Yep. That was called DDE and is still used by a few minor things. https://learn.microsoft.com/en-us/windows/win32/dataxchg/about-dynamic-data-exchange https://

Yep. That was called DDE and is still used by a few minor things. https://learn.microsoft.com/en-us/windows/win32/dataxchg/about-dynamic-data-exchange https://learn.microsoft.com/en-us/windows/win32/dataxchg/abo... COM (ab)uses window messages primarily for objects with thread affinity. Microsoft don't (didn't?) have a standard way to post lambdas to a thread's message loop like most platforms do, so they hack it by using GUI messages to a hidden window.