internal: new shared_ptr and weak_ptr implementation (#5883)

moves std::shared_ptrs to a new implementation

Advantages:
- you can dereference a weak_ptr directly. This will obviously segfault on a nullptr deref if it's expired.
   - this is useful to avoid the .lock() hell where we are 100% sure the pointer _should_ be valid. (and if it isn't, it should throw.)
- weak_ptrs are still valid while the SP is being destroyed.
   - reasoning: while an object (e.g. CWindow) is being destroyed, its `weak_ptr self` should be accessible (the sp is still alive, and so is CWindow), but it's not because by stl it's already expired (to prevent resurrection)
   - this impl solves it differently. w_p is expired, but can still be dereferenced and used. Creating `s_p`s is not possible anymore, though.
   - this is useful in destructors and callbacks.

src/helpers/memory/SharedPtr.hpp

@@ -0,0 +1,300 @@
+#pragma once
+
+#include <typeinfo>
+#include <typeindex>
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+
+#define SP CSharedPointer
+
+/*
+    This is a custom impl of std::shared_ptr.
+    It is not thread-safe like the STL one,
+    but Hyprland is single-threaded anyways.
+
+    It differs a bit from how the STL one works,
+    namely in the fact that it keeps the T* inside the
+    control block, and that you can still make a CWeakPtr
+    or deref an existing one inside the destructor.
+*/
+namespace CSharedPointer_ {
+
+    class impl_base {
+      public:
+        virtual ~impl_base(){};
+
+        virtual void         inc() noexcept         = 0;
+        virtual void         dec() noexcept         = 0;
+        virtual void         incWeak() noexcept     = 0;
+        virtual void         decWeak() noexcept     = 0;
+        virtual unsigned int ref() noexcept         = 0;
+        virtual unsigned int wref() noexcept        = 0;
+        virtual void         destroy() noexcept     = 0;
+        virtual bool         destroying() noexcept  = 0;
+        virtual bool         dataNonNull() noexcept = 0;
+    };
+
+    template <typename T>
+    class impl : public impl_base {
+      public:
+        impl(T* data) noexcept : _data(data) {
+            ;
+        }
+
+        /* strong refcount */
+        unsigned int _ref = 0;
+        /* weak refcount */
+        unsigned int _weak = 0;
+
+        T*           _data = nullptr;
+
+        friend void  swap(impl*& a, impl*& b) {
+            impl* tmp = a;
+            a         = b;
+            b         = tmp;
+        }
+
+        /* if the destructor was called, 
+           creating shared_ptrs is no longer valid */
+        bool _destroying = false;
+
+        void _destroy() {
+            if (!_data)
+                return;
+
+            // first, we destroy the data, but keep the pointer.
+            // this way, weak pointers will still be able to
+            // reference and use, but no longer create shared ones.
+            _destroying = true;
+            __deleter(_data);
+            // now, we can reset the data and call it a day.
+            _data       = nullptr;
+            _destroying = false;
+        }
+
+        std::default_delete<T> __deleter{};
+
+        //
+        virtual void inc() noexcept {
+            _ref++;
+        }
+
+        virtual void dec() noexcept {
+            _ref--;
+        }
+
+        virtual void incWeak() noexcept {
+            _weak++;
+        }
+
+        virtual void decWeak() noexcept {
+            _weak--;
+        }
+
+        virtual unsigned int ref() noexcept {
+            return _ref;
+        }
+
+        virtual unsigned int wref() noexcept {
+            return _weak;
+        }
+
+        virtual void destroy() noexcept {
+            _destroy();
+        }
+
+        virtual bool destroying() noexcept {
+            return _destroying;
+        }
+
+        virtual bool dataNonNull() noexcept {
+            return _data;
+        }
+
+        virtual ~impl() {
+            destroy();
+        }
+    };
+};
+
+template <typename T>
+class CSharedPointer {
+  public:
+    template <typename X>
+    using validHierarchy = typename std::enable_if<std::is_assignable<T*, X*>::value>;
+
+    /* creates a new shared pointer managing a resource
+       avoid calling. Could duplicate ownership. Prefer makeShared */
+    explicit CSharedPointer(T* object) noexcept {
+        impl_ = new CSharedPointer_::impl<T>(object);
