Add `Application::Executor` associated type

29 files changed, 192 insertions, 69 deletions

diff --git a/Cargo.toml b/Cargo.toml
index fbe3b9f2..87f3000e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,6 +41,7 @@ iced_web = { version = "0.1.0", path = "web" }
 [dev-dependencies]
 iced_native = { version = "0.1", path = "./native" }
 iced_wgpu = { version = "0.1", path = "./wgpu" }
+iced_futures = { version = "0.1.0-alpha", path = "./futures", features = ["async-std"] }
 env_logger = "0.7"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
diff --git a/examples/events.rs b/examples/events.rs
index 74542171..0c9dca05 100644
--- a/examples/events.rs
+++ b/examples/events.rs
@@ -1,6 +1,6 @@
 use iced::{
-    Align, Application, Checkbox, Column, Command, Container, Element, Length,
-    Settings, Subscription, Text,
+    executor, Align, Application, Checkbox, Column, Command, Container,
+    Element, Length, Settings, Subscription, Text,
 };
 
 pub fn main() {
@@ -20,6 +20,7 @@ enum Message {
 }
 
 impl Application for Events {
+    type Executor = executor::Default;
     type Message = Message;
 
     fn new() -> (Events, Command<Message>) {
diff --git a/examples/pokedex.rs b/examples/pokedex.rs
index 7326f94f..505dbf19 100644
--- a/examples/pokedex.rs
+++ b/examples/pokedex.rs
@@ -27,6 +27,7 @@ enum Message {
 }
 
 impl Application for Pokedex {
+    type Executor = iced_futures::executor::AsyncStd;
     type Message = Message;
 
     fn new() -> (Pokedex, Command<Message>) {
diff --git a/examples/stopwatch.rs b/examples/stopwatch.rs
index 2bc85c4d..6e357039 100644
--- a/examples/stopwatch.rs
+++ b/examples/stopwatch.rs
@@ -28,6 +28,7 @@ enum Message {
 }
 
 impl Application for Stopwatch {
+    type Executor = iced_futures::executor::AsyncStd;
     type Message = Message;
 
     fn new() -> (Stopwatch, Command<Message>) {
diff --git a/examples/todos.rs b/examples/todos.rs
index 4166f75a..06595a1e 100644
--- a/examples/todos.rs
+++ b/examples/todos.rs
@@ -38,6 +38,7 @@ enum Message {
 }
 
 impl Application for Todos {
+    type Executor = iced_futures::executor::AsyncStd;
     type Message = Message;
 
