commit f313d1abbed0c7a3ba04a0b5c04826db5c1c1ab8
Author: Sara <sara@saragerretsen.nl>
Date:   Wed Apr 16 20:33:18 2025 +0200

    feat: added callabe and signal

diff --git a/callable.hpp b/callable.hpp
new file mode 100644
index 0000000..91e687c
--- /dev/null
+++ b/callable.hpp
@@ -0,0 +1,69 @@
+#ifndef CANVAS_CALLABLE_HPP
+#define CANVAS_CALLABLE_HPP
+
+#include <functional>
+#include <memory>
+
+namespace ce {
+/* Base interface template for a member function pointer object
+ */
+template <class Return, class... Args>
+struct HiddenCallableBase {
+    virtual ~HiddenCallableBase() = default;
+    virtual Return call(Args... args) const = 0;
+    virtual bool equals(HiddenCallableBase<Return, Args...> const &other) const;
+};
+
+template <class Return, class... Args> bool HiddenCallableBase<Return, Args...>::equals(HiddenCallableBase<Return, Args...> const &other) const {
+    return &other == this;
+}
+
+/* Hidden component of a Callable, specialized for a specific target object
+ */
+template <class Target, class Return, class... Args>
+struct HiddenCallable : public HiddenCallableBase<Return, Args...> {
+typedef Return (Target::*Signature)(Args...);
+    HiddenCallable(Target *target, Signature function);
+    Target *target{nullptr};
+    Signature function{nullptr};
+    virtual void call(Args...) const override;
+    virtual bool equals(HiddenCallableBase<Return, Args...> const &other) const override;
+};
+
+template <class Target, class Return, class... Args> bool HiddenCallable<Target, Return, Args...>::equals(HiddenCallableBase<Return, Args...> const &other) const {
+    HiddenCallable<Target, Return, Args...> const *cast{dynamic_cast<HiddenCallable<Target, Return, Args...> const *>(&other)};
+    return cast != nullptr && &other == this && cast->target == this->target && cast->function == this->function;
+}
+
+template <class Target, class Return, class... Args> HiddenCallable<Target, Return, Args...>::HiddenCallable(Target *target, Signature function) : target{target}, function{function} {}
+template <class Target, class Return, class... Args> void HiddenCallable<Target, Return, Args...>::call(Args... args) const {
+    std::invoke(this->function, this->target, args...);
+}
+
+/* Class for referring to a callable pointer to a member function.
+ */
+template <class Return, class... Args>
+class Callable {
+public:
+    std::shared_ptr<HiddenCallableBase<Return, Args...> const> hidden;
+    template <class Target> static Callable<Return, Args...> make(Target *target, Return (Target::*function)(Args...));
+    Return call(Args... args);
+};
+
+template <class Return, class... Args> template <class Target> Callable<Return, Args...>
+Callable<Return, Args...>::make(Target *target, Return (Target::*function)(Args...)) {
+    Callable<Return, Args...> callable;
+    callable.hidden = std::make_unique<HiddenCallable<Target, Return, Args...>>(target, function);
+    return callable;
+};
+
+template <class Return, class... Args> Return Callable<Return, Args...>::call(Args... args) {
+    return this->hidden->call(args...);
+}
+
+template <class Return, class... Args> bool operator==(Callable<Return, Args...> const &lhs, Callable<Return, Args...> const &rhs) {
+    return lhs.hidden->equals(*rhs.hidden.get());
+}
+}
+
+#endif // !CANVAS_CALLABLE_HPP
diff --git a/signal.hpp b/signal.hpp
new file mode 100644
index 0000000..8acc3f0
--- /dev/null
+++ b/signal.hpp
@@ -0,0 +1,65 @@
+#ifndef CANVAS_SIGNAL_HPP
+#define CANVAS_SIGNAL_HPP
+
+#include "callable.hpp"
+#include <cstdio>
+#include <vector>
+
+namespace ce {
+/*! Observer-listener implementation
+ */
+template <class... Args>
+class Signal {
+    std::vector<Callable<void, Args...>> listeners{};
+public:
+    void connect(Callable<void, Args...> callable);
+    void disconnect(Callable<void, Args...> callable);
+    void invoke(Args...);
+};
+
+template <class... Args> void Signal<Args...>::connect(Callable<void, Args...> callable) {
+    this->listeners.push_back(callable);
+}
+
+template <class... Args> void Signal<Args...>::disconnect(Callable<void, Args...> callable) {
+    std::erase_if(this->listeners,
+    [&callable](Callable<void, Args...> &listener) -> bool {
+        return listener == callable;
+    });
+}
+
+template <class... Args> void Signal<Args...>::invoke(Args... args) {
+    for(Callable<void, Args...> &listener : this->listeners) {
+        listener.call(args...);
+    }
+}
+
+#ifdef DEBUG
+static inline
+void TEST_signals() {
+    struct A {inline void f(int val) {
+        std::printf("A: %d\n", val);
+    }};
+    struct B { inline void f(int val) {
+        std::printf("B: %d\n", val);
+    }};
+
+    A a_object;
+    B b_object;
+
+    Signal<int> signal;
+
+    Callable<void, int> a_callable{Callable<void, int>::make(&a_object, &A::f)};
+    Callable<void, int> b_callable{Callable<void, int>::make(&b_object, &B::f)};
+
+    signal.connect(a_callable);
+    signal.invoke(5);
+    signal.connect(b_callable);
+    signal.invoke(12);
+    signal.disconnect(a_callable);
+    signal.invoke(10);
+}
+#endif
+}
+
+#endif // !CANVAS_SIGNAL_HPP