#include <CtrlLib/CtrlLib.h>
using namespace Upp;

class RestrictedTopWindow:public TopWindow{
	TopWindow* parent;
	typedef RestrictedTopWindow CLASSNAME;
public:
	RestrictedTopWindow(TopWindow* parent):parent(parent){
		SetTimeCallback(-50,THISBACK(CheckPos));
	}
	void CheckPos(){
		Rect allowed=parent->GetRect();
		Rect r=GetRect();
		if(!r.Contains(allowed)){
			SetRect(minmax(r.left,allowed.left,allowed.right-r.GetWidth()),
			        minmax(r.top,allowed.top,allowed.bottom-r.GetHeight()),
			        r.GetWidth(),r.GetHeight());
		}
	}
};

class App :public TopWindow {
	typedef App CLASSNAME;
public:
	RestrictedTopWindow rtw;
	App():rtw(this){
		Title("MainWindow");
	}
	void LeftUp(Point p,dword){
		rtw.SetRect(p.x,p.y,200,100);
		rtw.Title("Child window").Sizeable().Run();	
	}
};

GUI_APP_MAIN{
	App().Sizeable().Run();
}