From 07376d11e8b33639df3e002f2631dff27c289802 Mon Sep 17 00:00:00 2001
From: Frizi <frizi09@gmail.com>
Date: Thu, 3 Jun 2021 13:02:56 +0200
Subject: [PATCH] Handle winit exception in web to avoid breaking async
 executor

---
 wgpu/examples/framework.rs | 23 ++++++++++++++++++++++-
 wgpu/src/backend/direct.rs |  2 +-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/wgpu/examples/framework.rs b/wgpu/examples/framework.rs
index 6f8e875af8..493e622643 100644
--- a/wgpu/examples/framework.rs
+++ b/wgpu/examples/framework.rs
@@ -357,10 +357,31 @@ pub fn run<E: Example>(title: &str) {
 
 #[cfg(target_arch = "wasm32")]
 pub fn run<E: Example>(title: &str) {
+    use wasm_bindgen::{prelude::*, JsCast};
+
     let title = title.to_owned();
     wasm_bindgen_futures::spawn_local(async move {
         let setup = setup::<E>(&title).await;
-        start::<E>(setup);
+        let start_closure = Closure::once_into_js(move || start::<E>(setup));
+
+        // make sure to handle JS exceptions thrown inside start.
+        // Otherwise wasm_bindgen_futures Queue would break and never handle any tasks again.
+        // This is required, because winit uses JS exception for control flow to escape from `run`.
+        if let Err(error) = call_catch(&start_closure) {
+            let is_control_flow_exception = error.dyn_ref::<js_sys::Error>().map_or(false, |e| {
+                e.message().includes("Using exceptions for control flow", 0)
+            });
+
+            if !is_control_flow_exception {
+                web_sys::console::error_1(&error);
+            }
+        }
+
+        #[wasm_bindgen]
+        extern "C" {
+            #[wasm_bindgen(catch, js_namespace = Function, js_name = "prototype.call.call")]
+            fn call_catch(this: &JsValue) -> Result<(), JsValue>;
+        }
     });
 }
 
diff --git a/wgpu/src/backend/direct.rs b/wgpu/src/backend/direct.rs
index c50a599c37..878bcbb874 100644
--- a/wgpu/src/backend/direct.rs
+++ b/wgpu/src/backend/direct.rs
@@ -1940,7 +1940,7 @@ impl fmt::Debug for ErrorSinkRaw {
 }
 
 fn default_error_handler(err: crate::Error) {
-    eprintln!("wgpu error: {}\n", err);
+    log::error!("wgpu error: {}\n", err);
 
     panic!("Handling wgpu errors as fatal by default");
 }