     fn new() -> (Todos, Command<Message>) {
diff --git a/futures/Cargo.toml b/futures/Cargo.toml
index 5b303e01..13c2d6b7 100644
--- a/futures/Cargo.toml
+++ b/futures/Cargo.toml
@@ -23,3 +23,7 @@ version = "0.3"
 version = "0.2"
 optional = true
 features = ["rt-core"]
+
+[dependencies.async-std]
+version = "1.0"
+optional = true
diff --git a/futures/src/executor.rs b/futures/src/executor.rs
new file mode 100644
index 00000000..144a41f8
--- /dev/null
+++ b/futures/src/executor.rs
@@ -0,0 +1,36 @@
+//! Choose your preferred executor to power a runtime.
+mod null;
+
+#[cfg(feature = "thread-pool")]
+mod thread_pool;
+
+#[cfg(feature = "thread-pool")]
+pub use thread_pool::ThreadPool;
+
+#[cfg(feature = "tokio")]
+mod tokio;
+
+#[cfg(feature = "async-std")]
+mod async_std;
+
+pub use null::Null;
+
+#[cfg(feature = "tokio")]
+pub use self::tokio::Tokio;
+
+#[cfg(feature = "async-std")]
+pub use self::async_std::AsyncStd;
+
+use futures::Future;
+
+pub trait Executor: Sized {
+    fn new() -> Result<Self, futures::io::Error>
+    where
+        Self: Sized;
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static);
+
+    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        f()
+    }
+}
diff --git a/futures/src/executor/async_std.rs b/futures/src/executor/async_std.rs
new file mode 100644
index 00000000..b056b23d
--- /dev/null
+++ b/futures/src/executor/async_std.rs
@@ -0,0 +1,15 @@
+use crate::Executor;
+
+use futures::Future;
+
+pub struct AsyncStd;
+
+impl Executor for AsyncStd {
+    fn new() -> Result<Self, futures::io::Error> {
+        Ok(Self)
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        let _ = async_std::task::spawn(future);
+    }
+}
diff --git a/futures/src/executor/null.rs b/futures/src/executor/null.rs
new file mode 100644
index 00000000..722073bb
--- /dev/null
+++ b/futures/src/executor/null.rs
@@ -0,0 +1,13 @@
+use crate::Executor;
+
+use futures::Future;
+
+pub struct Null;
+
+impl Executor for Null {
+    fn new() -> Result<Self, futures::io::Error> {
+        Ok(Self)
+    }
+
+    fn spawn(&self, _future: impl Future<Output = ()> + Send + 'static) {}
+}
diff --git a/futures/src/executor/thread_pool.rs b/futures/src/executor/thread_pool.rs
new file mode 100644
index 00000000..6393d0d5
--- /dev/null
+++ b/futures/src/executor/thread_pool.rs
@@ -0,0 +1,15 @@
+use crate::Executor;
+
+use futures::Future;
+
+pub type ThreadPool = futures::executor::ThreadPool;
+
+impl Executor for futures::executor::ThreadPool {
+    fn new() -> Result<Self, futures::io::Error> {
+        futures::executor::ThreadPool::new()
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        self.spawn_ok(future);
+    }
+}
diff --git a/futures/src/executor/tokio.rs b/futures/src/executor/tokio.rs
new file mode 100644
index 00000000..aafa7e7b
--- /dev/null
+++ b/futures/src/executor/tokio.rs
@@ -0,0 +1,19 @@
+use crate::Executor;
+
+use futures::Future;
+
+pub type Tokio = tokio::runtime::Runtime;
+
+impl Executor for Tokio {
+    fn new() -> Result<Self, futures::io::Error> {
+        tokio::runtime::Runtime::new()
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        let _ = tokio::runtime::Runtime::spawn(self, future);
+    }
+
+    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        tokio::runtime::Runtime::enter(self, f)
+    }
+}
diff --git a/futures/src/lib.rs b/futures/src/lib.rs
index f6bcf85a..832a50f6 100644
--- a/futures/src/lib.rs
+++ b/futures/src/lib.rs
@@ -1,8 +1,12 @@
+pub use futures;
+
 mod command;
+mod runtime;
 
-pub mod runtime;
+pub mod executor;
 pub mod subscription;
 
 pub use command::Command;
+pub use executor::Executor;
 pub use runtime::Runtime;
 pub use subscription::Subscription;
diff --git a/futures/src/runtime.rs b/futures/src/runtime.rs
index 37905c61..a508c46e 100644
--- a/futures/src/runtime.rs
+++ b/futures/src/runtime.rs
@@ -1,9 +1,5 @@
-//! Run commands and subscriptions.
-mod executor;
-
-pub use executor::Executor;
-
-use crate::{subscription, Command, Subscription};
+//! Run commands and keep track of subscriptions.
+use crate::{subscription, Command, Executor, Subscription};
 
 use futures::Sink;
 use std::marker::PhantomData;
diff --git a/futures/src/runtime/executor.rs b/futures/src/runtime/executor.rs
deleted file mode 100644
index eec5e231..00000000
--- a/futures/src/runtime/executor.rs
+++ /dev/null
@@ -1,27 +0,0 @@
-use futures::Future;
-
-pub trait Executor {
-    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static);
-
-    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
-        f()
-    }
-}
-
-#[cfg(feature = "thread-pool")]
-impl Executor for futures::executor::ThreadPool {
-    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
-        self.spawn_ok(future);
-    }
-}
-
-#[cfg(feature = "tokio")]
-impl Executor for tokio::runtime::Runtime {
-    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
-        let _ = tokio::runtime::Runtime::spawn(self, future);
-    }
-
-    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
-        tokio::runtime::Runtime::enter(self, f)
-    }
-}
diff --git a/native/Cargo.toml b/native/Cargo.toml
index 57a869e2..6276535e 100644
--- a/native/Cargo.toml
+++ b/native/Cargo.toml
@@ -11,7 +11,6 @@ repository = "https://github.com/hecrj/iced"
 twox-hash = "1.5"
 raw-window-handle = "0.3"
 unicode-segmentation = "1.6"
-futures = "0.3"
 
