book: Extend main loop chapter with async section (#1511)

* book: Extend main loop chapter with async section

* Update book/listings/main_event_loop/7/main.rs

Co-authored-by: Bilal Elmoussaoui <[email protected]>

* book: Fix typo

* book: Add tokio and reqwest listing

* book: Fix app ids

* book: Add filenames

* Explain spawn_blocking in async context and ashpd

* book: Add example that reqwest fails without tokio

* book: Start with conclusion

* book: Move to async-channel for reqwest demo

* book: Add section about tokio

* book: Add main_event_loop_1 video

* book: Extend chapter

* book: Address Sabrina's comments

* Apply suggestions from @felinira's code review

Co-authored-by: Fina <[email protected]>

* Update book/src/main_event_loop.md

Co-authored-by: Fina <[email protected]>

---------

Co-authored-by: Bilal Elmoussaoui <[email protected]>
Co-authored-by: Fina <[email protected]>

Author: 3 people

book/listings/Cargo.lock

@@ -15,6 +15,9 @@ xshell = "0.2"
 dirs = "5.0"
 walkdir = "2.3"
 async-channel = "1.9.0"
+ashpd = { version = "0.6.2", features = ["gtk4"] }
+tokio = { version = "1.33.0", features = ["rt-multi-thread"] }
+reqwest = { version = "0.11", default-features = false, features = ["rustls-tls"] }
 
 [build-dependencies]
 glib-build-tools = "0.18"
@@ -206,6 +209,22 @@ path = "main_event_loop/4/main.rs"
 name = "main_event_loop_5"
 path = "main_event_loop/5/main.rs"
 
+[[bin]]
+name = "main_event_loop_6"
+path = "main_event_loop/6/main.rs"
+
+[[bin]]
+name = "main_event_loop_7"
+path = "main_event_loop/7/main.rs"
+
+[[bin]]
+name = "main_event_loop_8"
+path = "main_event_loop/8/main.rs"
+
+[[bin]]
+name = "main_event_loop_9"
+path = "main_event_loop/9/main.rs"
+
 # saving_window_state
 [[bin]]
 name = "saving_window_state_1"

book/listings/Cargo.toml

@@ -0,0 +1,61 @@
+use glib::{clone, MainContext};
+use gtk::prelude::*;
+use gtk::{gio, glib};
+use gtk::{Application, ApplicationWindow, Button};
+use std::thread;
+use std::time::Duration;
+
+const APP_ID: &str = "org.gtk_rs.MainEventLoop6";
+
+fn main() -> glib::ExitCode {
+    // Create a new application
+    let app = Application::builder().application_id(APP_ID).build();
+
+    // Connect to "activate" signal of `app`
+    app.connect_activate(build_ui);
+
+    // Run the application
+    app.run()
+}
+
+fn build_ui(app: &Application) {
+    // Create a button
+    let button = Button::builder()
+        .label("Press me!")
+        .margin_top(12)
+        .margin_bottom(12)
+        .margin_start(12)
+        .margin_end(12)
+        .build();
+
+    // ANCHOR: callback
+    // Connect to "clicked" signal of `button`
+    button.connect_clicked(move |button| {
+        let main_context = MainContext::default();
+        // The main loop executes the asynchronous block
+        main_context.spawn_local(clone!(@weak button => async move {
+            // Deactivate the button until the operation is done
+            button.set_sensitive(false);
+            let enable_button = gio::spawn_blocking(move || {
+                let ten_seconds = Duration::from_secs(10);
+                thread::sleep(ten_seconds);
+                true
+            })
+            .await
+            .expect("Task needs to finish successfully.");
+            // Set sensitivity of button to `enable_button`
+            button.set_sensitive(enable_button);
+        }));
+    });
+    // ANCHOR_END: callback
+
+    // Create a window
+    let window = ApplicationWindow::builder()
+        .application(app)
+        .title("My GTK App")
+        .child(&button)
+        .build();
+
+    // Present window
+    window.present();
+}

book/listings/main_event_loop/6/main.rs

@@ -0,0 +1,64 @@
+use ashpd::desktop::account::UserInformation;
+use ashpd::WindowIdentifier;
+use glib::{clone, MainContext};
+use gtk::prelude::*;
+use gtk::{glib, Application, ApplicationWindow, Button};
+
+const APP_ID: &str = "org.gtk_rs.MainEventLoop7";
+
+fn main() -> glib::ExitCode {
+    // Create a new application
+    let app = Application::builder().application_id(APP_ID).build();
+
+    // Connect to "activate" signal of `app`
+    app.connect_activate(build_ui);
+
+    // Run the application
+    app.run()
+}
+
+fn build_ui(app: &Application) {
+    // Create a button
+    let button = Button::builder()
+        .label("Press me!")
+        .margin_top(12)
+        .margin_bottom(12)
+        .margin_start(12)
+        .margin_end(12)
+        .build();
+
+    // ANCHOR: callback
+    // Connect to "clicked" signal of `button`
+    button.connect_clicked(move |button| {
+        let main_context = MainContext::default();
+        // The main loop executes the asynchronous block
+        main_context.spawn_local(clone!(@weak button => async move {
+            // Get native of button for window identifier
+            let native = button.native().expect("Need to be able to get native.");
+            // Get window identifier so that the dialog will be modal to the main window
+            let identifier = WindowIdentifier::from_native(&native).await;
+            let request = UserInformation::request()
+                .reason("App would like to access user information.")
+                .identifier(identifier)
+                .send()
+                .await;
+
+            if let Ok(response) = request.and_then(|r| r.response()) {
+                println!("User name: {}", response.name());
+            } else {
+                println!("Could not access user information.")
+            }
+        }));
+    });
+    // ANCHOR_END: callback
+
+    // Create a window
+    let window = ApplicationWindow::builder()
+        .application(app)
+        .title("My GTK App")
+        .child(&button)
+        .build();
+
+    // Present window
+    window.present();
+}

