Add support for impl View for Arc/Rc<impl View>

crates/xilem_core/src/view/mod.rs

@@ -3,6 +3,7 @@
 
 mod adapt;
 mod memoize;
+mod rc;
 
 /// Create the `View` trait for a particular xilem context (e.g. html, native, ...).
 ///

crates/xilem_core/src/view/rc.rs

@@ -0,0 +1,44 @@
+// Copyright 2024 the Xilem Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#[macro_export]
+macro_rules! generate_rc_view {
+    (($($rc_ty:tt)*), $viewtrait:ident, $viewmarker:ty, $cx:ty, $changeflags:ty; $($ss:tt)*) => {
+        impl<V> $viewmarker for $( $rc_ty )*<V> {}
+
+        impl<T, A, V: $viewtrait<T, A> $( $ss )*> $viewtrait<T, A> for $( $rc_ty )*<V> {
+            type State = V::State;
+
+            type Element = V::Element;
+
+            fn build(&self, cx: &mut Cx) -> ($crate::Id, Self::State, Self::Element) {
+                V::build(self, cx)
+            }
+
+            fn rebuild(
+                &self,
+                cx: &mut $cx,
+                prev: &Self,
+                id: &mut $crate::Id,
+                state: &mut Self::State,
+                element: &mut Self::Element,
+            ) -> ChangeFlags {
+                if !$( $rc_ty )*::ptr_eq(self, prev) {
+                    V::rebuild(self, cx, prev, id, state, element)
+                } else {
+                    ChangeFlags::empty()
+                }
+            }
+
+            fn message(
+                &self,
+                id_path: &[$crate::Id],
+                state: &mut Self::State,
+                message: Box<dyn std::any::Any>,
+                app_state: &mut T,
+            ) -> $crate::MessageResult<A> {
+                V::message(self, id_path, state, message, app_state)
+            }
+        }
+    };
+}

crates/xilem_web/src/view.rs

@@ -90,6 +90,8 @@ xilem_core::generate_anyview_trait! {AnyView, View, ViewMarker, Cx, ChangeFlags,
 xilem_core::generate_memoize_view! {Memoize, MemoizeState, View, ViewMarker, Cx, ChangeFlags, static_view, memoize;}
 xilem_core::generate_adapt_view! {View, Cx, ChangeFlags;}
 xilem_core::generate_adapt_state_view! {View, Cx, ChangeFlags;}
+xilem_core::generate_rc_view!((std::rc::Rc), View, ViewMarker, Cx, ChangeFlags;);
+xilem_core::generate_rc_view!((std::sync::Arc), View, ViewMarker, Cx, ChangeFlags; + Sync);
 
 // strings -> text nodes
 

src/view/view.rs

@@ -29,6 +29,7 @@ xilem_core::generate_anyview_trait! {AnyView, View, ViewMarker, Cx, ChangeFlags,
 xilem_core::generate_memoize_view! {Memoize, MemoizeState, View, ViewMarker, Cx, ChangeFlags, s, memoize; + Send}
 xilem_core::generate_adapt_view! {View, Cx, ChangeFlags; + Send}
 xilem_core::generate_adapt_state_view! {View, Cx, ChangeFlags; + Send}
+xilem_core::generate_rc_view!((std::sync::Arc), View, ViewMarker, Cx, ChangeFlags; + Sync);
 
 #[derive(Clone)]
 pub struct Cx {