[nrr]

The irony is that Acorn's RISC OS arguably came the closest to this ideal with any pragmatism. The way that file choosers worked effectively allowed one to pipe a saved file from one application to another and then do it again through the same workflow in the next application and so on.

[foul]

This kind of IPC lurks in every major OS, drag to an app window is supported by Xorg Mac and Windows.

[nrr]

I suppose this is IPC in the loosest possible sense? It's more like GetOpenFileName() and GetSaveFileName() in Win32 but getting handed a HANDLE outright instead of an LPCSTR to pass to CreateFile() later.