diff --git a/nested/src/core/channel.rs b/nested/src/core/channel.rs
index 453f17c..6f86a0e 100644
--- a/nested/src/core/channel.rs
+++ b/nested/src/core/channel.rs
@@ -86,7 +86,7 @@ pub struct ChannelReceiver<Data: ChannelData>(Arc<Mutex<ChannelState<Data>>>);
 impl<Data: ChannelData> ChannelSender<Data>
 where Data::IntoIter: Send + Sync {
     pub fn send(&self, msg: Data::Item) {
-        let mut state =  self.0.lock().unwrap();
+        let mut state = self.0.lock().unwrap();
 
         if state.send_buf.is_none() {
             state.send_buf = Some(Data::default());
@@ -103,7 +103,7 @@ where Data::IntoIter: Send + Sync {
 use crate::core::View;
 impl<V: View + ?Sized, Data: ChannelData<Item = V::Msg>> Observer<V> for ChannelSender<Data>
 where V::Msg: Clone, Data::IntoIter: Send + Sync {
-    fn notify(&self, msg: &V::Msg) {
+    fn notify(&mut self, msg: &V::Msg) {
         self.send(msg.clone());
     }
 }
@@ -131,6 +131,15 @@ impl<Data: ChannelData> ChannelReceiver<Data> {
     pub async fn recv(&self) -> Option<Data> {
         ChannelRead(self.0.clone()).await
     }
+
+    pub fn try_recv(&self) -> Option<Data> {
+        let mut state = self.0.lock().unwrap();
+        if let Some(buf) = state.send_buf.take() {
+            Some(buf)
+        } else {
+            None
+        }        
+    }
 }
 
 struct ChannelRead<Data: ChannelData>(Arc<Mutex<ChannelState<Data>>>);
diff --git a/nested/src/core/context.rs b/nested/src/core/context.rs
index bc02cf3..5131927 100644
--- a/nested/src/core/context.rs
+++ b/nested/src/core/context.rs
@@ -76,8 +76,8 @@ pub struct Object {
 }
 
 impl Object {
-    pub fn get_port<V: View + ?Sized + 'static>(&self) -> Option<OuterViewPort<V>> {
-        Some(self.repr.read().unwrap().port.clone()?.downcast::<V>().unwrap())
+    pub fn get_port<V: View + ?Sized + 'static>(&self) -> Option<OuterViewPort<V>> where V::Msg: Clone {
+        Some(self.repr.read().unwrap().port.clone()?.downcast::<V>().ok().unwrap())
     }
 
     pub fn downcast(&self, dst_type: TypeTerm) -> Option<Object> {
@@ -201,6 +201,8 @@ impl Object {
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
+pub struct TypeLadder(Vec<TypeTerm>);
+
 #[derive(Clone, Copy, Hash, PartialEq, Eq)]
 pub enum MorphismMode {
     /// Isomorphism
@@ -310,7 +312,8 @@ impl Context {
         &self,
         name: &str,
         type_ladder: impl Iterator<Item = &'a str>
-    ) -> Option<OuterViewPort<V>> {
+    ) -> Option<OuterViewPort<V>>
+    where V::Msg: Clone {
         self.get_obj(&name.into())?
             .downcast_ladder(
                 type_ladder.map(|tn| self.type_dict.type_term_from_str(tn).unwrap())
@@ -367,7 +370,8 @@ impl Context {
         &mut self,
         name: &str,
         type_ladder: impl Iterator<Item = &'a str>
-    ) -> Option<OuterViewPort<V>> {
+    ) -> Option<OuterViewPort<V>>
+    where V::Msg: Clone {
         if let Some(p) = self.get_obj_port(name, type_ladder) {
             Some(p)
         } else {
diff --git a/nested/src/core/observer.rs b/nested/src/core/observer.rs
index dfa0afc..38eb8f9 100644
--- a/nested/src/core/observer.rs
+++ b/nested/src/core/observer.rs
@@ -1,5 +1,10 @@
 use {
-    crate::core::View,
+    crate::{
+        core::{
+            View,
+            channel::{channel, ChannelSender, ChannelReceiver}
+        }
+    },
     std::{
         sync::{Arc, Weak}
     },
@@ -13,7 +18,7 @@ use {
                     \*/
 pub trait Observer<V: View + ?Sized> : Send + Sync {
     fn reset(&mut self, _view: Option<Arc<V>>) {}
-    fn notify(&self, msg: &V::Msg);
+    fn notify(&mut self, msg: &V::Msg);
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
@@ -23,19 +28,19 @@ impl<V: View + ?Sized, O: Observer<V>> Observer<V> for Arc<RwLock<O>> {
         self.write().unwrap().reset(view);
     }
 
