wasm graceful exit

eframe/src/web/backend.rs

@@ -297,15 +297,21 @@ impl AppRunner {
     }
 
     pub fn destroy(&mut self) -> Result<(), JsValue> {
-        tracing::debug!("destroying...");
+        let is_destroyed_already = self.is_destroyed.fetch();
 
-        for x in self.events_to_unsubscribe.drain(..) {
-            x.unsubscribe()?;
-        }
+        if is_destroyed_already {
+            tracing::warn!("App was destroyed already");
+            Ok(())
+        } else {
+            tracing::debug!("Destroying");
+            for x in self.events_to_unsubscribe.drain(..) {
+                x.unsubscribe()?;
+            }
 
-        self.painter.destroy();
-        self.is_destroyed.set_true();
-        Ok(())
+            self.painter.destroy();
+            self.is_destroyed.set_true();
+            Ok(())
+        }
     }
 
     /// Returns how long to wait until the next repaint.

eframe/src/web/events.rs

@@ -1,11 +1,13 @@
 use super::*;
 use std::sync::atomic::{AtomicBool, Ordering};
 
+struct IsDestroyed(pub bool);
+
 pub fn paint_and_schedule(
     runner_ref: &AppRunnerRef,
     panicked: Arc<AtomicBool>,
 ) -> Result<(), JsValue> {
-    fn paint_if_needed(runner_ref: &AppRunnerRef) -> Result<bool, JsValue> {
+    fn paint_if_needed(runner_ref: &AppRunnerRef) -> Result<IsDestroyed, JsValue> {
         let mut runner_lock = runner_ref.lock();
         let is_destroyed = runner_lock.is_destroyed.fetch();
 
@@ -20,7 +22,7 @@ pub fn paint_and_schedule(
             runner_lock.auto_save();
         }
 
-        Ok(is_destroyed)
+        Ok(IsDestroyed(is_destroyed))
     }
 
     fn request_animation_frame(
@@ -38,7 +40,7 @@ pub fn paint_and_schedule(
     // Only paint and schedule if there has been no panic
     if !panicked.load(Ordering::SeqCst) {
         let is_destroyed = paint_if_needed(runner_ref)?;
-        if !is_destroyed {
+        if !is_destroyed.0 {
             request_animation_frame(runner_ref.clone(), panicked)?;
         }
     }