unit main;

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

type
 TForm1 = class(TForm)
   Label1: TLabel;
   Label2: TLabel;
   ListBox1: TListBox;
   procedure WMPaint (var Message: TWMPaint); message WM_PAINT;
 protected
   procedure CreateParams (var Params: TCreateparams); override;
 end;

var
 Form1: TForm1;

implementation

{$R *.dfm}

{ TForm1 }

procedure TForm1.CreateParams(var Params: TCreateparams);
begin
 inherited;
 Params.WindowClass.style := Params.WindowClass.style or CS_OWNDC;
end;

procedure TForm1.WMPaint(var Message: TWMPaint);
begin
 ListBox1.Items.Add('WM_PAINT');
 inherited;
end;

end.