unit PaintThread;

interface

uses
  Classes;

type
  TPaintThread = class( TThread )

  private
    procedure Zeichnen;
  protected
    procedure Execute; override;
  end;

implementation

uses
  SysUtils,
  Windows;

{ TPaintThread }

procedure TPaintThread.Execute;
begin

  if MainThreadID = GetCurrentThreadId
  then
    raise Exception.Create( 'Upps, ich darf nicht im MainThread-Kontext sein!' );

  inherited;
  while not Terminated do
    begin
      Synchronize( Zeichnen );
      Sleep( 1 );
    end;
end;

procedure TPaintThread.Zeichnen;
begin
  if MainThreadID <> GetCurrentThreadId
  then
    raise Exception.Create( 'Upps, ich bin nicht im MainThread-Kontext!' );

end;

end.

unit FormMain;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics,
  Controls, Forms, Dialogs,
  PaintThread;

type
  TForm1 = class( TForm )
  private
    FPaintThread : TPaintThread;
  public
    procedure AfterConstruction; override;
    procedure BeforeDestruction; override;
  end;

var
  Form1 : TForm1;

implementation

{$R *.dfm}
{ TForm1 }

procedure TForm1.AfterConstruction;
begin
  inherited;
  FPaintThread := TPaintThread.Create( False );
end;

procedure TForm1.BeforeDestruction;
begin
  inherited;
  FPaintThread.Free;
end;

end.