egui_web: Add simple fetch API and demostrate it in example_web

example_web/src/example_app.rs

@@ -1,15 +1,18 @@
-/// We derive Deserialize/Serialize so we can persist app state on shutdown.
-#[derive(serde::Deserialize, serde::Serialize)]
+use egui_web::fetch::Response;
+use std::sync::mpsc::Receiver;
+
 pub struct ExampleApp {
-    name: String,
-    age: u32,
+    url: String,
+    receivers: Vec<Receiver<Result<Response, String>>>,
+    fetch_result: Option<Result<Response, String>>,
 }
 
 impl Default for ExampleApp {
     fn default() -> Self {
         Self {
-            name: "Arthur".to_owned(),
-            age: 42,
+            url: "https://raw.githubusercontent.com/emilk/egui/master/README.md".to_owned(),
+            receivers: Default::default(),
+            fetch_result: Default::default(),
         }
     }
 }
@@ -20,30 +23,82 @@ impl egui::app::App for ExampleApp {
     fn ui(
         &mut self,
         ctx: &std::sync::Arc<egui::Context>,
-        integration_context: &mut egui::app::IntegrationContext,
+        _integration_context: &mut egui::app::IntegrationContext,
     ) {
-        let ExampleApp { name, age } = self;
-
-        // Example used in `README.md`.
         egui::CentralPanel::default().show(ctx, |ui| {
-            ui.heading("My Egui Application");
+            ui.heading("HTTP Get inside of Egui");
+            ui.add(egui::github_link_file!(
+                "https://github.com/emilk/egui/blob/master/",
+                "(source code)"
+            ));
 
-            ui.horizontal(|ui| {
-                ui.label("Your name: ");
-                ui.text_edit_singleline(name);
-            });
+            {
+                let mut trigger_fetch = false;
 
-            ui.add(egui::Slider::u32(age, 0..=120).text("age"));
-            if ui.button("Click each year").clicked {
-                *age += 1;
+                ui.horizontal(|ui| {
+                    ui.label("URL:");
+                    trigger_fetch |= ui.text_edit_singleline(&mut self.url).lost_kb_focus;
+
+                    if ui.button("Egui README.md").clicked {
+                        self.url = "https://raw.githubusercontent.com/emilk/egui/master/README.md"
+                            .to_owned();
+                    }
+                    if ui.button("Source code for this file").clicked {
+                        self.url =
+                            format!("https://raw.githubusercontent.com/emilk/egui/{}", file!());
+                    }
+                });
+                trigger_fetch |= ui.button("GET").clicked;
+
+                if trigger_fetch {
+                    let (sender, receiver) = std::sync::mpsc::channel();
+                    self.receivers.push(receiver);
+                    let url = self.url.clone();
+
+                    let future = async move {
+                        let result = egui_web::fetch::get_text(&url).await;
+                        sender.send(result).ok();
+                        // TODO: trigger egui repaint somehow
+                    };
+
+                    egui_web::spawn_future(future);
+                }
             }
 
-            ui.label(format!("Hello '{}', age {}", name, age));
-
-            ui.advance_cursor(16.0);
-            if ui.button("Quit").clicked {
-                integration_context.output.quit = true;
+            // Show finished download (if any):
+            if let Some(result) = &self.fetch_result {
+                ui.separator();
+                match result {
+                    Ok(response) => {
+                        ui_response(ui, response);
+                    }
+                    Err(error) => {
+                        // This should only happen if the fetch API isn't available or something similar.
+                        ui.add(egui::Label::new(error).text_color(egui::color::RED));
+                    }
+                }
             }
         });
+
+        for i in (0..self.receivers.len()).rev() {
+            if let Ok(result) = self.receivers[i].try_recv() {
+                self.fetch_result = Some(result);
+                let _ = self.receivers.swap_remove(i);
+            }
+        }
     }
 }
+
+fn ui_response(ui: &mut egui::Ui, response: &Response) {
+    ui.monospace(format!("url:         {}", response.url));
+    ui.monospace(format!(
+        "status:      {} ({})",
+        response.status, response.status_text
+    ));
+
+    ui.monospace("Body:");
+    ui.separator();
+    egui::ScrollArea::auto_sized().show(ui, |ui| {
+        ui.monospace(&response.body);
+    });
+}