// MyControlType must be deriveed from DockableCtrl
void AddCtrl() {
	DockableCtrl &dc = DockWindow::CreateDockable<MyControlType>("Title");
	dc.WhenState = THISBACK1(OnDockerState, &dc);
	Float(dc);
}

void OnDockerState(DockableCtrl *dc) {
	if (dc->IsHidden())
		DockWindow::Deregister(*dc);	
}