-    fn notify(&self, msg: &V::Msg) {
-        self.read().unwrap().notify(&msg);
+    fn notify(&mut self, msg: &V::Msg) {
+        self.write().unwrap().notify(msg);
     }
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
 pub trait ObserverExt<V: View + ?Sized> : Observer<V> {    
-    fn notify_each(&self, it: impl IntoIterator<Item = V::Msg>);
+    fn notify_each(&mut self, it: impl IntoIterator<Item = V::Msg>);
 }
 
 impl<V: View + ?Sized, T: Observer<V>> ObserverExt<V> for T {
-    fn notify_each(&self, it: impl IntoIterator<Item = V::Msg>) {
+    fn notify_each(&mut self, it: impl IntoIterator<Item = V::Msg>) {
         for msg in it {
             self.notify(&msg);
         }
@@ -47,14 +52,19 @@ impl<V: View + ?Sized, T: Observer<V>> ObserverExt<V> for T {
                  Broadcast
 <<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
                     \*/
-
-pub struct ObserverBroadcast<V: View + ?Sized> {
+pub struct ObserverBroadcast<V: View + ?Sized>
+where V::Msg : Send + Sync {
+    rx: ChannelReceiver<Vec<V::Msg>>,
+    tx: ChannelSender<Vec<V::Msg>>,
     observers: Vec<Weak<RwLock<dyn Observer<V>>>>
 }
 
-impl<V: View + ?Sized> ObserverBroadcast<V> {
+impl<V: View + ?Sized> ObserverBroadcast<V>
+where V::Msg : Clone + Send + Sync {
     pub fn new() -> Self {
+        let (tx, rx) = channel::<Vec<V::Msg>>();
         ObserverBroadcast {
+            rx, tx,
             observers: Vec::new()
         }
     }
@@ -71,19 +81,28 @@ impl<V: View + ?Sized> ObserverBroadcast<V> {
     fn iter(&self) -> impl Iterator<Item = Arc<RwLock<dyn Observer<V>>>> + '_ {
         self.observers.iter().filter_map(|o| o.upgrade())
     }
+
+    pub fn update(&self) {
+        if let Some(msg_vec) = self.rx.try_recv() {
+            for msg in msg_vec {
+                for o in self.iter() {
+                    o.write().unwrap().notify(&msg);
+                }
+            }
+        }
+    }
 }
 
-impl<V: View + ?Sized> Observer<V> for ObserverBroadcast<V> {
+impl<V: View + ?Sized> Observer<V> for ObserverBroadcast<V>
+where V::Msg: Clone {
     fn reset(&mut self, view: Option<Arc<V>>) {
         for o in self.iter() {
             o.write().unwrap().reset(view.clone());
         }
     }
 
-    fn notify(&self, msg: &V::Msg) {
-        for o in self.iter() {
-            o.read().unwrap().notify(&msg);
-        }
+    fn notify(&mut self, msg: &V::Msg) {
+        self.tx.send(msg.clone());
     }
 }
 
@@ -110,7 +129,7 @@ where V: View + ?Sized,
 impl<V, F> Observer<V> for NotifyFnObserver<V, F>
 where V: View + ?Sized,
       F: Fn(&V::Msg) + Send + Sync {
-    fn notify(&self, msg: &V::Msg) {
+    fn notify(&mut self, msg: &V::Msg) {
         (self.f)(msg);
     }
 }
@@ -138,7 +157,7 @@ where V: View + ?Sized,
 impl<V, F> Observer<V> for ResetFnObserver<V, F>
 where V: View + ?Sized,
       F: Fn(Option<Arc<V>>) + Send + Sync {
-    fn notify(&self, _msg: &V::Msg) {}
+    fn notify(&mut self, _msg: &V::Msg) {}
     fn reset(&mut self, view: Option<Arc<V>>) {
         (self.f)(view);
     }
diff --git a/nested/src/core/port.rs b/nested/src/core/port.rs
index 9e871aa..e36db56 100644
--- a/nested/src/core/port.rs
+++ b/nested/src/core/port.rs
@@ -11,6 +11,11 @@ use {
     }
 };
 
