Fix high-signal widget and Wayland warnings

Avoid recursive operation traversal, execute visible list updates instead of leaving a lazy iterator unused, remove unreachable cfg-gated surface creation code, and handle subsurface buffer attachment failures.

widget/src/container.rs

@@ -601,7 +601,7 @@ pub fn visible_bounds(id: Id) -> Task<Option<Rectangle>> {
             operate: &mut dyn FnMut(&mut dyn Operation<Option<Rectangle>>),
         ) {
             self.depth += 1;
-            self.traverse(operate);
+            operate(self);
             self.depth -= 1;
         }
 

winit/src/platform_specific/mod.rs

@@ -153,9 +153,12 @@ impl PlatformSpecific {
     ) -> Option<Box<dyn HasWindowHandle + Send + Sync + 'static>> {
         #[cfg(all(feature = "cctk", target_os = "linux"))]
         {
-            return self.wayland.create_surface();
+            self.wayland.create_surface()
+        }
+        #[cfg(not(all(feature = "cctk", target_os = "linux")))]
+        {
+            None
         }
-        None
     }
 
     pub(crate) fn update_surface_shm(

winit/src/platform_specific/wayland/subsurface_widget.rs

@@ -409,7 +409,10 @@ impl SubsurfaceState {
             .unwrap();
         canvas[0..width as usize * height as usize * 4].copy_from_slice(data);
         surface.damage_buffer(0, 0, width as i32, height as i32);
-        buffer.attach_to(&surface);
+        if let Err(err) = buffer.attach_to(&surface) {
+            log::warn!("failed to attach shm buffer to subsurface: {err}");
+            return;
+        }
         surface.offset(offset.x as i32, offset.y as i32);
         wp_viewport.set_destination(
             (width as f64 / scale) as i32,