Fix block_on in iced_wgpu hanging Wasm builds

futures/src/backend/wasm/wasm_bindgen.rs

@@ -1,4 +1,4 @@
-//! A `wasm-bindgein-futures` backend.
+//! A `wasm-bindgen-futures` backend.
 
 /// A `wasm-bindgen-futures` executor.
 #[derive(Debug)]

graphics/src/compositor.rs

@@ -6,6 +6,7 @@ use crate::core::Color;
 use crate::futures::{MaybeSend, MaybeSync};
 
 use raw_window_handle::{HasDisplayHandle, HasWindowHandle};
+use std::future::Future;
 use thiserror::Error;
 
 /// A graphics compositor that can draw to windows.
@@ -23,7 +24,7 @@ pub trait Compositor: Sized {
     fn new<W: Window + Clone>(
         settings: Self::Settings,
         compatible_window: W,
-    ) -> Result<Self, Error>;
+    ) -> impl Future<Output = Result<Self, Error>>;
 
     /// Creates a [`Self::Renderer`] for the [`Compositor`].
     fn create_renderer(&self) -> Self::Renderer;

renderer/src/compositor.rs

@@ -4,6 +4,7 @@ use crate::graphics::{Error, Viewport};
 use crate::{Renderer, Settings};
 
 use std::env;
+use std::future::Future;
 
 pub enum Compositor {
     TinySkia(iced_tiny_skia::window::Compositor),
@@ -25,22 +26,25 @@ impl crate::graphics::Compositor for Compositor {
     fn new<W: Window + Clone>(
         settings: Self::Settings,
         compatible_window: W,
-    ) -> Result<Self, Error> {
+    ) -> impl Future<Output = Result<Self, Error>> {
         let candidates =
             Candidate::list_from_env().unwrap_or(Candidate::default_list());
 
-        let mut error = Error::GraphicsAdapterNotFound;
+        async move {
+            let mut error = Error::GraphicsAdapterNotFound;
 
-        for candidate in candidates {
-            match candidate.build(settings, compatible_window.clone()) {
-                Ok(compositor) => return Ok(compositor),
-                Err(new_error) => {
-                    error = new_error;
+            for candidate in candidates {
+                match candidate.build(settings, compatible_window.clone()).await
+                {
+                    Ok(compositor) => return Ok(compositor),
+                    Err(new_error) => {
+                        error = new_error;
+                    }
                 }
             }
-        }
 
-        Err(error)
+            Err(error)
+        }
     }
 
     fn create_renderer(&self) -> Self::Renderer {
@@ -225,7 +229,7 @@ impl Candidate {
         )
     }
 
-    fn build<W: Window>(
+    async fn build<W: Window>(
         self,
         settings: Settings,
         _compatible_window: W,
@@ -252,7 +256,8 @@ impl Candidate {
                         ..iced_wgpu::Settings::from_env()
                     },
                     _compatible_window,
-                )?;
+                )
+                .await?;
 
                 Ok(Compositor::Wgpu(compositor))
             }

src/application.rs

@@ -205,11 +205,26 @@ pub trait Application: Sized {
             ..crate::renderer::Settings::default()
         };
 
-        Ok(crate::shell::application::run::<
+        let run = crate::shell::application::run::<
             Instance<Self>,
             Self::Executor,
             crate::renderer::Compositor,
-        >(settings.into(), renderer_settings)?)
+        >(settings.into(), renderer_settings);
+
+        #[cfg(target_arch = "wasm32")]
+        {
+            use crate::futures::FutureExt;
+            use iced_futures::backend::wasm::wasm_bindgen::Executor;
+
+            Executor::new()
+                .expect("Create Wasm executor")
+                .spawn(run.map(|_| ()));
+
+            Ok(())
+        }
+
+        #[cfg(not(target_arch = "wasm32"))]
+        Ok(crate::futures::executor::block_on(run)?)
     }
 }
 

