async_engine: move toplevel scheduler into crate

async-engine/src/lib.rs

@@ -1,7 +1,8 @@
 mod ae_task;
 mod ae_yield;
+mod run_toplevel;
 
-pub use {ae_task::SpawnedFuture, ae_yield::Yield};
+pub use {ae_task::SpawnedFuture, ae_yield::Yield, run_toplevel::*};
 use {
     crate::ae_task::Runnable,
     jay_time::Time,

async-engine/src/run_toplevel.rs

@@ -0,0 +1,44 @@
+use {
+    crate::{AsyncEngine, SpawnedFuture},
+    jay_utils::queue::AsyncQueue,
+    std::rc::Rc,
+};
+
+pub struct RunToplevelFuture {
+    _future: SpawnedFuture<()>,
+}
+
+pub struct RunToplevel {
+    queue: AsyncQueue<Box<dyn FnOnce()>>,
+}
+
+impl RunToplevel {
+    pub fn install(eng: &Rc<AsyncEngine>) -> (RunToplevelFuture, Rc<RunToplevel>) {
+        let slf = Rc::new(RunToplevel {
+            queue: Default::default(),
+        });
+        let future = eng.spawn("run toplevel", {
+            let slf = slf.clone();
+            async move {
+                loop {
+                    let f = slf.queue.pop().await;
+                    f();
+                }
+            }
+        });
+        let future = RunToplevelFuture { _future: future };
+        (future, slf)
+    }
+
+    pub fn schedule<F: FnOnce() + 'static>(&self, f: F) {
+        self.schedule_dyn(Box::new(f));
+    }
+
+    pub fn clear(&self) {
+        self.queue.clear();
+    }
+
+    fn schedule_dyn(&self, f: Box<dyn FnOnce()>) {
+        self.queue.push(f);
+    }
+}