add ability to disable pipelined rendering

crates/bevy_app/src/app.rs

@@ -161,10 +161,11 @@ impl App {
     /// See [`add_sub_app`](Self::add_sub_app) and [`run_once`](Schedule::run_once) for more details.
     pub fn update(&mut self) {
         #[cfg(feature = "trace")]
-        let _bevy_frame_update_span = info_span!("frame").entered();
+        let _bevy_frame_update_span = info_span!("main_app").entered();
         self.schedule.run(&mut self.world);
         for sub_app in self.sub_apps.values_mut() {
-            (sub_app.extract)(&mut self.world, &mut sub_app.app);
+            sub_app.extract(&mut self.world);
+            sub_app.run();
         }
     }
 

crates/bevy_render/src/lib.rs

@@ -39,6 +39,7 @@ pub mod prelude {
 
 use globals::GlobalsPlugin;
 pub use once_cell;
+use pipelined_rendering::update_rendering;
 use prelude::ComputedVisibility;
 
 use crate::{
@@ -61,8 +62,20 @@ use std::{
 };
 
 /// Contains the default Bevy rendering backend based on wgpu.
-#[derive(Default)]
-pub struct RenderPlugin;
+pub struct RenderPlugin {
+    pub use_pipelined_rendering: bool,
+}
+
+impl Default for RenderPlugin {
+    fn default() -> Self {
+        RenderPlugin {
+            #[cfg(not(target_arch = "wasm32"))]
+            use_pipelined_rendering: true,
+            #[cfg(target_arch = "wasm32")]
+            use_pipelined_rendering: false,
+        }
+    }
+}
 
 /// The labels of the default App rendering stages.
 #[derive(Debug, Hash, PartialEq, Eq, Clone, StageLabel)]
@@ -127,6 +140,10 @@ pub mod main_graph {
 #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, AppLabel)]
 pub struct RenderApp;
 
+/// A Label for the sub app that runs the parts of pipelined rendering that need to run on the main thread.
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, AppLabel)]
+pub struct PipelinedRenderingApp;
+
 impl Plugin for RenderPlugin {
     /// Initializes the renderer, sets up the [`RenderStage`](RenderStage) and creates the rendering sub-app.
     fn build(&self, app: &mut App) {
@@ -220,7 +237,7 @@ impl Plugin for RenderPlugin {
 
             app.add_sub_app(RenderApp, render_app, move |app_world, render_app| {
                 #[cfg(feature = "trace")]
-                let _render_span = bevy_utils::tracing::info_span!("renderer subapp").entered();
+                let _render_span = bevy_utils::tracing::info_span!("extract").entered();
                 {
                     #[cfg(feature = "trace")]
                     let _stage_span =
@@ -327,6 +344,17 @@ impl Plugin for RenderPlugin {
                     render_app.world.clear_entities();
                 }
             });
+
+            if self.use_pipelined_rendering {
+                app.add_sub_app(
+                    PipelinedRenderingApp,
+                    App::new(),
+                    |app_world, _render_app| {
+                        update_rendering(app_world);
+                    },
+                    |_render_world| {},
+                );
+            }
         }
 
         app.add_plugin(ValidParentCheckPlugin::<ComputedVisibility>::default())

crates/bevy_render/src/pipelined_rendering.rs

@@ -1,12 +1,16 @@
 use async_channel::{Receiver, Sender};
 use bevy_app::{App, SubApp};
-use bevy_ecs::{schedule::MainThreadExecutor, system::Resource, world::Mut};
+use bevy_ecs::{
+    schedule::MainThreadExecutor,
+    system::Resource,
+    world::{Mut, World},
+};
 use bevy_tasks::ComputeTaskPool;
 
 #[cfg(feature = "trace")]
 use bevy_utils::tracing::Instrument;
 
-use crate::RenderApp;
+use crate::{PipelinedRenderingApp, RenderApp};
 
 /// Resource to be used for pipelined rendering for sending the render app from the main thread to the rendering thread
 #[derive(Resource)]
@@ -17,7 +21,12 @@ pub struct MainToRenderAppSender(pub Sender<SubApp>);
 pub struct RenderToMainAppReceiver(pub Receiver<SubApp>);
 
