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I am absolutely new to rust development so I apologize if this is too obvious to be added to the manual but it took me some time to figure out why the style of my adw widgets were wrong :)

It would be nice to have some guidance on best practices regarding state sharing between Relm4 components. These are the options I've considered so far:

• Introduce global state using SharedState. This is relatively easily to implement but may make it harder to write isolated automated tests. The tab_game example uses this approach.
• Pass down references to child components. I tried this at some point and got stuck trying to express the lifetime constraints.
• Perhaps passing down RefCell/RefMut variables could work. Haven't tried this yet. It may sidestep lifetime issues but could introduce runtime panics if not managed properly.
• Rely fully on message passing as opposed to shared state. This may be elaborate to maintain especially if there's a big hierarchy in your components.

May be somebody can help me understanding this sentence better:

If there is already an implementation for every type, why do I need to implement one?

The explanation of "Your first app" at https://relm4.org/book/stable/first_app.html still describes how to use Relm4 at version 0.4 instead of 0.5. It also links to a full example code on github, but it is written for 0.5 - https://github.com/Relm4/Relm4/blob/main/examples/simple_manual.rs

https://relm4.org/book/next/components.html#message-handling

.forward(&sender.input,

input is not a property of ComponentSender.