Don't store JsValue in ListenerProduct

crates/kobold/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "kobold"
-version = "0.7.0"
+version = "0.8.0"
 authors = ["Maciej Hirsz <[email protected]>"]
 edition = "2021"
 license = "MPL-2.0"
@@ -19,7 +19,7 @@ stateful = []
 wasm-bindgen = "0.2.84"
 wasm-bindgen-futures = "0.4.34"
 itoa = "1.0.6"
-kobold_macros = { version = "0.7.0", path = "../kobold_macros" }
+kobold_macros = { version = "0.8.0", path = "../kobold_macros" }
 console_error_panic_hook = "0.1.7"
 
 [dependencies.web-sys]

crates/kobold/src/event.rs

@@ -6,6 +6,7 @@
 
 use std::marker::PhantomData;
 use std::ops::Deref;
+use std::ptr::NonNull;
 
 use wasm_bindgen::closure::Closure;
 use wasm_bindgen::prelude::wasm_bindgen;
@@ -87,43 +88,57 @@ where
     E: EventCast,
     Self: Sized + 'static,
 {
-    fn build(self) -> ListenerProduct<Self>;
+    type Product: ListenerHandle;
 
-    fn update(self, p: &mut ListenerProduct<Self>);
+    fn build(self) -> Self::Product;
+
+    fn update(self, p: &mut Self::Product);
 }
 
 impl<E, F> Listener<E> for F
 where
     F: FnMut(E) + 'static,
     E: EventCast,
 {
-    fn build(self) -> ListenerProduct<Self> {
-        let raw = Box::leak(Box::new(self));
-
-        let js = Closure::wrap(unsafe {
-            Box::from_raw(raw as *mut dyn FnMut(E) as *mut dyn FnMut(web_sys::Event))
-        })
-        .into_js_value();
+    type Product = ListenerProduct<Self, E>;
 
-        // `into_js_value` will _forget_ the previous Box, so we can safely reconstruct it
-        let boxed = unsafe { Box::from_raw(raw) };
+    fn build(self) -> ListenerProduct<Self, E> {
+        ListenerProduct {
+            raw: Box::leak(Box::new(self)).into(),
+            _event: PhantomData,
+        }
+    }
 
-        ListenerProduct { js, boxed }
+    fn update(self, p: &mut ListenerProduct<Self, E>) {
+        unsafe { *p.raw.as_ptr() = self };
     }
+}
+
+pub struct ListenerProduct<F, E> {
+    raw: NonNull<F>,
+    _event: PhantomData<E>,
+}
 
-    fn update(self, p: &mut ListenerProduct<Self>) {
-        *p.boxed = self;
+impl<F, E> Drop for ListenerProduct<F, E> {
+    fn drop(&mut self) {
+        unsafe { drop(Box::from_raw(self.raw.as_ptr())) }
     }
 }
 
-pub struct ListenerProduct<F> {
-    js: JsValue,
-    boxed: Box<F>,
+pub trait ListenerHandle {
+    fn js(&self) -> JsValue;
 }
 
-impl<F> ListenerProduct<F> {
-    pub fn js(&self) -> &JsValue {
-        &self.js
+impl<F, E> ListenerHandle for ListenerProduct<F, E>
+where
+    F: FnMut(E) + 'static,
+    E: EventCast,
+{
+    fn js(&self) -> JsValue {
+        Closure::wrap(unsafe {
+            Box::from_raw(self.raw.as_ptr() as *mut dyn FnMut(E) as *mut dyn FnMut(web_sys::Event))
+        })
+        .into_js_value()
     }
 }
 

crates/kobold/src/stateful/hook.rs

@@ -3,6 +3,7 @@
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 use std::future::Future;
+use std::marker::PhantomData;
 use std::mem::ManuallyDrop;
 use std::ops::Deref;
 use std::rc::{Rc, Weak};
@@ -102,7 +103,7 @@ impl<S> Hook<S> {
     {
         let inner = &self.inner as *const Inner<S>;
 
-        move |e| {
+        let bound = move |e| {
             // ⚠️ Safety:
             // ==========
             //
@@ -115,6 +116,11 @@ impl<S> Hook<S> {
             if callback(state, e).should_render() {
                 inner.update();
             }
+        };
+
+        Bound {
+            bound,
+            _unbound: PhantomData::<F>,
         }
     }
 
