From 442d2d75d71bbc057e667edc301a79fa1cc813be Mon Sep 17 00:00:00 2001
From: rtk0c <mail.tianyig@gmail.com>
Date: Sat, 27 Mar 2021 23:01:07 -0700
Subject: Initial setup

---
 core/src/Utils/Sigslot.hpp | 150 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 150 insertions(+)
 create mode 100644 core/src/Utils/Sigslot.hpp

(limited to 'core/src/Utils/Sigslot.hpp')

diff --git a/core/src/Utils/Sigslot.hpp b/core/src/Utils/Sigslot.hpp
new file mode 100644
index 0000000..9aa5f4b
--- /dev/null
+++ b/core/src/Utils/Sigslot.hpp
@@ -0,0 +1,150 @@
+#pragma once
+
+#include "Utils/fwd.hpp"
+
+#include <cstddef>
+#include <functional>
+#include <span>
+#include <utility>
+#include <vector>
+
+class SignalStub {
+public:
+	/// Non-template interface for Signal<T...> to implement (a barrier to stop template
+	/// arguments propagation).
+	class IWrapper {
+	public:
+		virtual ~IWrapper() = default;
+		virtual void RemoveFunction(int id) = 0;
+	};
+
+	enum {
+		InvalidId = -1,
+	};
+
+	struct Connection {
+		SlotGuard* guard;
+		int slotId;
+		int id = InvalidId; // If `InvalidId`, then this "spot" is unused
+
+		bool IsOccupied() const;
+	};
+
+private:
+	std::vector<Connection> mConnections;
+	IWrapper* mWrapper;
+
+private:
+	template <class...>
+	friend class Signal;
+	friend class SlotGuard;
+
+	SignalStub(IWrapper& wrapper);
+	~SignalStub();
+
+	SignalStub(const SignalStub&) = delete;
+	SignalStub& operator=(const SignalStub&) = delete;
+	SignalStub(SignalStub&&) = default;
+	SignalStub& operator=(SignalStub&&) = default;
+
+	std::span<const Connection> GetConnections() const;
+	Connection& InsertConnection(SlotGuard* guard = nullptr);
+	void RemoveConnection(int id);
+	void RemoveConnectionFor(SlotGuard& guard);
+	void RemoveAllConnections();
+};
+
+template <class... TArgs>
+class Signal : public SignalStub::IWrapper {
+private:
+	// Must be in this order so that mFunctions is still intact when mStub's destructor runs
+	std::vector<std::function<void(TArgs...)>> mFunctions;
+	SignalStub mStub;
+
+public:
+	Signal()
+		: mStub(*this) {
+	}
+
+	virtual ~Signal() = default;
+
+	Signal(const Signal&) = delete;
+	Signal& operator=(const Signal&) = delete;
+	Signal(Signal&&) = default;
+	Signal& operator=(Signal&&) = default;
+
+	void operator()(TArgs... args) {
+		for (auto& conn : mStub.GetConnections()) {
+			if (conn.IsOccupied()) {
+				mFunctions[conn.id](std::forward<TArgs>(args)...);
+			}
+		}
+	}
+
+	template <class TFunction>
+	int Connect(TFunction slot) {
+		auto& conn = mStub.InsertConnection();
+		mFunctions.resize(std::max(mFunctions.size(), (size_t)conn.id + 1));
+		mFunctions[conn.id] = std::move(slot);
+		return conn.id;
+	}
+
+	template <class TFunction>
+	int Connect(SlotGuard& guard, TFunction slot) {
+		auto& conn = mStub.InsertConnection(&guard);
+		mFunctions.resize(std::max(mFunctions.size(), (size_t)conn.id + 1));
+		mFunctions[conn.id] = std::move(slot);
+		return conn.id;
+	}
+
+	void Disconnect(int id) {
+		mStub.RemoveConnection(id);
+	}
+
+	void DisconnectFor(SlotGuard& guard) {
+		mStub.RemoveConnectionFor(guard);
+	}
+
+	void DisconnectAll() {
+		mStub.RemoveAllConnections();
+	}
+
+	virtual void RemoveFunction(int id) {
+		mFunctions[id] = {};
+	}
+};
+
+/// Automatic disconnection mechanism for Signal<>.
+/// Bind connection to this guard by using the Connect(SlotGuard&, TFunction) overload.
+/// Either DisconnectAll() or the destructor disconnects all connections bound to this guard.
+class SlotGuard {
+private:
+	struct Connection {
+		SignalStub* stub = nullptr;
+		int stubId = SignalStub::InvalidId;
+	};
+	std::vector<Connection> mConnections;
+
+public:
+	friend class SignalStub;
+	SlotGuard();
+	~SlotGuard();
+
+	SlotGuard(const SlotGuard&) = delete;
+	SlotGuard& operator=(const SlotGuard&) = delete;
+	SlotGuard(SlotGuard&&) = default;
+	SlotGuard& operator=(SlotGuard&&) = default;
+
+	/// Disconnect all connection associated with this SlotGuard.
+	void DisconnectAll();
+
+private:
+	/// \return Slot id.
+	int InsertConnection(SignalStub& stub, int stubId);
+	/// Remove the connection data in this associated with slotId. This does not invoke
+	/// the connections' stub's RemoveConnection function.
+	void RemoveConnection(int slotId);
+	/// Disconnect all connections from the given stub associated with this SlotGuard.
+	/// Implementation for SignalStub::RemoveConnectionsFor(SlotGuard&)
+	void RemoveConnectionFor(SignalStub& stub);
+};
-- 
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