TPen = class(TGraphicsObject)
  private
    FMode: TPenMode;
    procedure GetData(var PenData: TPenData);
    procedure SetData(const PenData: TPenData);
  protected
    function GetColor: TColor;
    procedure SetColor(Value: TColor);
    function GetHandle: HPen;
    procedure SetHandle(Value: HPen);
    procedure SetMode(Value: TPenMode);
    function GetStyle: TPenStyle;
    procedure SetStyle(Value: TPenStyle);
    function GetWidth: Integer;
    procedure SetWidth(Value: Integer);
  public
    constructor Create;
    destructor Destroy; override;
    procedure Assign(Source: TPersistent); override;
    property Handle: HPen read GetHandle write SetHandle;
  published
    property Color: TColor read GetColor write SetColor default clBlack;
    property Mode: TPenMode read FMode write SetMode default pmCopy;
    property Style: TPenStyle read GetStyle write SetStyle default psSolid;
    property Width: Integer read GetWidth write SetWidth default 1;
  end;

Canvas.Pen.Color := clRed;
Canvas.Pen.Style := psSolid ;  
//或：Canvas.Pen.Style := TPenStyle(0);

var
  qX, qY: Integer;
procedure TForm1.BitBtn1Click(Sender: TObject);
begin
  Timer1.Enabled:=not Timer1.Enabled;
  if Timer1.Enabled then begin
    WindowState := wsMaximized;
    Timer1.Interval := 50;
    Randomize;
  end else begin
    WindowState := wsNormal;
  end;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  qX := Random(Screen.Width - 10);
  qY := Random(Screen.Height - 10);
  Canvas.Pen.Color := Random(65535);
  case Random(5) of
    0: Canvas.Pen.Style := psSolid;
    1: Canvas.Pen.Style := psDash;
    2: Canvas.Pen.Style := psDot;
    3: Canvas.Pen.Style := psDashDot;
    4: Canvas.Pen.Style := psDashDotDot;
  end;
  Canvas.Rectangle(qX, qY, qX + Random(400), qY + Random(400));
end;

type TPenMode = (pmBlack, pmWhite, pmNop, pmNot, pmCopy, pmNotCopy, pmMergePenNot, pmMaskPenNot, pmMergeNotPen, pmMaskNotPen, pmMerge, pmNotMerge, pmMask, pmNotMask, pmXor, pmNotXor);

Canvas.Pen.Mode := pmBlack;
//或：Canvas.Pen.Mode := TPenMode(0);