How can I create a freeform window?

Question

User interface

Suppose I need to create a round/triangular/polygonal window. I know that something similar can be done on winapi. Are there other ways? Maybe some libraries can do this?

Answer 1

Create a window with a transparent background and no border - congratulations, you're great. In the end, everything is done through WinAPI on Windows, but almost any framework allows you to create a window with such properties.