make signals Not Send

examples/counter-simple/src/main.rs

@@ -1,26 +1,16 @@
-use floem::{
-    reactive::create_signal,
-    views::{button, label, Decorators},
-    IntoView,
-};
+use floem::prelude::*;
 
-fn app_view() -> impl IntoView {
-    // Create a reactive signal with a counter value, defaulting to 0
-    let (counter, mut set_counter) = create_signal(0);
-
-    // Create a vertical layout
-    (
-        // The counter value updates automatically, thanks to reactivity
-        label(move || format!("Value: {counter}")),
-        // Create a horizontal layout
-        (
-            button("Increment").action(move || set_counter += 1),
-            button("Decrement").action(move || set_counter -= 1),
-        ),
-    )
-        .style(|s| s.flex_col())
+fn main() {
+    floem::launch(counter_view);
 }
 
-fn main() {
-    floem::launch(app_view);
+fn counter_view() -> impl IntoView {
+    let mut counter = RwSignal::new(0);
+
+    h_stack((
+        button("Increment").action(move || counter += 1),
+        label(move || format!("Value: {counter}")),
+        button("Decrement").action(move || counter -= 1),
+    ))
+    .style(|s| s.size_full().items_center().justify_center().gap(10))
 }

reactive/src/id.rs

@@ -1,16 +1,23 @@
-use std::sync::atomic::AtomicU64;
+use std::{marker::PhantomData, sync::atomic::AtomicU64};
 
 use crate::{effect::observer_clean_up, runtime::RUNTIME, signal::Signal};
 
+/// Marker type explaining why something can't be sent across threads
+#[allow(dead_code)]
+struct NotThreadSafe(*const ());
+
 /// An internal id which can reference a Signal/Effect/Scope.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Hash)]
-pub struct Id(u64);
+pub struct Id(u64, PhantomData<NotThreadSafe>);
 
 impl Id {
     /// Create a new Id that's next in order
     pub(crate) fn next() -> Id {
         static COUNTER: AtomicU64 = AtomicU64::new(0);
-        Id(COUNTER.fetch_add(1, std::sync::atomic::Ordering::Relaxed))
+        Id(
+            COUNTER.fetch_add(1, std::sync::atomic::Ordering::Relaxed),
+            PhantomData,
+        )
     }
 
     /// Try to get the Signal that links with this Id

src/ext_event.rs

@@ -1,8 +1,8 @@
 use std::{cell::Cell, collections::VecDeque, sync::Arc};
 
 use floem_reactive::{
-    create_effect, untrack, with_scope, ReadSignal, Scope, SignalGet, SignalUpdate, Trigger,
-    WriteSignal,
+    create_effect, create_rw_signal, untrack, with_scope, ReadSignal, RwSignal, Scope, SignalGet,
+    SignalUpdate, SignalWith, WriteSignal,
 };
 use parking_lot::Mutex;
 
@@ -12,10 +12,51 @@ use crate::{
     Application,
 };
 
+#[derive(Debug)]
+/// # SAFETY
+///
+/// **DO NOT USE THIS** trigger except for when using with `create_ext_action` or when you guarentee that
+/// the signal is never used from a different thread than it was created on.
+pub struct SendTrigger {
+    signal: RwSignal<()>,
+}
+
+impl Copy for SendTrigger {}
+
+impl Clone for SendTrigger {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl SendTrigger {
+    pub fn notify(&self) {
+        self.signal.set(());
+    }
+
+    pub fn track(&self) {
+        self.signal.with(|_| {});
+    }
+
+    #[allow(clippy::new_without_default)]
+    pub fn new() -> Self {
+        create_trigger()
+    }
+}
+
+pub fn create_trigger() -> SendTrigger {
+    SendTrigger {
+        signal: create_rw_signal(()),
+    }
+}
+
+unsafe impl Send for SendTrigger {}
+unsafe impl Sync for SendTrigger {}
+
 pub(crate) static EXT_EVENT_HANDLER: ExtEventHandler = ExtEventHandler::new();
 
 pub(crate) struct ExtEventHandler {
-    pub(crate) queue: Mutex<VecDeque<Trigger>>,
+    pub(crate) queue: Mutex<VecDeque<SendTrigger>>,
 }
 
 impl Default for ExtEventHandler {
@@ -31,7 +72,7 @@ impl ExtEventHandler {
         }
     }
 
-    pub fn add_trigger(&self, trigger: Trigger) {
+    pub fn add_trigger(&self, trigger: SendTrigger) {
         {
             // Run this in a short block to prevent any deadlock if running the trigger effects
             // causes another trigger to be registered
@@ -43,7 +84,7 @@ impl ExtEventHandler {
     }
 }
 
-pub fn register_ext_trigger(trigger: Trigger) {
+pub fn register_ext_trigger(trigger: SendTrigger) {
     EXT_EVENT_HANDLER.add_trigger(trigger);
 }
 
@@ -53,7 +94,7 @@ pub fn create_ext_action<T: Send + 'static>(
 ) -> impl FnOnce(T) {
     let view = get_current_view();
     let cx = cx.create_child();
-    let trigger = cx.create_trigger();
+    let trigger = with_scope(cx, SendTrigger::new);
     let data = Arc::new(Mutex::new(None));
 
     {
@@ -87,7 +128,7 @@ pub fn update_signal_from_channel<T: Send + 'static>(
     rx: crossbeam_channel::Receiver<T>,
 ) {
     let cx = Scope::new();
-    let trigger = cx.create_trigger();
+    let trigger = with_scope(cx, SendTrigger::new);
 
     let channel_closed = cx.create_rw_signal(false);
     let data = Arc::new(Mutex::new(VecDeque::new()));
@@ -123,7 +164,7 @@ pub fn create_signal_from_channel<T: Send + 'static>(
     rx: crossbeam_channel::Receiver<T>,
 ) -> ReadSignal<Option<T>> {
     let cx = Scope::new();
-    let trigger = cx.create_trigger();
+    let trigger = with_scope(cx, SendTrigger::new);
 
     let channel_closed = cx.create_rw_signal(false);
     let (read, write) = cx.create_signal(None);
@@ -211,14 +252,14 @@ pub fn create_signal_from_stream<T: 'static>(
     use futures::task::{waker, ArcWake};
 
     let cx = Scope::current().create_child();
-    let trigger = cx.create_trigger();
+    let trigger = with_scope(cx, SendTrigger::new);
     let (read, write) = cx.create_signal(initial_value);
 
     /// Waker that wakes by registering a trigger
     // TODO: since the trigger is just a `u64`, it could theoretically be changed to be a `usize`,
     //       Then the implementation of the std::task::RawWakerVTable could pass the `usize` as the data pointer,
     //       avoiding any allocation/reference counting
-    struct TriggerWake(Trigger);
+    struct TriggerWake(SendTrigger);
     impl ArcWake for TriggerWake {
         fn wake_by_ref(arc_self: &Arc<Self>) {
             EXT_EVENT_HANDLER.add_trigger(arc_self.0);