The "Borland flood fill" routine that Microsoft was trying to beat was in the very popular (at the time) "Turbo Graphics for Borland" package which had an immensely useful stack of graphics primitives, some a little more advanced than what was available in Windows at the time, for pure DOS mode.

It was an awesome package - I shipped many products which used it in that era - and it was always a bit amusing to me that it seemed like Borland had almost everything they needed to write an operating system. But, they didn't.