egui/example_glium/src/main.rs

use egui_glium::{storage::FileStorage, RunMode};

/// We dervive Deserialize/Serialize so we can persist app state on shutdown.
#[derive(Default, serde::Deserialize, serde::Serialize)]
struct MyApp {
    counter: u64,
}

impl egui::app::App for MyApp {
    /// This function will be called whenever the Ui needs to be shown,
    /// which may be many times per second.
    fn ui(&mut self, ui: &mut egui::Ui, _: &mut dyn egui::app::Backend) {
        if ui.button("Increment").clicked {
            self.counter += 1;
        }
        if ui.button("Reset").clicked {
            self.counter = 0;
        }
        ui.label(format!("Counter: {}", self.counter));
    }

    fn on_exit(&mut self, storage: &mut dyn egui::app::Storage) {
        egui::app::set_value(storage, egui::app::APP_KEY, self);
    }
}

fn main() {
    let title = "My Egui Window";
    let storage = FileStorage::from_path(".egui_example_glium.json".into()); // Where to persist app state
    let app: MyApp = egui::app::get_value(&storage, egui::app::APP_KEY).unwrap_or_default(); // Restore `MyApp` from file, or create new `MyApp`.
    egui_glium::run(title, RunMode::Reactive, storage, app);
}