Example of using signals and slots with derived classes. Sample made for Cinder. Simply create an empty Cinder application called "Signals" using TinderBox, then replace the contents of ```SignalsApp.cpp``` with this code.

SignalsApp.cpp

#define _SCL_SECURE_NO_WARNINGS

#include "cinder/app/AppNative.h"
#include "cinder/gl/gl.h"

using namespace ci;
using namespace ci::app;
using namespace std;

//--------------------------
// Button base class
//--------------------------
class Button
{
public:
	Button() : mRect( Rectf(0, 0, 300, 100) ), mIsPressed(false) {}
	Button( const Rectf& rect ) : mRect(rect), mIsPressed(false) {}
	virtual ~Button() {}

	virtual void draw();

	virtual void mouseDown( MouseEvent event );
	virtual void mouseUp( MouseEvent event );
public:
	ci::signals::signal<void( Button& )> sClicked;
private:
	bool	mIsPressed;
	Rectf	mRect;
};

void Button::draw()
{
	gl::color( mIsPressed ? Color(1, 0, 0) : Color(0, 1, 0) );
	gl::drawSolidRect( mRect );
}

void Button::mouseDown( MouseEvent event )
{
	mIsPressed = mRect.contains(event.getPos());
}

void Button::mouseUp( MouseEvent event )
{
	if (mIsPressed && mRect.contains(event.getPos()))
		sClicked(*this);

	mIsPressed = false;
}

//--------------------------
// LoginButton derived class
//--------------------------
class LoginButton : public Button
{
public:
	LoginButton() : Button( Rectf(0, 150, 300, 250) ) {}
	LoginButton( const Rectf& rect ) : Button(rect) {}
	~LoginButton() {}
};

//--------------------------
// Application class
//--------------------------
class SignalsApp : public AppNative {
public:
	void setup();
	void draw();

	void mouseDown( MouseEvent event );	
	void mouseUp( MouseEvent event );

	void onButtonClicked( Button& button );
private:
	Button			mButton;
	LoginButton		mLoginButton;
};

void SignalsApp::setup()
{
	mButton.sClicked.connect( std::bind( &SignalsApp::onButtonClicked, this, std::_1 ) );
	mLoginButton.sClicked.connect( std::bind( &SignalsApp::onButtonClicked, this, std::_1 ) );
}

void SignalsApp::draw()
{
	gl::clear(); 

	mButton.draw();
	mLoginButton.draw();
}

void SignalsApp::mouseDown( MouseEvent event )
{
	mButton.mouseDown( event );
	mLoginButton.mouseDown( event );
}

void SignalsApp::mouseUp( MouseEvent event )
{
	mButton.mouseUp( event );
	mLoginButton.mouseUp( event );
}

void SignalsApp::onButtonClicked( Button& button )
{
	try {
		LoginButton& btn = dynamic_cast<LoginButton&>( button );
		console() << "LoginButton clicked" << std::endl;
	}
	catch( ... /*const std::bad_cast &e*/ ) {
		// it didn't work, so it's not a LoginButton
		console() << "Button clicked" << std::endl;
	}
}

CINDER_APP_NATIVE( SignalsApp, RendererGl )