Fix run_on_demand exiting on consequent call

Fixes #3284.

examples/util/fill.rs

@@ -7,17 +7,30 @@
 //! The `softbuffer` crate is used, largely because of its ease of use. `glutin` or `wgpu` could
 //! also be used to fill the window buffer, but they are more complicated to use.
 
-use winit::window::Window;
+#[allow(unused_imports)]
+pub use platform::cleanup_window;
+pub use platform::fill_window;
 
 #[cfg(all(feature = "rwh_05", not(any(target_os = "android", target_os = "ios"))))]
-pub(super) fn fill_window(window: &Window) {
-    use softbuffer::{Context, Surface};
+mod platform {
     use std::cell::RefCell;
     use std::collections::HashMap;
     use std::mem::ManuallyDrop;
     use std::num::NonZeroU32;
+
+    use softbuffer::{Context, Surface};
+    use winit::window::Window;
     use winit::window::WindowId;
 
+    thread_local! {
+        // NOTE: You should never do things like that, create context and drop it before
+        // you drop the event loop. We do this for brevity to not blow up examples. We use
+        // ManuallyDrop to prevent destructors from running.
+        //
+        // A static, thread-local map of graphics contexts to open windows.
+        static GC: ManuallyDrop<RefCell<Option<GraphicsContext>>> = ManuallyDrop::new(RefCell::new(None));
+    }
+
     /// The graphics context used to draw to a window.
     struct GraphicsContext {
         /// The global softbuffer context.
@@ -35,55 +48,69 @@ pub(super) fn fill_window(window: &Window) {
             }
         }
 
-        fn surface(&mut self, w: &Window) -> &mut Surface {
-            self.surfaces.entry(w.id()).or_insert_with(|| {
-                unsafe { Surface::new(&self.context, w) }
+        fn create_surface(&mut self, window: &Window) -> &mut Surface {
+            self.surfaces.entry(window.id()).or_insert_with(|| {
+                unsafe { Surface::new(&self.context, window) }
                     .expect("Failed to create a softbuffer surface")
             })
         }
+
+        fn destroy_surface(&mut self, window: &Window) {
+            self.surfaces.remove(&window.id());
+        }
     }
 
-    thread_local! {
-        // NOTE: You should never do things like that, create context and drop it before
-        // you drop the event loop. We do this for brevity to not blow up examples. We use
-        // ManuallyDrop to prevent destructors from running.
-        //
-        // A static, thread-local map of graphics contexts to open windows.
-        static GC: ManuallyDrop<RefCell<Option<GraphicsContext>>> = ManuallyDrop::new(RefCell::new(None));
+    pub fn fill_window(window: &Window) {
+        GC.with(|gc| {
+            let size = window.inner_size();
+            let (Some(width), Some(height)) =
+                (NonZeroU32::new(size.width), NonZeroU32::new(size.height))
+            else {
+                return;
+            };
+
+            // Either get the last context used or create a new one.
+            let mut gc = gc.borrow_mut();
+            let surface = gc
+                .get_or_insert_with(|| GraphicsContext::new(window))
+                .create_surface(window);
+
+            // Fill a buffer with a solid color.
+            const DARK_GRAY: u32 = 0xFF181818;
+
+            surface
+                .resize(width, height)
+                .expect("Failed to resize the softbuffer surface");
+
+            let mut buffer = surface
+                .buffer_mut()
+                .expect("Failed to get the softbuffer buffer");
+            buffer.fill(DARK_GRAY);
+            buffer
+                .present()
+                .expect("Failed to present the softbuffer buffer");
+        })
     }
 
-    GC.with(|gc| {
-        let size = window.inner_size();
-        let (Some(width), Some(height)) =
-            (NonZeroU32::new(size.width), NonZeroU32::new(size.height))
-        else {
-            return;
-        };
-
-        // Either get the last context used or create a new one.
-        let mut gc = gc.borrow_mut();
-        let surface = gc
-            .get_or_insert_with(|| GraphicsContext::new(window))
-            .surface(window);
-
-        // Fill a buffer with a solid color.
-        const DARK_GRAY: u32 = 0xFF181818;
-
-        surface
-            .resize(width, height)
-            .expect("Failed to resize the softbuffer surface");
-
-        let mut buffer = surface
-            .buffer_mut()
-            .expect("Failed to get the softbuffer buffer");
-        buffer.fill(DARK_GRAY);
-        buffer
-            .present()
-            .expect("Failed to present the softbuffer buffer");
-    })
+    #[allow(dead_code)]
+    pub fn cleanup_window(window: &Window) {
+        GC.with(|gc| {
+            let mut gc = gc.borrow_mut();
+            if let Some(context) = gc.as_mut() {
+                context.destroy_surface(window);
+            }
+        });
+    }
 }
 
 #[cfg(not(all(feature = "rwh_05", not(any(target_os = "android", target_os = "ios")))))]
-pub(super) fn fill_window(_window: &Window) {
-    // No-op on mobile platforms.
+mod platform {
+    pub fn fill_window(_window: &winit::window::Window) {
+        // No-op on mobile platforms.
+    }
+
+    #[allow(dead_code)]
+    pub fn cleanup_window(_window: &winit::window::Window) {
+        // No-op on mobile platforms.
+    }
 }

examples/window_on_demand.rs

@@ -40,6 +40,7 @@ fn main() -> Result<(), impl std::error::Error> {
                         window_id,
                     } if window.id() == window_id => {
                         println!("--------------------------------------------------------- Window {idx} CloseRequested");
+                        fill::cleanup_window(window);
                         app.window = None;
                     }
                     Event::AboutToWait => window.request_redraw(),