+
+pub trait UpdateTask : Send + Sync {
+    fn update(&self);
+}
+
                     /*\
 <<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
                  View Port
@@ -18,14 +23,17 @@ use {
                     \*/
 pub struct ViewPort<V: View + ?Sized> {
     view: Arc<RwLock<Option<Arc<V>>>>,
-    cast: Arc<RwLock<ObserverBroadcast<V>>>
+    cast: Arc<RwLock<ObserverBroadcast<V>>>,
+    pub update_hooks: Arc<RwLock<Vec<Arc<dyn UpdateTask>>>>
 }
 
-impl<V: View + ?Sized> ViewPort<V> {
+impl<V: View + ?Sized> ViewPort<V>
+where V::Msg: Clone {
     pub fn new() -> Self {
         ViewPort {
             view: Arc::new(RwLock::new(None)),
-            cast: Arc::new(RwLock::new(ObserverBroadcast::new()))
+            cast: Arc::new(RwLock::new(ObserverBroadcast::new())),
+            update_hooks: Arc::new(RwLock::new(Vec::new()))
         }
     }
 
@@ -45,40 +53,86 @@ impl<V: View + ?Sized> ViewPort<V> {
         observer.write().unwrap().reset(self.view.read().unwrap().clone());
     }
 
+    pub fn add_update_hook(&self, hook_cast: Arc<dyn UpdateTask>) {
+        self.update_hooks.write().unwrap().push(hook_cast);
+    }
+
     pub fn inner(&self) -> InnerViewPort<V> {
-        InnerViewPort(ViewPort{ view: self.view.clone(), cast: self.cast.clone() })
+        InnerViewPort(
+            ViewPort{
+                view: self.view.clone(),
+                cast: self.cast.clone(),
+                update_hooks: self.update_hooks.clone()
+            }
+        )
     }
 
     pub fn outer(&self) -> OuterViewPort<V> {
-        OuterViewPort(ViewPort{ view: self.view.clone(), cast: self.cast.clone() })
+        OuterViewPort(
+            ViewPort{
+                view: self.view.clone(),
+                cast: self.cast.clone(),
+                update_hooks: self.update_hooks.clone()
+            }
+        )
     }
 
     pub fn into_inner(self) -> InnerViewPort<V> {
-        InnerViewPort(ViewPort{ view: self.view, cast: self.cast })
+        InnerViewPort(
+            ViewPort{
+                view: self.view,
+                cast: self.cast,
+                update_hooks: self.update_hooks
+            }
+        )
     }
 
     pub fn into_outer(self) -> OuterViewPort<V> {
-        OuterViewPort(ViewPort{ view: self.view, cast: self.cast })
+        OuterViewPort(
+            ViewPort{
+                view: self.view,
+                cast: self.cast,
+                update_hooks: self.update_hooks
+            }
+        )
     }
 }
 
-impl<V: View + ?Sized> Clone for ViewPort<V> {
+impl<V: View + ?Sized> UpdateTask for ViewPort<V> where V::Msg: Clone + Send + Sync{
+    fn update(&self) {
+        let mut v = {
+            let t = self.update_hooks.read().unwrap();
+            t.iter().cloned().collect::<Vec<_>>()
+        };
+
+        for hook in v {
+            hook.update();
+        }
+
+        self.cast.read().unwrap().update();
+    }
+}
+
+
+impl<V: View + ?Sized> Clone for ViewPort<V>
+where V::Msg: Clone {
     fn clone(&self) -> Self {
         ViewPort {
             view: self.view.clone(),
-            cast: self.cast.clone()
+            cast: self.cast.clone(),
+            update_hooks: self.update_hooks.clone()
         }
     }
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-pub struct InnerViewPort<V: View + ?Sized>(ViewPort<V>);
-pub struct OuterViewPort<V: View + ?Sized>(ViewPort<V>);
+pub struct InnerViewPort<V: View + ?Sized>(pub ViewPort<V>) where V::Msg: Clone;
+pub struct OuterViewPort<V: View + ?Sized>(pub ViewPort<V>) where V::Msg: Clone;
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-impl<V: View + ?Sized> InnerViewPort<V> {
+impl<V: View + ?Sized> InnerViewPort<V> where V::Msg: Clone {
     pub fn get_broadcast(&self) -> Arc<RwLock<ObserverBroadcast<V>>> {
         self.0.cast.clone()
     }
@@ -93,11 +147,12 @@ impl<V: View + ?Sized> InnerViewPort<V> {
     }
 
     pub fn notify(&self, msg: &V::Msg) {
-        self.0.cast.read().unwrap().notify(msg);
+        self.0.cast.write().unwrap().notify(msg);
     }
 }
 
