SDL3-TestingSuite/SDL3/ImGuiUserData.cs

using System.Runtime.InteropServices;

namespace SDL3_TestingSuite.SDL3;

public unsafe static class ImGuiUserData<T> where T : class
{
    public static void* Store(T value)
    {
        if (value == null)
            return null;

        GCHandle handle = GCHandle.Alloc(value, GCHandleType.Normal);
        return (void*)GCHandle.ToIntPtr(handle);
    }

    public static T? Get(void* ptr)
    {
        if (ptr == null)
            return null;

        GCHandle handle = GCHandle.FromIntPtr((nint)ptr);
        return (T?)handle.Target;
    }

    public static void Free(void* ptr)
    {
        if (ptr == null)
            return;

        GCHandle handle = GCHandle.FromIntPtr((nint)ptr);

        if (handle.IsAllocated)
            handle.Free();
    }
}