util.hpp

#pragma once
#include <stdint.h>
 
// No point in documenting these macros. If people are trying to use them,
// they're doing something weird and I don't want to help them :)
// If you need to know what they do, look at how they're used.
 
#define VTABLE_FAKE_ENTRY(n, x) uint32_t fakeentry##x[n * 3]
 
template<typename TReturn, typename ...TArgs>
struct VTableFunction {
    int32_t offset;
    uint32_t unused;
    TReturn (*func)(void *self, TArgs...);
 
    TReturn operator()(void *self, TArgs... args) {
        void *self2 = reinterpret_cast<void *>(
            reinterpret_cast<uint8_t *>(self) + offset
        );
 
        return func(self2, args...);
    }
};
 
class Wrapped {
public:
    template <typename T>
    T *GetWrapped() {
        return static_cast<T *>(m_wrapped);
    }
 
protected:
    Wrapped() = default;
    ~Wrapped() = default;
 
    // Since we use the trick with the vtable to overide functions (@c .me), we
    // can't let the object's address change. Prevent that by deleting the copy
    // constructor and assignment operator.
    Wrapped(Wrapped const &) = delete;
    void operator=(Wrapped const &) = delete;
 
    void *m_wrapped;
};
 
class GUIElement : public Wrapped {};