 [dependencies.iced_core]
 version = "0.1.0"
@@ -20,3 +19,4 @@ path = "../core"
 [dependencies.iced_futures]
 version = "0.1.0-alpha"
 path = "../futures"
+features = ["thread-pool"]
diff --git a/native/src/lib.rs b/native/src/lib.rs
index 7730c6a3..b5856c00 100644
--- a/native/src/lib.rs
+++ b/native/src/lib.rs
@@ -42,7 +42,6 @@
 pub mod input;
 pub mod layout;
 pub mod renderer;
-pub mod runtime;
 pub mod subscription;
 pub mod widget;
 pub mod window;
@@ -52,6 +51,7 @@ mod element;
 mod event;
 mod hasher;
 mod mouse_cursor;
+mod runtime;
 mod size;
 mod user_interface;
 
@@ -59,7 +59,10 @@ pub use iced_core::{
     Align, Background, Color, Font, HorizontalAlignment, Length, Point,
     Rectangle, Vector, VerticalAlignment,
 };
-pub use iced_futures::Command;
+pub use iced_futures::{executor, futures, Command};
+
+#[doc(no_inline)]
+pub use executor::Executor;
 
 pub use clipboard::Clipboard;
 pub use element::Element;
diff --git a/native/src/runtime.rs b/native/src/runtime.rs
index 2b3abbf1..9fa031f4 100644
--- a/native/src/runtime.rs
+++ b/native/src/runtime.rs
@@ -10,5 +10,3 @@ use crate::{Event, Hasher};
 /// [`Subscription`]: ../struct.Subscription.html
 pub type Runtime<Executor, Receiver, Message> =
     iced_futures::Runtime<Hasher, Event, Executor, Receiver, Message>;
-
-pub use iced_futures::runtime::Executor;
diff --git a/native/src/subscription.rs b/native/src/subscription.rs
index 43f1758a..0d002c6c 100644
--- a/native/src/subscription.rs
+++ b/native/src/subscription.rs
@@ -1,6 +1,6 @@
 //! Listen to external events in your application.
 use crate::{Event, Hasher};
-use futures::stream::BoxStream;
+use iced_futures::futures::stream::BoxStream;
 
 /// A request to listen to external events.
 ///
diff --git a/native/src/subscription/events.rs b/native/src/subscription/events.rs
index 6ff2c0fb..7d33166e 100644
--- a/native/src/subscription/events.rs
+++ b/native/src/subscription/events.rs
@@ -2,6 +2,7 @@ use crate::{
     subscription::{EventStream, Recipe},
     Event, Hasher,
 };
+use iced_futures::futures::stream::BoxStream;
 
 pub struct Events;
 
@@ -17,7 +18,7 @@ impl Recipe<Hasher, Event> for Events {
     fn stream(
         self: Box<Self>,
         event_stream: EventStream,
-    ) -> futures::stream::BoxStream<'static, Self::Output> {
+    ) -> BoxStream<'static, Self::Output> {
         event_stream
     }
 }
diff --git a/src/application.rs b/src/application.rs
index b940cc17..3a526f1b 100644
--- a/src/application.rs
+++ b/src/application.rs
@@ -1,4 +1,4 @@
-use crate::{window, Command, Element, Settings, Subscription};
+use crate::{window, Command, Element, Executor, Settings, Subscription};
 