 /// sets up the render thread and insert resource into the main app for controlling the render thread
-pub fn setup_pipelined_rendering(app: &mut App) {
+pub fn setup_rendering(app: &mut App) {
+    // skip this if pipelined rendering is not enabled
+    if app.get_sub_app(PipelinedRenderingApp).is_err() {
+        return;
+    }
+
     let (app_to_render_sender, app_to_render_receiver) = async_channel::bounded::<SubApp>(1);
     let (render_to_app_sender, render_to_app_receiver) = async_channel::bounded::<SubApp>(1);
 
@@ -31,55 +40,38 @@ pub fn setup_pipelined_rendering(app: &mut App) {
         loop {
             // TODO: exit loop when app is exited
             let recv_task = app_to_render_receiver.recv();
-            #[cfg(feature = "trace")]
-            let span = bevy_utils::tracing::info_span!("receive render world from main");
-            #[cfg(feature = "trace")]
-            let recv_task = recv_task.instrument(span);
             let mut sub_app = recv_task.await.unwrap();
             sub_app.run();
             render_to_app_sender.send(sub_app).await.unwrap();
         }
     };
     #[cfg(feature = "trace")]
-    let span = bevy_utils::tracing::info_span!("render task");
+    let span = bevy_utils::tracing::info_span!("render app");
     #[cfg(feature = "trace")]
     let render_task = render_task.instrument(span);
     ComputeTaskPool::get().spawn(render_task).detach();
 }
 
-pub fn update_rendering(app: &mut App) {
-    app.update();
-
+pub fn update_rendering(app_world: &mut World) {
     // wait to get the render app back to signal that rendering is finished
-    let mut render_app = app
-        .world
+    let mut render_app = app_world
         .resource_scope(|world, main_thread_executor: Mut<MainThreadExecutor>| {
             ComputeTaskPool::get()
                 .scope(Some(main_thread_executor.0.clone()), |s| {
                     s.spawn(async {
                         let receiver = world.get_resource::<RenderToMainAppReceiver>().unwrap();
                         let recv = receiver.0.recv();
-                        #[cfg(feature = "trace")]
-                        let span = bevy_utils::tracing::info_span!("wait for render");
-                        #[cfg(feature = "trace")]
-                        let recv = recv.instrument(span);
                         recv.await.unwrap()
                     });
                 })
                 .pop()
         })
         .unwrap();
 
-    render_app.extract(&mut app.world);
-
-    {
-        #[cfg(feature = "trace")]
-        let _span = bevy_utils::tracing::info_span!("send world to render").entered();
-        app.world
-            .resource_scope(|_world, sender: Mut<MainToRenderAppSender>| {
-                sender.0.send_blocking(render_app).unwrap();
-            });
-    }
+    render_app.extract(app_world);
 
+    app_world.resource_scope(|_world, sender: Mut<MainToRenderAppSender>| {
+        sender.0.send_blocking(render_app).unwrap();
+    });
     // frame pacing plugin should run here somehow. i.e. after rendering, but before input handling
 }

crates/bevy_winit/src/lib.rs

@@ -4,7 +4,7 @@ mod web_resize;
 mod winit_config;
 mod winit_windows;
 
-use bevy_render::pipelined_rendering::{setup_pipelined_rendering, update_rendering};
+use bevy_render::pipelined_rendering::setup_rendering;
 use converters::convert_cursor_grab_mode;
 pub use winit_config::*;
 pub use winit_windows::*;
@@ -349,7 +349,7 @@ pub fn winit_runner_with(mut app: App) {
 
     let return_from_run = app.world.resource::<WinitSettings>().return_from_run;
 
-    setup_pipelined_rendering(&mut app);
+    setup_rendering(&mut app);
 
     trace!("Entering winit event loop");
 
@@ -592,8 +592,7 @@ pub fn winit_runner_with(mut app: App) {
                 };
                 if update {
                     winit_state.last_update = Instant::now();
-                    update_rendering(&mut app);
-                    // app.update();
+                    app.update();
                 }
             }
             Event::RedrawEventsCleared => {