eventpp provides tools that allow your application components to communicate with each other by dispatching events and listening to them. With eventpp you can implement signal/slot mechanism, or observer pattern, very easily.

• Template based, less runtime overhead, unlimited possibilities. The event and callback can be almost any C++ types meeting minimum requirements.
• Supports nested event. A listener can dispatch event, append/prepend/insert/remove other listeners during capturing an event safely.
• Support event filter.
• Thread safe.
• Requires C++ 11 (tested with MSVC 2017, MSVC 2015, MinGW (Msys) gcc 7.2, and Ubuntu gcc 5.4).
• Backed by unit tests.
• Written in portable and standard C++. (I'm not a C++ standard expert so if you find any non-standard code or undefined behavior please let me know.)
• Doesn't depend on any other libraries.
• Header only, no source file, no need to build.

Apache License, Version 2.0
If you have trouble with the license, contact me.

https://github.com/wqking/eventpp

eventpp

// Add the folder *include* to include path.
#include "eventpp/eventdispatcher.h"

// The namespace is eventpp
// The first template parameter int is the event type,
// the event type can be any type such as std::string, int, etc.
// The second is the prototype of the listener.
eventpp::EventDispatcher<int, void ()> dispatcher;

// Add a listener. As the type of dispatcher,
// here 3 and 5 is the event type,
// []() {} is the listener.
// Lambda is not required, any function or std::function
// or whatever function object with the required prototype is fine.
dispatcher.appendListener(3, []() {
	std::cout << "Got event 3." << std::endl;
});
dispatcher.appendListener(5, []() {
	std::cout << "Got event 5." << std::endl;
});
dispatcher.appendListener(5, []() {
	std::cout << "Got another event 5." << std::endl;
});

// Dispatch the events, the first argument is always the event type.
dispatcher.dispatch(3);
dispatcher.dispatch(5);

// Add the folder *include* to include path.
#include "eventpp/callbacklist.h"

// The namespace is eventpp
// The callback list prototype has two parameters.
eventpp::CallbackList<void (const std::string &, const bool)> callbackList;

callbackList.append([](const std::string & s, const bool b) {
	std::cout << std::boolalpha << "Got callback 1, s is " << s << " b is " << b << std::endl;
});
// The callback prototype doesn't need to be exactly same as the callback list.
// It would be find as long as the arguments is compatible with the callbacklist.
callbackList.append([](std::string s, int b) {
	std::cout << std::boolalpha << "Got callback 2, s is " << s << " b is " << b << std::endl;
});

// Invoke the callback list
callbackList("Hello world", true);

• Event dispatcher
• Callback list
• Frequently Asked Questions
• There are compilable tutorials in the unit tests.

The library itself is header only and doesn't need building.
The unit test requires CMake to build, and there is a makefile to ease the building.
Go to folder tests/build, then run make with different target.

• make vc17 #generate solution files for Microsoft Visual Studio 2017, then open eventpptest.sln in folder project_vc17
• make vc15 #generate solution files for Microsoft Visual Studio 2015, then open eventpptest.sln in folder project_vc15
• make mingw #build using MinGW
• make linux #build on Linux

I (wqking) am a big fan of observer pattern (publish/subscribe pattern), I used such pattern a lot in my code. I either used GCallbackList in my cpgf library which is too simple and not safe, or repeated coding event dispatching mechanism such as I did in my Gincu game engine. Both approaches are neither fun nor robust.
Thanking to C++11, now it's quite easy to write a reusable event library with beautiful syntax (it's a nightmare to simulate the variadic template in C++03), so here comes eventpp.