For quite some time I am publishing so called Sciter.Lite version of Sciter Engine on the site and on GitHub.
Sciter.Lite allows to render UI defined as HTML/CSS and optionally script on surface GLFW windows. Sciter SDK has demo project of how to bind GLFW / OpenGL and Sciter.
Here is screenshot of that demo application:
Sciter supports layered output where pure OpenGL primitives rendering is sandwiched between background and foreground HTML/CSS layers. See this article and movie ( while it is about DirectX, with GLFW principles are the same).
In GLFW context Sciter can render its stuff as on OpenGL directly as on bitmap. Internally Sciter.Lite uses Skia as a graphics backend. And for the note “Big” Sciter can use DirectX/Direct2D, CoreGraphics (on Mac) and Cairo (on GTK).
For the note: Sciter API exposes sciter::graphics API, see: sciter-x-graphics.hpp ) for the cases when standard HTML/CSS rendering is not enough. So your native code can use this set of anti-aliased 2D rendering primitives directly.
Hope it will be useful for someone.