Improve `download_progress` example

- Use `reqwest` with `Response::chunk` to notify progress.
- Turn example state into an enum

3 files changed, 117 insertions, 114 deletions

diff --git a/examples/download_progress/Cargo.toml b/examples/download_progress/Cargo.toml
index ce0435fd..34e6a132 100644
--- a/examples/download_progress/Cargo.toml
+++ b/examples/download_progress/Cargo.toml
@@ -6,8 +6,7 @@ edition = "2018"
 publish = false
 
 [dependencies]
-iced = { path = "../.." }
+iced = { path = "../..", features = ["tokio"] }
 iced_native = { path = "../../native" }
 iced_futures = { path = "../../futures" }
-async-std = { version = "1.0", features = ["unstable"] }
-isahc = "0.9.1"
+reqwest = "0.10"
diff --git a/examples/download_progress/src/downloader.rs b/examples/download_progress/src/downloader.rs
index 62f943fd..3b54341e 100644
--- a/examples/download_progress/src/downloader.rs
+++ b/examples/download_progress/src/downloader.rs
@@ -1,7 +1,7 @@
 use iced_futures::futures;
 
 // Just a little utility function
-pub fn file<T: ToString>(url: T) -> iced::Subscription<DownloadMessage> {
+pub fn file<T: ToString>(url: T) -> iced::Subscription<Progress> {
     iced::Subscription::from_recipe(Downloader {
         url: url.to_string(),
     })
@@ -16,7 +16,7 @@ impl<H, I> iced_native::subscription::Recipe<H, I> for Downloader
 where
     H: std::hash::Hasher,
 {
-    type Output = DownloadMessage;
+    type Output = Progress;
 
     fn hash(&self, state: &mut H) {
         use std::hash::Hash;
@@ -27,73 +27,68 @@ where
         self: Box<Self>,
         _input: futures::stream::BoxStream<'static, I>,
     ) -> futures::stream::BoxStream<'static, Self::Output> {
-        use isahc::prelude::*;
-
         Box::pin(futures::stream::unfold(
-            DownloadState::Ready(self.url),
+            State::Ready(self.url),
             |state| async move {
                 match state {
-                    DownloadState::Ready(url) => {
-                        let resp = Request::get(&url)
-                            .metrics(true)
-                            .body(())
-                            .unwrap()
-                            .send_async()
-                            .await
-                            .unwrap();
-                        let metrics = resp.metrics().unwrap().clone();
-                        // If you actually want to download:
-                        /*let file = async_std::fs::File::create("download.bin")
-                        .await
-                        .unwrap();*/
-
-                        async_std::task::spawn(async_std::io::copy(
-                            resp.into_body(),
-                            async_std::io::sink(), //file
-                        ));
+                    State::Ready(url) => {
+                        let response = reqwest::get(&url).await;
 
-                        Some((
-                            DownloadMessage::DownloadStarted,
-                            DownloadState::Downloading(metrics),
-                        ))
+                        match response {
+                            Ok(response) => Some((
+                                Progress::Started,
+                                State::Downloading {
+                                    total: response.content_length().unwrap(),
+                                    downloaded: 0,
+                                    response,
+                                },
+                            )),
+                            Err(_) => None,
+                        }
                     }
-                    DownloadState::Downloading(metrics) => {
-                        async_std::task::sleep(
-                            std::time::Duration::from_millis(100),
-                        )
-                        .await;
+                    State::Downloading {
+                        mut response,
+                        total,
+                        downloaded,
+                    } => match response.chunk().await {
+                        Ok(Some(chunk)) => {
+                            let downloaded = downloaded + chunk.len() as u64;
 
-                        let percentage = metrics.download_progress().0 * 100
-                            / metrics.download_progress().1;
+                            let percentage =
+                                (downloaded as f32 / total as f32) * 100.0;
 
-                        if percentage == 100 {
                             Some((
-                                DownloadMessage::Done,
-                                DownloadState::Finished,
-                            ))
-                        } else {
-                            Some((
-                                DownloadMessage::Downloading(percentage),
-                                DownloadState::Downloading(metrics),
+                                Progress::Advanced(percentage),
+                                State::Downloading {
+                                    response,
+                                    total,
+                                    downloaded,
+                                },
                             ))
                         }
-                    }
-                    DownloadState::Finished => None,
+                        Ok(None) => Some((Progress::Finished, State::Finished)),
+                        Err(_) => None,
+                    },
+                    State::Finished => None,
                 }
             },
         ))
     }
 }
 
-#[derive(Debug)]
-pub enum DownloadMessage {
-    DownloadStarted,
-    Downloading(u64),
-    Done,
+#[derive(Debug, Clone)]
+pub enum Progress {
+    Started,
+    Advanced(f32),
+    Finished,
 }
 
