I am working on the IUP fork (UI toolkit) , with many new drivers/backends and features, and, of course, I added Haiku because it looks and performs so well, it works differently from what I used to see, making it even more interesting. The result: the absolute king in memory usage was the Win32 driver, like 4M for Hello World; in Haiku, that is 3M! For comparison, the GTK4 driver uses 40M; GTK3 and Qt6 ~15. WinUI is something like ~25.