How to dynamically update winit CSD light/dark theme just like Iced UI theme?

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1

Iced apps can respond to dynamic OS theme changes using dark-light cross-platform crate and Iced Subscription, for example:

impl App {
    fn update(&mut self, message: Message) {
        match message {
            AppMsg::ThemeSelected(theme) => {
                self.theme = theme;
            }
        }
    }

    fn subscription(&self) -> Subscription<Message> {
        Subscription::run(|| {
            let stream = futures::executor::block_on(dark_light::subscribe())
                .map(|s| s.boxed())
                .unwrap_or(futures::stream::empty().boxed());

            stream
                .map(|color_mode| match color_mode {
                    dark_light::Mode::Default | dark_light::Mode::Light => Theme::Light,
                    dark_light::Mode::Dark => Theme::Dark,
                })
                .map(|theme| Message::ThemeChanged(theme))
        })
    }

    fn theme(&self) -> Theme {
        self.theme.clone()
    }
}

However, unlike the iced-drawn UI, the winit-drawn UI (titlebar, border, etc.) do not respond to dynamic OS color theme changes. Notably, the capability is present in winit, because it gets drawn with correct light/dark color at app launch, but stays stuck afterwards. This makes sense, I guess, as our setup does not hook into winit at all.

I noticed that winit provides Window::set_theme API, which doesn’t seem to be exposed by iced. If it could be exposed, then thanks to dark-light crate, we could trigger the winit CSD (client-side decoration) theme change from iced Application.