 /// An interactive cross-platform application.
 ///
@@ -19,7 +19,7 @@ use crate::{window, Command, Element, Settings, Subscription};
 /// before](index.html#overview). We just need to fill in the gaps:
 ///
 /// ```no_run
-/// use iced::{button, Application, Button, Column, Command, Element, Settings, Text};
+/// use iced::{button, executor, Application, Button, Column, Command, Element, Settings, Text};
 ///
 /// pub fn main() {
 ///     Counter::run(Settings::default())
@@ -39,6 +39,7 @@ use crate::{window, Command, Element, Settings, Subscription};
 /// }
 ///
 /// impl Application for Counter {
+///     type Executor = executor::Null;
 ///     type Message = Message;
 ///
 ///     fn new() -> (Self, Command<Message>) {
@@ -80,6 +81,14 @@ use crate::{window, Command, Element, Settings, Subscription};
 /// }
 /// ```
 pub trait Application: Sized {
+    /// The [`Executor`] that will run commands and subscriptions.
+    ///
+    /// The [`executor::Default`] can be a good starting point!
+    ///
+    /// [`Executor`]: trait.Executor.html
+    /// [`executor::Default`]: executor/struct.Default.html
+    type Executor: Executor;
+
     /// The type of __messages__ your [`Application`] will produce.
     ///
     /// [`Application`]: trait.Application.html
@@ -185,6 +194,7 @@ where
     A: Application,
 {
     type Renderer = iced_wgpu::Renderer;
+    type Executor = A::Executor;
     type Message = A::Message;
 
     fn new() -> (Self, Command<A::Message>) {
diff --git a/src/lib.rs b/src/lib.rs
index 759dea2f..18dfc098 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -180,18 +180,26 @@
 #![deny(unsafe_code)]
 #![deny(rust_2018_idioms)]
 mod application;
-#[cfg(target_arch = "wasm32")]
-#[path = "web.rs"]
-mod platform;
-#[cfg(not(target_arch = "wasm32"))]
-#[path = "native.rs"]
-mod platform;
 mod sandbox;
 
+#[cfg(not(target_arch = "wasm32"))]
+mod native;
+
+#[cfg(not(target_arch = "wasm32"))]
+pub use native::*;
+
+#[cfg(target_arch = "wasm32")]
+mod web;
+
+#[cfg(target_arch = "wasm32")]
+pub use web::*;
+
 pub mod settings;
 pub mod window;
 
+#[doc(no_inline)]
+pub use executor::Executor;
+
 pub use application::Application;
-pub use platform::*;
 pub use sandbox::Sandbox;
 pub use settings::Settings;
diff --git a/src/native.rs b/src/native.rs
index 35441a3e..86ccffab 100644
--- a/src/native.rs
+++ b/src/native.rs
@@ -3,6 +3,8 @@ pub use iced_winit::{
     Space, Subscription, Vector, VerticalAlignment,
 };
 
+pub mod executor;
+
 pub mod widget {
     //! Display information and interactive controls in your application.
     //!
diff --git a/src/native/executor.rs b/src/native/executor.rs
new file mode 100644
index 00000000..68a1d280
--- /dev/null
+++ b/src/native/executor.rs
@@ -0,0 +1,23 @@
+//! Choose your preferred executor to power your application.
+pub use iced_winit::{executor::Null, Executor};
+use iced_winit::{executor::ThreadPool, futures};
+
+/// The default cross-platform executor.
+///
+/// - On native platforms, it will use a `ThreadPool`.
+/// - On the Web, it will use `wasm-bindgen-futures::spawn_local`.
+#[derive(Debug)]
+pub struct Default(ThreadPool);
+
+impl Executor for Default {
+    fn new() -> Result<Self, futures::io::Error> {
+        Ok(Default(ThreadPool::new()?))
+    }
+
+    fn spawn(
+        &self,
+        future: impl futures::Future<Output = ()> + Send + 'static,
+    ) {
+        self.0.spawn(future);
+    }
+}
diff --git a/src/sandbox.rs b/src/sandbox.rs
index dda4c3f5..2c0332ff 100644
--- a/src/sandbox.rs
+++ b/src/sandbox.rs
@@ -1,4 +1,4 @@
-use crate::{Application, Command, Element, Settings, Subscription};
+use crate::{executor, Application, Command, Element, Settings, Subscription};
 
