As far as I'm concerned, there is nothing directly available API in Win32 to implement this, it is usually made up of framework wrappers (such as MFC... ) implementation.
If you want to try to achieve this effect without MFC. I suggest you could try to use UI Automation to implement control patterns.
I suggest you could follow the following Docs:
Implementing UI Automation Control Patterns
Dock Control Pattern
Drag Control Pattern
DropTarget Control Pattern