode = 0 then RaiseError(SInvalidPrinterOp);
  SetState(psNoHandle);
  DevMode^.dmCopies := Value;
end;

function TPrinter.GetOrientation: TPrinterOrientation;
begin
  GetPrinterIndex;
  if DeviceMode = 0 then RaiseError(SInvalidPrinterOp);
  if DevMode^.dmOrientation = DMORIENT_PORTRAIT then Result := poPortrait
  else Result := poLandscape;
end;

procedure TPrinter.SetOrientation(Value: TPrinterOrientation);
const
  Orientations: array [TPrinterOrientation] of Integer = (
    DMORIENT_PORTRAIT, DMORIENT_LANDSCAPE);
begin
  CheckPrinting(False);
  GetPrinterIndex;
  if DeviceMode = 0 then RaiseError(SInvalidPrinterOp);
  SetState(psNoHandle);
  DevMode^.dmOrientation := Orientations[Value];
end;

function TPrinter.GetPageHeight: Integer;
begin
  SetState(psHandleIC);
  Result := GetDeviceCaps(DC, VertRes);
end;

function TPrinter.GetPageWidth: Integer;
begin
  SetState(psHandleIC);
  Result := GetDeviceCaps(DC, HorzRes);
end;

function TPrinter.GetPrinterIndex: Integer;
begin
  if FPrinterIndex = -1 then SetToDefaultPrinter;
  Result := FPrinterIndex;
end;

procedure TPrinter.SetPrinterIndex(Value: Integer);
begin
  CheckPrinting(False);
  if (Value = -1) or (PrinterIndex = -1) then SetToDefaultPrinter
  else if (Value < 0) or (Value >= Printers.Count) then RaiseError(SPrinterIndexError);
  FPrinterIndex := Value;
  FreeFonts;
  SetState(psNoHandle);
end;

function TPrinter.GetPrinters: TStrings;
var
  LineCur, Port: PChar;
  Buffer, PrinterInfo: PChar;
  I, Count, NumInfo: Integer;
  Flags: Integer;
  Level: Byte;
begin
  if FPrinters = nil then
  begin
    FPrinters := TStringList.Create;
    Result := FPrinters;
    try
      if Win32Platform = VER_PLATFORM_WIN32_NT then
      begin
        Flags := PRINTER_ENUM_CONNECTIONS or PRINTER_ENUM_LOCAL;
        Level := 4;
      end
      else
      begin
        Flags := PRINTER_ENUM_LOCAL;
        Level := 5;
      end;
      EnumPrinters(Flags, nil, Level, nil, 0, Count, NumInfo);
      GetMem(Buffer, Count);
      try
        if not EnumPrinters(Flags, nil, Level, PByte(Buffer), Count, Count, NumInfo) then
          Exit;
        PrinterInfo := Buffer;
        for I := 0 to NumInfo - 1 do
        begin
          if Level = 4 then
            with PPrinterInfo4(PrinterInfo)^ do
            begin
              FPrinters.AddObject(pPrinterName,
                TPrinterDevice.Create(nil, pPrinterName, nil));
              Inc(PrinterInfo, sizeof(TPrinterInfo4));
            end
          else
            with PPrinterInfo5(PrinterInfo)^ do
            begin
              LineCur := pPortName;
              Port := FetchStr(LineCur);
              while Port^ <> #0 do
              begin
                FPrinters.AddObject(FmtLoadStr(SDeviceOnPort, [pPrinterName, Port]),
                  TPrinterDevice.Create(nil, pPrinterName, Port));
                Port := FetchStr(LineCur);
              end;
              Inc(PrinterInfo, sizeof(TPrinterInfo5));
            end;
        end;
      finally
        FreeMem(Buffer, Count);
      end;
    except
      FPrinters.Free;
      FPrinters := nil;
      raise;
    end;
  end;
  Result := FPrinters;
end;

procedure TPrinter.SetToDefaultPrinter;
var
  I: Integer;
  DefaultPrinter: array[0..79] of Char;
  Cur, Device: PChar;
begin
  GetProfileString('windows', 'device', '', DefaultPrinter,
    SizeOf(DefaultPrinter) - 1);
  Cur := DefaultPrinter;
  Device := FetchStr(Cur);
  with Printers do
    for I := 0 to Count-1 do
    begin
      if TPrinterDevice(Objects[I]).Device = Device then
      begin
        with TPrinterDevice(Objects[I]) do
          SetPrinter(PChar(Device), PChar(Driver), PChar(Port), 0);
        Exit;
      end;
    end;
  RaiseError(SNoDefaultPrinter);
end;

procedure TPrinter.FreePrinters;
var
  I: Integer;
begin
  if FPrinters <> nil then
  begin
    for I := 0 to FPrinters.Count - 1 do
      FPrinters.Objects[I].Free;
    FPrinters.Free;
    FPrinters := nil;
  end;
end;

procedure TPrinter.FreeFonts;
begin
  FFonts.Free;
  FFonts := nil;
end;

function Printer: TPrinter;
begin
  if FPrinter = nil then FPrinter := TPrinter.Create;
  Result := FPrinter;
end;

function SetPrinter(NewPrinter: TPrinter): TPrinter;
begin
  Result := FPrinter;
  FPrinter := NewPrinter;
end;

initialization
  FPrinter := nil;
finalization
  FPrinter.Free;
end.