TProgressBar cíclico nativo (marquee) (añadida solución 3)

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Posteo el resultado completo

Código Delphi [-]
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ComCtrls, XPMan;

type
  TForm1 = class(TForm)
    ProgressBar1: TProgressBar;
    Button1: TButton;
    Button2: TButton;
    XPManifest1: TXPManifest;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

const
  PBS_MARQUEE = $08;
  PBS_SETMARQUEE = (WM_USER + 10);

procedure TForm1.Button1Click(Sender: TObject);
begin
SendMessage(ProgressBar1.Handle, PBS_SETMARQUEE, 1, 200);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
SendMessage(ProgressBar1.Handle, PBS_SETMARQUEE, 0, 200);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  SetWindowLong(ProgressBar1.Handle, GWL_STYLE, GetWindowLong(ProgressBar1.Handle, GWL_STYLE) or PBS_MARQUEE);
  // sin parpadeos
  ProgressBar1.DoubleBuffered:=True;

end;