Examples: async request no blocking main thread

examples/Cargo.toml

@@ -13,6 +13,11 @@ glow = { version = "0.13.0", optional = true }
 epoxy = { version = "0.1.0", optional = true }
 libloading = { version = "0.8.0", optional = true }
 im-rc = { version = "15", optional = true }
+async-channel = { version = "2.1.1", optional = true }
+tokio = { version = "1", features = ["full"], optional = true }
+reqwest = { version = "0.11", features = ["json", "rustls-tls"], default-features = false, optional = true }
+serde = { version = "1.0", features = ["derive"], optional = true }
+
 gtk.workspace = true
 
 # used by gif-paintable example
@@ -26,6 +31,7 @@ optional = true
 default = []
 femtovg-support = ["epoxy", "femtovg", "glow", "libloading"]
 glium-support = ["glium", "epoxy", "libloading"]
+tokio = ["dep:tokio", "async-channel", "reqwest", "serde"]
 v4_10 = ["gtk/v4_10"]
 v4_12 = ["gtk/v4_12"]
 v4_14 = ["gtk/v4_14"]
@@ -192,6 +198,11 @@ name = "text_viewer"
 path = "text_viewer/main.rs"
 required-features = ["v4_10"]
 
+[[bin]]
+name = "tokio_async_request"
+path = "tokio_async_request/main.rs"
+required-features = ["tokio"]
+
 [[bin]]
 name = "video_player"
 path = "video_player/main.rs"

examples/README.md

@@ -47,5 +47,6 @@ cargo run --bin basics
 - [Squares](./squares/)
 - [Squeezer Bin](./squeezer_bin/)
 - [TextView](./text_viewer/)
+- [Tokio Async Request](./tokio_async_request/)
 - [Video Player](./video_player/)
 - [Virtual Methods](./virtual_methods/)

examples/tokio_async_request/README.md

@@ -0,0 +1,5 @@
+# Tokio async request
+
+This example shows an infinite list of pokemon names, whenever it reaches the end, it searches for new names and fills the list without blocking the main thread of the program.
+
+![Screenshot](screenshot.gif)

examples/tokio_async_request/main.rs

@@ -0,0 +1,110 @@
+use glib::clone;
+use gtk::prelude::*;
+use gtk::{glib, Application, ApplicationWindow};
+use serde::Deserialize;
+use std::sync::OnceLock;
+use tokio::runtime::Runtime;
+
+#[derive(Deserialize, Debug)]
+pub struct Pokemon {
+    pub name: String,
+}
+
+#[derive(Deserialize, Debug)]
+pub struct ResultBody {
+    results: Vec<Pokemon>,
+}
+
+#[derive(Debug)]
+pub struct PokemonClient {
+    page: u32,
+}
+
+impl Default for PokemonClient {
+    fn default() -> Self {
+        Self { page: 0 }
+    }
+}
+
+impl PokemonClient {
+    const URI: &'static str = "https://pokeapi.co/api/v2/pokemon";
+    const PAGE_LIMIT: &'static str = "100";
+
+    pub async fn get_pokemon_list(&mut self) -> Result<Vec<Pokemon>, reqwest::Error> {
+        let current_offset = self.page.to_string();
+        let params: [(&str, &str); 2] = [
+            ("limit", Self::PAGE_LIMIT),
+            ("offset", current_offset.as_str()),
+        ];
+        let url = reqwest::Url::parse_with_params(Self::URI, params).unwrap();
+        let body = reqwest::get(url).await?.json::<ResultBody>().await?;
+
+        self.page += 10;
+        Ok(body.results)
+    }
+}
+
+fn runtime() -> &'static Runtime {
+    static RUNTIME: OnceLock<Runtime> = OnceLock::new();
+    RUNTIME.get_or_init(|| Runtime::new().expect("Setting up tokio runtime needs to succeed."))
+}
+
+fn main() -> glib::ExitCode {
+    let app = Application::builder()
+        .application_id("org.gtk_rs.pokemon.list")
+        .build();
+    app.connect_activate(build_ui);
+    app.run()
+}
+
+fn build_ui(app: &Application) {
+    let (sender, receiver) = async_channel::bounded::<Result<Vec<Pokemon>, reqwest::Error>>(1);
+    runtime().spawn(clone!(@strong sender => async move {
+        let mut pokemon_client = PokemonClient::default();
+        let pokemon_vec = pokemon_client.get_pokemon_list().await;
+        sender.send(pokemon_vec).await.expect("The channel needs to be open.");
+    }));
+
+    let list_box = gtk::ListBox::builder().build();
+    let scrolled_window = gtk::ScrolledWindow::builder()
+        .hscrollbar_policy(gtk::PolicyType::Never)
+        .min_content_width(360)
+        .child(&list_box)
+        .build();
+
+    scrolled_window.connect_edge_reached(move |_, position| {
+        let mut pokemon_client = PokemonClient::default();
+        if gtk::PositionType::Bottom == position {
+            runtime().spawn(clone!(@strong sender => async move {
+                let pokemon_vec = pokemon_client.get_pokemon_list().await;
+                sender.send(pokemon_vec).await.expect("The channel needs to be open.");
+            }));
+        }
+    });
+
+    glib::spawn_future_local(async move {
+        while let Ok(response) = receiver.recv().await {
+            match response {
+                Ok(response) => {
+                    for pokemon in response {
+                        let label = gtk::Label::new(Some(&pokemon.name));
+                        label.set_halign(gtk::Align::Start);
+                        list_box.append(&label);
+                    }
+                }
+                Err(_) => {
+                    println!("bad request");
+                }
+            }
+        }
+    });
+
+    let window = ApplicationWindow::builder()
+        .application(app)
+        .title("Tokio integration")
+        .default_width(600)
+        .default_height(300)
+        .child(&scrolled_window)
+        .build();
+    window.present();
+}