-pub enum DownloadState {
+pub enum State {
     Ready(String),
-    Downloading(isahc::Metrics),
+    Downloading {
+        response: reqwest::Response,
+        total: u64,
+        downloaded: u64,
+    },
     Finished,
 }
diff --git a/examples/download_progress/src/main.rs b/examples/download_progress/src/main.rs
index 936144d5..75e3bee0 100644
--- a/examples/download_progress/src/main.rs
+++ b/examples/download_progress/src/main.rs
@@ -6,60 +6,61 @@ use iced::{
 mod downloader;
 
 pub fn main() {
-    Downloader::run(Settings::default())
-}
-
-#[derive(Debug, Default)]
-struct Downloader {
-    // Whether to start the download or not.
-    enabled: bool,
-    // The current percentage of the download
-    current_progress: u64,
-
-    btn_state: button::State,
+    Example::run(Settings::default())
 }
 
 #[derive(Debug)]
-pub enum Message {
-    DownloadUpdate(downloader::DownloadMessage),
-    Interaction(Interaction),
+enum Example {
+    Idle { button: button::State },
+    Downloading { progress: f32 },
+    Finished { button: button::State },
 }
 
-// For explanation of why we use an Interaction enum see here:
-// https://github.com/hecrj/iced/pull/155#issuecomment-573523405
 #[derive(Debug, Clone)]
-pub enum Interaction {
-    // User pressed the button to start the download
-    StartDownload,
+pub enum Message {
+    DownloadProgressed(downloader::Progress),
+    Download,
 }
 
-impl Application for Downloader {
+impl Application for Example {
     type Executor = executor::Default;
     type Message = Message;
 
-    fn new() -> (Downloader, Command<Message>) {
-        (Downloader::default(), Command::none())
+    fn new() -> (Example, Command<Message>) {
+        (
+            Example::Idle {
+                button: button::State::new(),
+            },
+            Command::none(),
+        )
     }
 
     fn title(&self) -> String {
-        String::from("Download Progress - Iced")
+        String::from("Download progress - Iced")
     }
 
     fn update(&mut self, message: Message) -> Command<Message> {
         match message {
-            Message::Interaction(action) => match action {
-                Interaction::StartDownload => {
-                    self.enabled = true;
+            Message::Download => match self {
+                Example::Idle { .. } | Example::Finished { .. } => {
+                    *self = Example::Downloading { progress: 0.0 };
                 }
+                _ => {}
             },
-            Message::DownloadUpdate(update) => match update {
-                downloader::DownloadMessage::Downloading(percentage) => {
-                    self.current_progress = percentage;
-                }
-                downloader::DownloadMessage::Done => {
-                    self.current_progress = 100;
-                    self.enabled = false;
-                }
+            Message::DownloadProgressed(message) => match self {
+                Example::Downloading { progress } => match message {
+                    downloader::Progress::Started => {
+                        *progress = 0.0;
+                    }
+                    downloader::Progress::Advanced(percentage) => {
+                        *progress = percentage;
+                    }
+                    downloader::Progress::Finished => {
+                        *self = Example::Finished {
+                            button: button::State::new(),
+                        }
+                    }
+                },
                 _ => {}
             },
         };
@@ -68,43 +69,51 @@ impl Application for Downloader {
     }
 
     fn subscription(&self) -> Subscription<Message> {
-        if self.enabled {
-            downloader::file("https://speed.hetzner.de/100MB.bin")
-                .map(Message::DownloadUpdate)
-        } else {
-            Subscription::none()
+        match self {
+            Example::Downloading { .. } => {
+                downloader::file("https://speed.hetzner.de/100MB.bin")
+                    .map(Message::DownloadProgressed)
+            }
+            _ => Subscription::none(),
         }
     }
 
     fn view(&mut self) -> Element<Message> {
-        // Construct widgets
-
-        let toggle_text = match self.enabled {
-            true => "Downloading...",
-            false => "Start the download!",
+        let current_progress = match self {
+            Example::Idle { .. } => 0.0,
+            Example::Downloading { progress } => *progress,
+            Example::Finished { .. } => 100.0,
         };
 
-        let toggle: Element<Interaction> =
-            Button::new(&mut self.btn_state, Text::new(toggle_text))
-                .on_press(Interaction::StartDownload)
-                .into();
-
-        let progress_bar =
-            ProgressBar::new(0.0..=100.0, self.current_progress as f32);
-
-        let progress_text = &match self.enabled {
-            true => format!("Downloading {}%", self.current_progress),
-            false => "Ready to rock!".into(),
+        let progress_bar = ProgressBar::new(0.0..=100.0, current_progress);
+
+        let control: Element<_> = match self {
+            Example::Idle { button } => {
+                Button::new(button, Text::new("Start the download!"))
+                    .on_press(Message::Download)
+                    .into()
+            }
+            Example::Finished { button } => Column::new()
+                .spacing(10)
+                .align_items(Align::Center)
+                .push(Text::new("Download finished!"))
+                .push(
+                    Button::new(button, Text::new("Start again"))
+                        .on_press(Message::Download),
+                )
+                .into(),
+            Example::Downloading { .. } => {
+                Text::new(format!("Downloading... {:.2}%", current_progress))
+                    .into()
+            }
         };
 
-        // Construct layout
         let content = Column::new()
+            .spacing(10)
+            .padding(10)
             .align_items(Align::Center)
-            .spacing(20)
-            .padding(20)
-            .push(Text::new(progress_text))
             .push(progress_bar)
-            .push(toggle.map(Message::Interaction));
+            .push(control);
 
         Container::new(content)
             .width(Length::Fill)