As we have already seen, the APIs exposed by the gtk crate can be a bit uncomfortable to write complex GUIs with. Fortunately, we have a wrapper crate called relm. The relm crate is inspired by the Elm language's architecture of Model-View-Update, which provides a simplistic approach for building reactive GUIs. Apart from relm, there are many other standalone GUI toolkits and crates in the works by the Rust community. One of the new and promising ones is Azul, which can be found at https://azul.rs/. It is a functional GUI framework that supports async I/O, along with features such as two-way data binding, which allows you to build reactive widgets and employs the principle of composition for building widgets, as opposed to the object-oriented model, which we explored in the gtk framework when building hews. As the rendering backend, Azul uses the performant Webrender rendering engine that's used in Servo from Mozilla.

Other notable mentions are conrod from the Piston Developers organization at https://github.com/PistonDevelopers/conrod, and imgui-rs at https://github.com/Gekkio/imgui-rs, which is a bindings library for the popular immediate mode ImGUI framework in C++.