 /// A sandboxed [`Application`].
 ///
@@ -133,6 +133,7 @@ impl<T> Application for T
 where
     T: Sandbox,
 {
+    type Executor = executor::Null;
     type Message = T::Message;
 
     fn new() -> (Self, Command<T::Message>) {
diff --git a/web/Cargo.toml b/web/Cargo.toml
index ea092575..46953863 100644
--- a/web/Cargo.toml
+++ b/web/Cargo.toml
@@ -18,7 +18,6 @@ maintenance = { status = "actively-developed" }
 dodrio = "0.1.0"
 wasm-bindgen = "0.2.51"
 wasm-bindgen-futures = "0.4"
-futures = "0.3"
 
 [dependencies.iced_core]
 version = "0.1.0"
diff --git a/web/src/lib.rs b/web/src/lib.rs
index b183c390..c44b99b5 100644
--- a/web/src/lib.rs
+++ b/web/src/lib.rs
@@ -75,7 +75,7 @@ pub use iced_core::{
     Align, Background, Color, Font, HorizontalAlignment, Length,
     VerticalAlignment,
 };
-pub use iced_futures::Command;
+pub use iced_futures::{futures, Command};
 pub use style::Style;
 pub use subscription::Subscription;
 pub use widget::*;
diff --git a/winit/Cargo.toml b/winit/Cargo.toml
index ba6d5229..cef41e9c 100644
--- a/winit/Cargo.toml
+++ b/winit/Cargo.toml
@@ -16,17 +16,11 @@ debug = []
 [dependencies]
 winit = { version = "0.20.0-alpha3", git = "https://github.com/hecrj/winit", rev = "709808eb4e69044705fcb214bcc30556db761405"}
 log = "0.4"
-futures = "0.3"
 
 [dependencies.iced_native]
 version = "0.1.0-alpha"
 path = "../native"
 
-[dependencies.iced_futures]
-version = "0.1.0-alpha"
-path = "../futures"
-features = ["thread-pool"]
-
 [dependencies.window_clipboard]
 git = "https://github.com/hecrj/window_clipboard"
 rev = "22c6dd6c04cd05d528029b50a30c56417cd4bebf"
diff --git a/winit/src/application.rs b/winit/src/application.rs
index 076ac092..4b21a930 100644
--- a/winit/src/application.rs
+++ b/winit/src/application.rs
@@ -1,10 +1,9 @@
 use crate::{
     conversion,
     input::{keyboard, mouse},
-    window, Cache, Clipboard, Command, Debug, Element, Event, Mode,
-    MouseCursor, Proxy, Settings, Size, Subscription, UserInterface,
+    window, Cache, Clipboard, Command, Debug, Element, Event, Executor, Mode,
+    MouseCursor, Proxy, Runtime, Settings, Size, Subscription, UserInterface,
 };
-use iced_native::Runtime;
 
 /// An interactive, native cross-platform application.
 ///
@@ -20,6 +19,11 @@ pub trait Application: Sized {
     /// [`Application`]: trait.Application.html
     type Renderer: window::Renderer;
 
+    /// The [`Executor`] that will run commands and subscriptions.
+    ///
+    /// [`Executor`]: trait.Executor.html
+    type Executor: Executor;
+
     /// The type of __messages__ your [`Application`] will produce.
     ///
     /// [`Application`]: trait.Application.html
@@ -110,13 +114,13 @@ pub trait Application: Sized {
 
         debug.startup_started();
         let event_loop = EventLoop::with_user_event();
+        let mut external_messages = Vec::new();
+
         let mut runtime = {
-            let thread_pool = futures::executor::ThreadPool::new()
-                .expect("Create thread pool");
+            let executor = Self::Executor::new().expect("Create executor");
 
-            Runtime::new(thread_pool, Proxy::new(event_loop.create_proxy()))
+            Runtime::new(executor, Proxy::new(event_loop.create_proxy()))
         };
-        let mut external_messages = Vec::new();
 
         let (mut application, init_command) = Self::new();
         runtime.spawn(init_command);
diff --git a/winit/src/proxy.rs b/winit/src/proxy.rs
index 7e8dee98..cff9df33 100644
--- a/winit/src/proxy.rs
+++ b/winit/src/proxy.rs
@@ -1,4 +1,4 @@
-use futures::{
+use iced_native::futures::{
     task::{Context, Poll},
     Sink,
 };