book/listings/main_event_loop/7/main.rs

@@ -0,0 +1,63 @@
+use glib::{clone, MainContext};
+use gtk::glib;
+use gtk::prelude::*;
+use gtk::{Application, ApplicationWindow, Button};
+
+const APP_ID: &str = "org.gtk_rs.MainEventLoop8";
+
+fn main() -> glib::ExitCode {
+    // Create a new application
+    let app = Application::builder().application_id(APP_ID).build();
+
+    // Connect to "activate" signal of `app`
+    app.connect_activate(build_ui);
+
+    // Run the application
+    app.run()
+}
+
+fn build_ui(app: &Application) {
+    // Create a button
+    let button = Button::builder()
+        .label("Press me!")
+        .margin_top(12)
+        .margin_bottom(12)
+        .margin_start(12)
+        .margin_end(12)
+        .build();
+
+    // ANCHOR: callback
+    let (sender, receiver) = async_channel::bounded(1);
+    // Connect to "clicked" signal of `button`
+    button.connect_clicked(move |_| {
+        let main_context = MainContext::default();
+        // The main loop executes the asynchronous block
+        main_context.spawn_local(clone!(@strong sender => async move {
+            let response = reqwest::get("https://www.gtk-rs.org").await;
+            sender.send(response).await.expect("The channel needs to be open.");
+        }));
+    });
+
+    let main_context = MainContext::default();
+    // The main loop executes the asynchronous block
+    main_context.spawn_local(clone!(@weak button => async move {
+        while let Ok(response) = receiver.recv().await {
+            if let Ok(response) = response {
+                println!("Status: {}", response.status());
+            } else {
+                println!("Could not make a `GET` request.");
+            }
+        }
+    }));
+    // ANCHOR_END: callback
+
+    // Create a window
+    let window = ApplicationWindow::builder()
+        .application(app)
+        .title("My GTK App")
+        .child(&button)
+        .build();
+
+    // Present window
+    window.present();
+}

book/listings/main_event_loop/8/main.rs

@@ -0,0 +1,67 @@
+use glib::{clone, MainContext};
+use gtk::glib;
+use gtk::prelude::*;
+use gtk::{Application, ApplicationWindow, Button};
+use once_cell::sync::Lazy;
+use tokio::runtime::Runtime;
+
+// ANCHOR: tokio_runtime
+const APP_ID: &str = "org.gtk_rs.MainEventLoop9";
+static RUNTIME: Lazy<Runtime> =
+    Lazy::new(|| Runtime::new().expect("Setting up tokio runtime needs to succeed."));
+
+fn main() -> glib::ExitCode {
+    // Create a new application
+    let app = Application::builder().application_id(APP_ID).build();
+
+    // Connect to "activate" signal of `app`
+    app.connect_activate(build_ui);
+
+    // Run the application
+    app.run()
+}
+// ANCHOR_END: tokio_runtime
+
+fn build_ui(app: &Application) {
+    // Create a button
+    let button = Button::builder()
+        .label("Press me!")
+        .margin_top(12)
+        .margin_bottom(12)
+        .margin_start(12)
+        .margin_end(12)
+        .build();
+
+    // ANCHOR: callback
+    let (sender, receiver) = async_channel::bounded(1);
+    // Connect to "clicked" signal of `button`
+    button.connect_clicked(move |_| {
+        RUNTIME.spawn(clone!(@strong sender => async move {
+            let response = reqwest::get("https://www.gtk-rs.org").await;
+            sender.send(response).await.expect("The channel needs to be open.");
+        }));
+    });
+
+    let main_context = MainContext::default();
+    // The main loop executes the asynchronous block
+    main_context.spawn_local(clone!(@weak button => async move {
+        while let Ok(response) = receiver.recv().await {
+            if let Ok(response) = response {
+                println!("Status: {}", response.status());
+            } else {
+                println!("Could not make a `GET` request.");
+            }
+        }
+    }));
+    // ANCHOR_END: callback
+
+    // Create a window
+    let window = ApplicationWindow::builder()
+        .application(app)
+        .title("My GTK App")
+        .child(&button)
+        .build();
+
+    // Present window
+    window.present();
+}