dolphin/Source/Core/Common/HookableEvent.h
2023-03-06 00:12:26 +13:00

115 lines
3 KiB
C++

// Copyright 2023 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once
#include "Common/Logging/Log.h"
#include "Common/StringLiteral.h"
#include <functional>
#include <memory>
#include <mutex>
#include <string>
#include <string_view>
#include <vector>
namespace Common
{
struct HookBase
{
virtual ~HookBase() = default;
protected:
HookBase() = default;
// This shouldn't be copied. And since we always wrap it in unique_ptr, no need to move it either
HookBase(const HookBase&) = delete;
HookBase(HookBase&&) = delete;
HookBase& operator=(const HookBase&) = delete;
HookBase& operator=(HookBase&&) = delete;
};
// EventHook is a handle a registered listener holds.
// When the handle is destroyed, the HookableEvent will automatically remove the listener.
using EventHook = std::unique_ptr<HookBase>;
// A hookable event system.
//
// Define Events in a header as:
//
// using MyLoveyEvent = HookableEvent<"My lovely event", std::string, u32>;
//
// Register listeners anywhere you need them as:
// EventHook myHook = MyLoveyEvent::Register([](std::string foo, u32 bar) {
// fmt::print("I've been triggered with {} and {}", foo, bar)
// }, "NameOfHook");
//
// The hook will be automatically unregistered when the EventHook object goes out of scope.
// Trigger events by calling Trigger as:
//
// MyLoveyEvent::Trigger("Hello world", 42);
//
template <StringLiteral EventName, typename... CallbackArgs>
class HookableEvent
{
public:
using CallbackType = std::function<void(CallbackArgs...)>;
private:
struct HookImpl final : public HookBase
{
~HookImpl() override { HookableEvent::Remove(this); }
HookImpl(CallbackType callback, std::string name)
: m_fn(std::move(callback)), m_name(std::move(name))
{
}
CallbackType m_fn;
std::string m_name;
};
struct Storage
{
std::mutex m_mutex;
std::vector<HookImpl*> m_listeners;
};
// We use the "Construct On First Use" idiom to avoid the static initialization order fiasco.
// https://isocpp.org/wiki/faq/ctors#static-init-order
static Storage& GetStorage()
{
static Storage storage;
return storage;
}
static void Remove(HookImpl* handle)
{
auto& storage = GetStorage();
std::lock_guard lock(storage.m_mutex);
std::erase(storage.m_listeners, handle);
}
public:
// Returns a handle that will unregister the listener when destroyed.
[[nodiscard]] static EventHook Register(CallbackType callback, std::string name)
{
auto& storage = GetStorage();
std::lock_guard lock(storage.m_mutex);
DEBUG_LOG_FMT(COMMON, "Registering {} handler at {} event hook", name, EventName.value);
auto handle = std::make_unique<HookImpl>(callback, std::move(name));
storage.m_listeners.push_back(handle.get());
return handle;
}
static void Trigger(const CallbackArgs&... args)
{
auto& storage = GetStorage();
std::lock_guard lock(storage.m_mutex);
for (const auto& handle : storage.m_listeners)
handle->m_fn(args...);
}
};
} // namespace Common