function TMyControl.GetVisibleRect: TRect;
var
  vParent: TWinControl;
  vRect, vParentRect: TRect;
  vP:      TPoint;
begin
  assert(assigned(Parent));

  vRect := BoundsRect; // Le TControl en entier, pas juste ClientRect
  if assigned(Parent) then
  begin
    vParent := Parent;
    vP      := ControlOrigin;
    vRect.Offset(vP);

    { On scan tous les Parents }
    while assigned(vParent) and not (vRect.IsEmpty) do
    begin
      vParentRect := vParent.ClientToScreen(vParent.ClientRect);
      vRect       := vRect.Intersect(vRect, vParentRect);
      vParent     := vParent.Parent;
    end;

    if not vRect.IsEmpty then vRect.Offset(-vP.X, -vP.y);

  end;

  Result := vRect;

end;