From 7792b29aa40785a37f49d51f0241e6329c91a185 Mon Sep 17 00:00:00 2001
From: TheRawMeatball <therawmeatball@gmail.com>
Date: Wed, 30 Jun 2021 00:43:56 +0300
Subject: [PATCH] Force main thread for prepare_windows system (#11)

Force main thread for prepare_windows system
---
 pipelined/bevy_render2/src/view/window.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/pipelined/bevy_render2/src/view/window.rs b/pipelined/bevy_render2/src/view/window.rs
index 760b8e1a69..3173da919c 100644
--- a/pipelined/bevy_render2/src/view/window.rs
+++ b/pipelined/bevy_render2/src/view/window.rs
@@ -11,6 +11,10 @@ use bevy_window::{RawWindowHandleWrapper, WindowId, Windows};
 use std::ops::{Deref, DerefMut};
 use wgpu::TextureFormat;
 
+// Token to ensure a system runs on the main thread.
+#[derive(Default)]
+pub struct NonSendMarker;
+
 pub struct WindowRenderPlugin;
 
 impl Plugin for WindowRenderPlugin {
@@ -18,6 +22,7 @@ impl Plugin for WindowRenderPlugin {
         let render_app = app.sub_app_mut(0);
         render_app
             .init_resource::<WindowSurfaces>()
+            .init_resource::<NonSendMarker>()
             .add_system_to_stage(RenderStage::Extract, extract_windows.system())
             .add_system_to_stage(RenderStage::Prepare, prepare_windows.system());
     }
@@ -77,6 +82,9 @@ pub struct WindowSurfaces {
 }
 
 pub fn prepare_windows(
+    // By accessing a NonSend resource, we tell the scheduler to put this system on the main thread,
+    // which is necessary for some OS s
+    _marker: NonSend<NonSendMarker>,
     mut windows: ResMut<ExtractedWindows>,
     mut window_surfaces: ResMut<WindowSurfaces>,
     render_device: Res<RenderDevice>,
@@ -88,6 +96,7 @@ pub fn prepare_windows(
             .surfaces
             .entry(window.id)
             .or_insert_with(|| unsafe {
+                // NOTE: On some OSes this MUST be called from the main thread.
                 render_instance.create_surface(&window.handle.get_handle())
             });