Код
procedure TForm1.Button3Click(Sender: TObject);
begin
if clipping then
begin
button3.Caption:='On';
clipping:=False;
exit;
end
else
begin
button3.Caption:='Off';
clipping:=true;
while clipping do
begin
out32(888,255);
sleep(100);
application.ProcessMessages;
out32(888,0);
end;
end;
end;