Support async actions in `iced_winit`

7 files changed, 110 insertions, 47 deletions

diff --git a/examples/scroll.rs b/examples/scroll.rs
index 50701879..61ad2a53 100644
--- a/examples/scroll.rs
+++ b/examples/scroll.rs
@@ -1,12 +1,12 @@
 use iced::{
-    button, scrollable, Align, Application, Button, Container, Element, Image,
-    Length, Scrollable, Text,
+    button, scrollable, Align, Application, Button, Command, Container,
+    Element, Image, Length, Scrollable, Text,
 };
 
 pub fn main() {
     env_logger::init();
 
-    Example::default().run()
+    Example::run()
 }
 
 #[derive(Default)]
@@ -25,16 +25,22 @@ pub enum Message {
 impl Application for Example {
     type Message = Message;
 
+    fn new() -> (Example, Command<Message>) {
+        (Example::default(), Command::none())
+    }
+
     fn title(&self) -> String {
         String::from("Scroll - Iced")
     }
 
-    fn update(&mut self, message: Message) {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::AddItem => {
                 self.item_count += 1;
             }
         }
+
+        Command::none()
     }
 
     fn view(&mut self) -> Element<Message> {
diff --git a/examples/todos.rs b/examples/todos.rs
index f921a666..d97a9e08 100644
--- a/examples/todos.rs
+++ b/examples/todos.rs
@@ -1,11 +1,11 @@
 use iced::{
     button, scrollable, text::HorizontalAlignment, text_input, Align,
-    Application, Background, Button, Checkbox, Color, Column, Container,
-    Element, Font, Length, Row, Scrollable, Text, TextInput,
+    Application, Background, Button, Checkbox, Color, Column, Command,
+    Container, Element, Font, Length, Row, Scrollable, Text, TextInput,
 };
 
 pub fn main() {
-    Todos::default().run()
+    Todos::run()
 }
 
 #[derive(Debug, Default)]
@@ -29,11 +29,15 @@ pub enum Message {
 impl Application for Todos {
     type Message = Message;
 
+    fn new() -> (Todos, Command<Message>) {
+        (Todos::default(), Command::none())
+    }
+
     fn title(&self) -> String {
         String::from("Todos - Iced")
     }
 
-    fn update(&mut self, message: Message) {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::InputChanged(value) => {
                 self.input_value = value;
@@ -58,6 +62,8 @@ impl Application for Todos {
         }
 
         dbg!(self);
+
+        Command::none()
     }
 
     fn view(&mut self) -> Element<Message> {
diff --git a/examples/tour.rs b/examples/tour.rs
index 34ad0a34..6d7a080f 100644
--- a/examples/tour.rs
+++ b/examples/tour.rs
@@ -1,13 +1,14 @@
 use iced::{
     button, scrollable, slider, text::HorizontalAlignment, text_input,
-    Application, Background, Button, Checkbox, Color, Column, Container,
-    Element, Image, Length, Radio, Row, Scrollable, Slider, Text, TextInput,
+    Application, Background, Button, Checkbox, Color, Column, Command,
+    Container, Element, Image, Length, Radio, Row, Scrollable, Slider, Text,
+    TextInput,
 };
 
 pub fn main() {
     env_logger::init();
 
-    Tour::new().run()
+    Tour::run()
 }
 
 pub struct Tour {
@@ -18,26 +19,27 @@ pub struct Tour {
     debug: bool,
 }
 
-impl Tour {
-    pub fn new() -> Tour {
-        Tour {
-            steps: Steps::new(),
-            scroll: scrollable::State::new(),
-            back_button: button::State::new(),
-            next_button: button::State::new(),
-            debug: true,
-        }
-    }
-}
-
 impl Application for Tour {
     type Message = Message;
 
+    fn new() -> (Tour, Command<Message>) {
+        (
+            Tour {
+                steps: Steps::new(),
+                scroll: scrollable::State::new(),
+                back_button: button::State::new(),
+                next_button: button::State::new(),
+                debug: true,
+            },
+            Command::none(),
+        )
+    }
+
     fn title(&self) -> String {
         format!("{} - Iced", self.steps.title())
     }
 
