This is Nuklear UI subsystem for Urho3D.
nuklear.h
Urho3D
(obviously)
Place initialization code in your Application::Start()
auto nuklear = new NuklearUI(context_);
context_->RegisterSubsystem(nuklear);
// Initialize default font of your choice or use default one.
nuklear->GetFontAtlas()->default_font = nk_font_atlas_add_default(nuklear->GetFontAtlas(), 13.f, 0);
// Additional font initialization here. See https://github.com/vurtun/nuklear/blob/master/demo/sdl_opengl3/main.c
nuklear->FinalizeFonts();