Derive PartialOrd for enums

[otiv-wannes-vanleemput]

Hi!

First of all, loving the combination of Slint components states and enums.
What would be a nice to have though, is an implementation of PartialOrd for the Rust equivalent of the enums. This could be a use case:

Slint file:

export enum UIState {
    startup-state-one,
    startup-state-two,
    main-state-one,
    main-state-two
    
    
export Application inherits Window {
    in-out property <UIState> ui_state;
}

Rust file:

fn check_startup_state(slint_app: Application) {
    if are_requisites_for_startup_state_one_fulfilled() {
        if slint_app.get_ui_state() < UIState::MainStateOne {
            slint_app.set_ui_state(UIState::StartupStateOne);
        }
    }

This way, you don't have to check explicitly what state the enum variable is in.

[ogoffart]

There is this (not well documented) feature to add rust attributes to struct and enum with @rust-attr:

@rust-attr(derive(PartialOrd))
export enum UIState {
    startup-state-one,
    startup-state-two,
    main-state-one,
    main-state-two
}