-    fn update(&mut self, event: Message) {
+    fn update(&mut self, event: Message) -> Command<Message> {
         match event {
             Message::BackPressed => {
                 self.steps.go_back();
@@ -49,6 +51,8 @@ impl Application for Tour {
                 self.steps.update(step_msg, &mut self.debug);
             }
         }
+
+        Command::none()
     }
 
     fn view(&mut self) -> Element<Message> {
diff --git a/src/lib.rs b/src/lib.rs
index 52b0ff8c..945af421 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,21 +4,23 @@ mod platform;
 
 pub use platform::*;
 
-pub trait Application {
-    type Message: std::fmt::Debug;
+pub trait Application: Sized {
+    type Message: std::fmt::Debug + Send;
+
+    fn new() -> (Self, Command<Self::Message>);
 
     fn title(&self) -> String;
 
-    fn update(&mut self, message: Self::Message);
+    fn update(&mut self, message: Self::Message) -> Command<Self::Message>;
 
     fn view(&mut self) -> Element<Self::Message>;
 
-    fn run(self)
+    fn run()
     where
         Self: 'static + Sized,
     {
         #[cfg(not(target_arch = "wasm32"))]
-        iced_winit::Application::run(Instance(self));
+        <Instance<Self> as iced_winit::Application>::run();
 
         #[cfg(target_arch = "wasm32")]
         iced_web::Application::run(Instance(self));
@@ -35,12 +37,18 @@ where
     type Renderer = Renderer;
     type Message = A::Message;
 
+    fn new() -> (Self, Command<A::Message>) {
+        let (app, command) = A::new();
+
+        (Instance(app), command)
+    }
+
     fn title(&self) -> String {
         self.0.title()
     }
 
-    fn update(&mut self, message: Self::Message) {
-        self.0.update(message);
+    fn update(&mut self, message: Self::Message) -> Command<Self::Message> {
+        self.0.update(message)
     }
 
     fn view(&mut self) -> Element<Self::Message> {
diff --git a/src/winit.rs b/src/winit.rs
index d35a339f..c869a269 100644
--- a/src/winit.rs
+++ b/src/winit.rs
@@ -2,8 +2,8 @@ pub use iced_wgpu::{Primitive, Renderer};
 
 pub use iced_winit::{
     button, scrollable, slider, text, text_input, winit, Align, Background,
-    Checkbox, Color, Font, Image, Length, Radio, Scrollable, Slider, Text,
-    TextInput,
+    Checkbox, Color, Command, Font, Image, Length, Radio, Scrollable, Slider,
+    Text, TextInput,
 };
 
 pub type Element<'a, Message> = iced_winit::Element<'a, Message, Renderer>;
diff --git a/winit/Cargo.toml b/winit/Cargo.toml
index 2831ba2f..2a33255d 100644
--- a/winit/Cargo.toml
+++ b/winit/Cargo.toml
@@ -13,4 +13,5 @@ debug = []
 [dependencies]
 iced_native = { version = "0.1.0-alpha", path = "../native" }
 winit = { version = "0.20.0-alpha3", git = "https://github.com/rust-windowing/winit", rev = "709808eb4e69044705fcb214bcc30556db761405"}
+futures = { version = "0.3", features = ["thread-pool"] }
 log = "0.4"
diff --git a/winit/src/application.rs b/winit/src/application.rs
index 331bafa0..bf41d0c8 100644
--- a/winit/src/application.rs
+++ b/winit/src/application.rs
@@ -2,24 +2,26 @@ use crate::{
     conversion,
     input::{keyboard, mouse},
     renderer::{Target, Windowed},
-    Cache, Container, Debug, Element, Event, Length, MouseCursor,
+    Cache, Command, Container, Debug, Element, Event, Length, MouseCursor,
     UserInterface,
 };
 