tiny_skia/src/window/compositor.rs

@@ -5,6 +5,7 @@ use crate::graphics::{Error, Viewport};
 use crate::{Backend, Primitive, Renderer, Settings};
 
 use std::collections::VecDeque;
+use std::future::{self, Future};
 use std::num::NonZeroU32;
 
 pub struct Compositor {
@@ -31,8 +32,8 @@ impl crate::graphics::Compositor for Compositor {
     fn new<W: compositor::Window>(
         settings: Self::Settings,
         compatible_window: W,
-    ) -> Result<Self, Error> {
-        Ok(new(settings, compatible_window))
+    ) -> impl Future<Output = Result<Self, Error>> {
+        future::ready(Ok(new(settings, compatible_window)))
     }
 
     fn create_renderer(&self) -> Self::Renderer {

wgpu/src/window/compositor.rs

@@ -6,6 +6,8 @@ use crate::graphics::compositor;
 use crate::graphics::{Error, Viewport};
 use crate::{Backend, Primitive, Renderer, Settings};
 
+use std::future::Future;
+
 /// A window graphics backend for iced powered by `wgpu`.
 #[allow(missing_debug_implementations)]
 pub struct Compositor {
@@ -158,17 +160,13 @@ impl Compositor {
 
 /// Creates a [`Compositor`] and its [`Backend`] for the given [`Settings`] and
 /// window.
-pub fn new<W: compositor::Window>(
+pub async fn new<W: compositor::Window>(
     settings: Settings,
     compatible_window: W,
 ) -> Result<Compositor, Error> {
-    let compositor = futures::executor::block_on(Compositor::request(
-        settings,
-        Some(compatible_window),
-    ))
-    .ok_or(Error::GraphicsAdapterNotFound)?;
-
-    Ok(compositor)
+    Compositor::request(settings, Some(compatible_window))
+        .await
+        .ok_or(Error::GraphicsAdapterNotFound)
 }
 
 /// Presents the given primitives with the given [`Compositor`] and [`Backend`].
@@ -234,7 +232,7 @@ impl graphics::Compositor for Compositor {
     fn new<W: compositor::Window>(
         settings: Self::Settings,
         compatible_window: W,
-    ) -> Result<Self, Error> {
+    ) -> impl Future<Output = Result<Self, Error>> {
         new(settings, compatible_window)
     }
 

winit/src/application.rs

@@ -97,7 +97,7 @@ where
 
 /// Runs an [`Application`] with an executor, compositor, and the provided
 /// settings.
-pub fn run<A, E, C>(
+pub async fn run<A, E, C>(
     settings: Settings<A::Flags>,
     compositor_settings: C::Settings,
 ) -> Result<(), Error>
@@ -188,7 +188,7 @@ where
         };
     }
 
-    let compositor = C::new(compositor_settings, window.clone())?;
+    let compositor = C::new(compositor_settings, window.clone()).await?;
     let mut renderer = compositor.create_renderer();
 
     for font in settings.fonts {

winit/src/multi_window.rs

@@ -12,7 +12,9 @@ use crate::core::widget::operation;
 use crate::core::window;
 use crate::core::{Point, Size};
 use crate::futures::futures::channel::mpsc;
-use crate::futures::futures::{task, Future, StreamExt};
+use crate::futures::futures::executor;
+use crate::futures::futures::task;
+use crate::futures::futures::{Future, StreamExt};
 use crate::futures::{Executor, Runtime, Subscription};
 use crate::graphics::{compositor, Compositor};
 use crate::multi_window::window_manager::WindowManager;
@@ -183,7 +185,8 @@ where
         };
     }
 
-    let mut compositor = C::new(compositor_settings, main_window.clone())?;
+    let mut compositor =
+        executor::block_on(C::new(compositor_settings, main_window.clone()))?;
 
     let mut window_manager = WindowManager::new();
     let _ = window_manager.insert(