void GuiExecWait(Callback cb, int execDelay_ms = 20) {
	Mutex mtx;
	mtx.Enter();
	{
		// enter new context to avoid mtx destruction before cond destruction ( due to bad compiler optimizations )
		ConditionVariable cond;
		cb << callback( &cond, &ConditionVariable::Signal );
		SetTimeCallback(execDelay_ms, cb);
		cond.Wait(mtx);
	}
}