iced is cool

2026-06-11T00:00:00+00:00

Being a racing driver means you are racing with other people. And if you no longer go for a gap that exists, you are no longer a racing driver. – Ayrton Senna </blockquote>
Preface</h2>
If you’ve spent any time looking at the Rust GUI landscape, you’ve probably heard of iced</code>. It has quickly become one of the most popular libraries for building native user interfaces in Rust, loved for its type-safety and declarative approach. In fact, it has matured enough to power entire desktop environments: System76 is building their next-generation COSMIC desktop environment completely on top of it.
Lately, I’ve been working on adding a native print dialog to the COSMIC desktop. Working on a project of this scale means getting comfortable with how iced</code> manages state, updates, and asynchronous background tasks.
To consolidate my own learning and give back to the community, I wanted to write about how iced</code> handles asynchronous background work. In this post, we’ll build a very basic system monitor app that tracks CPU usage in real-time. We’ll start with how iced</code> works at a high level and then build the application iteratively, diving deep into Subscriptions - the idiomatic way to handle streaming data in iced</code>.
How does iced work?</h2> If you come from the web world, you’re probably familiar with React, Vue, or Elm. If not, don’t worry. iced</code> is built entirely on the principles of The Elm Architecture (TEA). Instead of managing mutable UI nodes directly (like in GTK or Qt, where you hold references to widgets and call .set_text()</code> on them), iced</code> is completely declarative. It revolves around a simple, unidirectional loop made of four core concepts: State: The data of your application. For example, cpu_usage: f64</code>.</li> View: A function that describes how your state should be rendered. It takes your state and returns a tree of UI widgets.</li> Message: User interactions or background events that happen in your application (e.g., a button click, or a new CPU stat sample arriving).</li> Update: A function that takes your current State</code> and a Message</code>, updates the state accordingly, and tells iced</code> if we need to run any commands.</li> </ol> Whenever the state changes in the update</code> function, iced</code> automatically calls view</code> again, computes the difference, and redraws the UI.

~/ayu.ch - iced

iced is cool