Actually I find it confusing that user32.c DragDetect is in win.c and win32u one is in input.c. I still feel like drag-n-drop support does not really belong in input.c so I'd prefer to have both moved to window.c.
Ok.
Also, I don't know why but DragDetect has a user32 wrapper, and you've only added a forward import for DragObject. I think it'd be best to have a wrapper for it too if there's a reason why DragDetect has one.
I think it's because of argument differences.