-pub trait Application {
+pub trait Application: Sized {
     type Renderer: Windowed;
 
-    type Message: std::fmt::Debug;
+    type Message: std::fmt::Debug + Send;
+
+    fn new() -> (Self, Command<Self::Message>);
 
     fn title(&self) -> String;
 
-    fn update(&mut self, message: Self::Message);
+    fn update(&mut self, message: Self::Message) -> Command<Self::Message>;
 
     fn view(&mut self) -> Element<Self::Message, Self::Renderer>;
 
-    fn run(mut self)
+    fn run()
     where
-        Self: 'static + Sized,
+        Self: 'static,
     {
         use winit::{
             event::{self, WindowEvent},
@@ -28,10 +30,18 @@ pub trait Application {
         };
 
         let mut debug = Debug::new();
-        let mut title = self.title();
 
         debug.startup_started();
-        let event_loop = EventLoop::new();
+        let event_loop = EventLoop::with_user_event();
+        let proxy = event_loop.create_proxy();
+        let mut thread_pool =
+            futures::executor::ThreadPool::new().expect("Create thread pool");
+        let mut external_messages = Vec::new();
+
+        let (mut application, init_command) = Self::new();
+        spawn(init_command, &mut thread_pool, &proxy);
+
+        let mut title = application.title();
 
         // TODO: Ask for window settings and configure this properly
         let window = WindowBuilder::new()
@@ -59,7 +69,7 @@ pub trait Application {
 
         debug.layout_started();
         let user_interface = UserInterface::build(
-            document(&mut self, size, &mut debug),
+            document(&mut application, size, &mut debug),
             Cache::default(),
             &mut renderer,
         );
@@ -85,15 +95,16 @@ pub trait Application {
                 // handled.
                 debug.layout_started();
                 let mut user_interface = UserInterface::build(
-                    document(&mut self, size, &mut debug),
+                    document(&mut application, size, &mut debug),
                     cache.take().unwrap(),
                     &mut renderer,
                 );
                 debug.layout_finished();
 
                 debug.event_processing_started();
-                let messages =
+                let mut messages =
                     user_interface.update(&renderer, events.drain(..));
+                messages.extend(external_messages.drain(..));
                 debug.event_processing_finished();
 
                 if messages.is_empty() {
@@ -113,12 +124,14 @@ pub trait Application {
                         debug.log_message(&message);
 
                         debug.update_started();
-                        self.update(message);
+                        let command = application.update(message);
+
+                        spawn(command, &mut thread_pool, &proxy);
                         debug.update_finished();
                     }
 
                     // Update window title
-                    let new_title = self.title();
+                    let new_title = application.title();
 
                     if title != new_title {
                         window.set_title(&new_title);
@@ -128,7 +141,7 @@ pub trait Application {
 
                     debug.layout_started();
                     let user_interface = UserInterface::build(
-                        document(&mut self, size, &mut debug),
+                        document(&mut application, size, &mut debug),
                         temp_cache,
                         &mut renderer,
                     );
@@ -143,6 +156,9 @@ pub trait Application {
 
                 window.request_redraw();
             }
+            event::Event::UserEvent(message) => {
+                external_messages.push(message);
+            }
             event::Event::RedrawRequested(_) => {
                 debug.render_started();
 
@@ -288,3 +304,25 @@ where
         .height(Length::Units(size.height.round() as u16))
         .into()
 }
+
+fn spawn<Message: Send>(
+    command: Command<Message>,
+    thread_pool: &mut futures::executor::ThreadPool,
+    proxy: &winit::event_loop::EventLoopProxy<Message>,
+) {
+    use futures::FutureExt;
+
+    let futures = command.futures();
+
+    for future in futures {
+        let proxy = proxy.clone();
+
+        let future = future.map(move |message| {
+            proxy
+                .send_event(message)
+                .expect("Send command result to event loop");
+        });
+
+        thread_pool.spawn_ok(future);
+    }
+}