+        increment();
+    }
+
+    /* creates a shared pointer from a reference */
+    template <typename U, typename = validHierarchy<U>>
+    CSharedPointer(const CSharedPointer<U>& ref) noexcept {
+        impl_ = ref.impl_;
+        increment();
+    }
+
+    CSharedPointer(const CSharedPointer& ref) noexcept {
+        impl_ = ref.impl_;
+        increment();
+    }
+
+    template <typename U, typename = validHierarchy<U>>
+    CSharedPointer(CSharedPointer<U>&& ref) noexcept {
+        std::swap(impl_, ref.impl_);
+    }
+
+    CSharedPointer(CSharedPointer&& ref) noexcept {
+        std::swap(impl_, ref.impl_);
+    }
+
+    /* allows weakPointer to create from an impl */
+    CSharedPointer(CSharedPointer_::impl_base* implementation) noexcept {
+        impl_ = implementation;
+        increment();
+    }
+
+    /* creates an empty shared pointer with no implementation */
+    CSharedPointer() noexcept {
+        ; // empty
+    }
+
+    /* creates an empty shared pointer with no implementation */
+    CSharedPointer(std::nullptr_t) noexcept {
+        ; // empty
+    }
+
+    ~CSharedPointer() {
+        // we do not decrement here,
+        // because we want to preserve the pointer
+        // in case this is the last owner.
+        if (impl_ && impl_->ref() == 1)
+            destroyImpl();
+        else
+            decrement();
+    }
+
+    template <typename U, typename = validHierarchy<U>>
+    CSharedPointer<T>& operator=(const CSharedPointer<U>& rhs) {
+        if (impl_ == rhs.impl_)
+            return *this;
+
+        decrement();
+        impl_ = rhs.impl_;
+        increment();
+        return *this;
+    }
+
+    CSharedPointer& operator=(const CSharedPointer& rhs) {
+        if (impl_ == rhs.impl_)
+            return *this;
+
+        decrement();
+        impl_ = rhs.impl_;
+        increment();
+        return *this;
+    }
+
+    template <typename U, typename = validHierarchy<U>>
+    CSharedPointer<T>& operator=(CSharedPointer<U>&& rhs) {
+        std::swap(impl_, rhs.impl_);
+        return *this;
+    }
+
+    CSharedPointer& operator=(CSharedPointer&& rhs) {
+        std::swap(impl_, rhs.impl_);
+        return *this;
+    }
+
+    operator bool() const {
+        return impl_ && impl_->dataNonNull();
+    }
+
+    bool operator==(const CSharedPointer& rhs) const {
+        return impl_ == rhs.impl_;
+    }
+
+    bool operator()(const CSharedPointer& lhs, const CSharedPointer& rhs) const {
+        return (uintptr_t)lhs.impl_ < (uintptr_t)rhs.impl_;
+    }
+
+    bool operator<(const CSharedPointer& rhs) const {
+        return (uintptr_t)impl_ < (uintptr_t)rhs.impl_;
+    }
+
+    T* operator->() const {
+        return get();
+    }
+
+    T& operator*() const {
+        return *get();
+    }
+
+    void reset() {
+        decrement();
+        impl_ = nullptr;
+    }
+
+    T* get() const {
+        return (T*)(impl_ ? static_cast<CSharedPointer_::impl<T>*>(impl_)->_data : nullptr);
+    }
+
+    unsigned int strongRef() const {
+        return impl_ ? impl_->ref() : 0;
+    }
+
+    CSharedPointer_::impl_base* impl_ = nullptr;
+
+  private:
+    /* 
+       no-op if there is no impl_
+       may delete the stored object if ref == 0
+       may delete and reset impl_ if ref == 0 and weak == 0
+    */
+    void decrement() {
+        if (!impl_)
+            return;
+
+        impl_->dec();
+
+        // if ref == 0, we can destroy impl
+        if (impl_->ref() == 0)
+            destroyImpl();
+    }
+    /* no-op if there is no impl_ */
+    void increment() {
+        if (!impl_)
+            return;
+
+        impl_->inc();
+    }
+
+    /* destroy the pointed-to object 
+       if able, will also destroy impl */
+    void destroyImpl() {
+        // destroy the impl contents
+        impl_->destroy();
+
+        // check for weak refs, if zero, we can also delete impl_
+        if (impl_->wref() == 0) {
+            delete impl_;
+            impl_ = nullptr;
+        }
+    }
+};
+
+template <typename U, typename... Args>
+static CSharedPointer<U> makeShared(Args&&... args) {
+    return CSharedPointer<U>(new U(std::forward<Args>(args)...));
+}
+
+template <typename T>
+struct std::hash<CSharedPointer<T>> {
+    std::size_t operator()(const CSharedPointer<T>& p) const noexcept {
+        return std::hash<void*>{}(p->impl_);
+    }
+};