@@ -157,6 +163,33 @@ impl<S> Hook<S> {
     }
 }
 
+struct Bound<B, U> {
+    bound: B,
+    _unbound: PhantomData<U>,
+}
+
+impl<B, U, E> Listener<E> for Bound<B, U>
+where
+    B: Listener<E>,
+    E: EventCast,
+    Self: 'static,
+{
+    type Product = B::Product;
+
+    fn build(self) -> Self::Product {
+        self.bound.build()
+    }
+
+    fn update(self, p: &mut Self::Product) {
+        // No need to update zero-sized closures.
+        //
+        // This is a const branch that should be optimized away.
+        if std::mem::size_of::<U>() != 0 {
+            self.bound.update(p);
+        }
+    }
+}
+
 impl<S> Deref for Hook<S> {
     type Target = S;
 

crates/kobold_macros/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "kobold_macros"
-version = "0.7.0"
+version = "0.8.0"
 authors = ["Maciej Hirsz <[email protected]>"]
 edition = "2021"
 license = "MPL-2.0"

crates/kobold_macros/src/gen/element.rs

@@ -143,7 +143,7 @@ impl IntoGenerator for HtmlElement {
                             writeln!(el, "{var}.addEventListener(\"{}\",{value});", &name[2..])
                         });
 
-                        el.args.push(JsArgument::new(value))
+                        el.args.push(JsArgument::with_abi(value, InlineAbi::Event))
                     }
                     AttributeType::Provided(attr) => {
                         el.hoisted = true;
@@ -206,27 +206,31 @@ impl IntoGenerator for HtmlElement {
 pub enum InlineAbi {
     Bool,
     Str,
+    Event,
 }
 
 impl InlineAbi {
     pub fn abi(self) -> &'static str {
         match self {
             InlineAbi::Bool => "bool",
             InlineAbi::Str => "&str",
+            InlineAbi::Event => "wasm_bindgen::JsValue",
         }
     }
 
-    pub fn method(self) -> &'static str {
+    pub fn method(self) -> Option<&'static str> {
         match self {
-            InlineAbi::Bool => ".into()",
-            InlineAbi::Str => ".as_ref()",
+            InlineAbi::Bool => Some(".into()"),
+            InlineAbi::Str => Some(".as_ref()"),
+            InlineAbi::Event => None,
         }
     }
 
     pub fn bound(self) -> &'static str {
         match self {
             InlineAbi::Bool => "+ Into<bool> + Copy",
             InlineAbi::Str => "+ AsRef<str>",
+            InlineAbi::Event => "",
         }
     }
 }

crates/kobold_macros/src/gen/transient.rs

@@ -140,19 +140,11 @@ impl Tokenize for Transient {
 
             match field.kind {
                 FieldKind::StaticView => (),
-                FieldKind::View | FieldKind::Attribute { .. } => {
+                _ => {
                     let _ = write!(product_generics, "{typ},");
                     let _ = write!(product_generics_binds, "{typ}::Product,");
                     field.declare(&mut product_declare);
                 }
-                FieldKind::Event { .. } => {
-                    let _ = write!(product_generics, "{typ},");
-                    let _ = write!(
-                        product_generics_binds,
-                        "::kobold::event::ListenerProduct<{typ}>,"
-                    );
-                    field.declare(&mut product_declare);
-                }
             }
         }
 
@@ -170,7 +162,7 @@ impl Tokenize for Transient {
                 .map(|a| {
                     let mut temp = ArrayString::<24>::new();
                     let name = a.name;
-                    let _ = match a.abi.map(InlineAbi::method) {
+                    let _ = match a.abi.and_then(|abi| abi.method()) {
                         Some(method) => write!(temp, "self.{name}{method}"),
                         None => write!(temp, "{name}.js()"),
                     };
@@ -189,7 +181,8 @@ impl Tokenize for Transient {
         block((
             (
                 "\
-                use ::kobold::dom::{Mountable as _};\
+                use ::kobold::dom::Mountable as _;\
+                use ::kobold::event::ListenerHandle as _;\
                 use ::kobold::reexport::wasm_bindgen;\
                 ",
                 self.js,

crates/kobold_qr/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "kobold_qr"
-version = "0.7.0"
+version = "0.8.0"
 authors = ["Maciej Hirsz <[email protected]>"]
 edition = "2021"
 license = "MPL-2.0"
@@ -10,7 +10,7 @@ description = "QR code component for Kobold"
 
 [dependencies]
 fast_qr = "0.8.5"
-kobold = { version = "0.7.0", path = "../kobold" }
+kobold = { version = "0.8.0", path = "../kobold" }
 wasm-bindgen = "0.2.84"
 
 [dependencies.web-sys]