glfw/glfw — pull request #171 by sagaceilo (2013-11-11 11:27:42+00:00)
Title: Parent window.

With that changes, GLFW is able to create a new windows that are always on top of another, just like in this screen :

http://i.imgur.com/QiL5k1l.png

Cocoa and X11 platforms need to be veryfied bcoz I dont have this OS'es to test.