Implement async Compositor::request in iced_wgpu

wgpu/src/window/compositor.rs

@@ -1,4 +1,4 @@
-use crate::{Renderer, Settings};
+use crate::{Backend, Renderer, Settings};
 
 use iced_graphics::Viewport;
 use iced_native::{futures, mouse};
@@ -7,19 +7,19 @@ use raw_window_handle::HasRawWindowHandle;
 /// A window graphics backend for iced powered by `wgpu`.
 #[derive(Debug)]
 pub struct Compositor {
+    settings: Settings,
     device: wgpu::Device,
     queue: wgpu::Queue,
-    format: wgpu::TextureFormat,
 }
 
-impl iced_graphics::window::Compositor for Compositor {
+impl Compositor {
-    type Settings = Settings;
+    /// Requests a new [`Compositor`] with the given [`Settings`].
-    type Renderer = Renderer;
+    ///
-    type Surface = wgpu::Surface;
+    /// Returns `None` if no compatible graphics adapter could be found.
-    type SwapChain = wgpu::SwapChain;
+    ///
-
+    /// [`Compositor`]: struct.Compositor.html
-    fn new(settings: Self::Settings) -> (Self, Renderer) {
+    /// [`Settings`]: struct.Settings.html
-        let (mut device, queue) = futures::executor::block_on(async {
+    pub async fn request(settings: Settings) -> Option<Self> {
         let adapter = wgpu::Adapter::request(
             &wgpu::RequestAdapterOptions {
                 power_preference: if settings.antialiasing.is_none() {
@@ -31,30 +31,46 @@ impl iced_graphics::window::Compositor for Compositor {
             },
             wgpu::BackendBit::PRIMARY,
         )
-            .await
+        .await?;
-            .expect("Request adapter");
 
-            adapter
+        let (device, queue) = adapter
             .request_device(&wgpu::DeviceDescriptor {
                 extensions: wgpu::Extensions {
                     anisotropic_filtering: false,
                 },
                 limits: wgpu::Limits { max_bind_groups: 2 },
             })
-                .await
+            .await;
-        });
 
-        let renderer =
+        Some(Compositor {
-            Renderer::new(crate::Backend::new(&mut device, settings));
+            settings,
-
-        (
-            Self {
             device,
             queue,
-                format: settings.format,
+        })
-            },
+    }
-            renderer,
+
-        )
+    /// Creates a new rendering [`Backend`] for this [`Compositor`].
+    ///
+    /// [`Compositor`]: struct.Compositor.html
+    /// [`Backend`]: struct.Backend.html
+    pub fn create_backend(&self) -> Backend {
+        Backend::new(&self.device, self.settings)
+    }
+}
+
+impl iced_graphics::window::Compositor for Compositor {
+    type Settings = Settings;
+    type Renderer = Renderer;
+    type Surface = wgpu::Surface;
+    type SwapChain = wgpu::SwapChain;
+
+    fn new(settings: Self::Settings) -> (Self, Renderer) {
+        let compositor = futures::executor::block_on(Self::request(settings))
+            .expect("Could not find a suitable graphics adapter");
+
+        let backend = compositor.create_backend();
+
+        (compositor, Renderer::new(backend))
     }
 
     fn create_surface<W: HasRawWindowHandle>(
@@ -74,7 +90,7 @@ impl iced_graphics::window::Compositor for Compositor {
             surface,
             &wgpu::SwapChainDescriptor {
                 usage: wgpu::TextureUsage::OUTPUT_ATTACHMENT,
-                format: self.format,
+                format: self.settings.format,
                 width,
                 height,
                 present_mode: wgpu::PresentMode::Mailbox,