-impl<V: View + ?Sized> Clone for InnerViewPort<V> {
+impl<V: View + ?Sized> Clone for InnerViewPort<V>
+where V::Msg: Clone {
     fn clone(&self) -> Self {
         InnerViewPort(self.0.clone())
     }
@@ -105,7 +160,8 @@ impl<V: View + ?Sized> Clone for InnerViewPort<V> {
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-impl<V: View + ?Sized + 'static> OuterViewPort<V> {
+impl<V: View + ?Sized + 'static> OuterViewPort<V>
+where V::Msg: Clone {
     pub fn get_view(&self) -> Option<Arc<V>> {
         self.0.view.read().unwrap().clone()
     }
@@ -132,7 +188,8 @@ impl<V: View + ?Sized + 'static> OuterViewPort<V> {
     }
 }
 
-impl<V: View + ?Sized> Clone for OuterViewPort<V> {
+impl<V: View + ?Sized> Clone for OuterViewPort<V>
+where V::Msg: Clone {
     fn clone(&self) -> Self {
         OuterViewPort(self.0.clone())
     }
@@ -160,19 +217,21 @@ where V::Msg: Clone {
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct AnyViewPort {
     view: Arc<dyn Any + Send + Sync + 'static>,
-    cast: Arc<dyn Any + Send + Sync + 'static>
+    cast: Arc<dyn Any + Send + Sync + 'static>,
+    update_hooks: Arc<RwLock<Vec<Arc<dyn UpdateTask>>>>
 }
 
 impl AnyViewPort {
     pub fn downcast<V: View + ?Sized + 'static>(self) -> Result<ViewPort<V>, AnyViewPort> {
         match (
             self.view.clone().downcast::<RwLock<Option<Arc<V>>>>(),
-            self.cast.clone().downcast::<RwLock<ObserverBroadcast<V>>>()
+            self.cast.clone().downcast::<RwLock<ObserverBroadcast<V>>>(),
+            self.update_hooks.clone()
         ) {
-            (Ok(view), Ok(cast)) => Ok(ViewPort{view, cast}),
+            (Ok(view), Ok(cast), update_hooks) => Ok(ViewPort{view, cast, update_hooks}),
             _ => Err(self)
         }
     }
@@ -182,45 +241,50 @@ impl<V: View + ?Sized + 'static> From<ViewPort<V>> for AnyViewPort {
     fn from(port: ViewPort<V>) -> Self {
         AnyViewPort {
             view: port.view as Arc<dyn Any + Send + Sync + 'static>,
-            cast: port.cast as Arc<dyn Any + Send + Sync + 'static>
+            cast: port.cast as Arc<dyn Any + Send + Sync + 'static>,
+            update_hooks: port.update_hooks
         }
     }
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct AnyOuterViewPort(AnyViewPort);
 
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct AnyInnerViewPort(AnyViewPort);
 
 impl AnyOuterViewPort {
-    pub fn downcast<V: View + ?Sized + 'static>(self) -> Result<OuterViewPort<V>, AnyViewPort> {
+    pub fn downcast<V: View + ?Sized + 'static>(self) -> Result<OuterViewPort<V>, AnyViewPort> where V::Msg: Clone {
         Ok(OuterViewPort(self.0.downcast::<V>()?))
     }
 }
 
-impl<V: View + ?Sized + 'static> From<OuterViewPort<V>> for AnyOuterViewPort {
+impl<V: View + ?Sized + 'static> From<OuterViewPort<V>> for AnyOuterViewPort
+where V::Msg: Clone {
     fn from(port: OuterViewPort<V>) -> Self {
         AnyOuterViewPort(AnyViewPort{
             view: port.0.view as Arc<dyn Any + Send + Sync + 'static>,
-            cast: port.0.cast as Arc<dyn Any + Send + Sync + 'static>
+            cast: port.0.cast as Arc<dyn Any + Send + Sync + 'static>,
+            update_hooks: port.0.update_hooks
         })
     }
 }
 
 impl AnyInnerViewPort {
-    pub fn downcast<V: View + ?Sized + 'static>(self) -> Result<InnerViewPort<V>, AnyViewPort> {
+    pub fn downcast<V: View + ?Sized + 'static>(self) -> Result<InnerViewPort<V>, AnyViewPort> where V::Msg: Clone {
         Ok(InnerViewPort(self.0.downcast::<V>()?))
     }
 }
 
-impl<V: View + ?Sized + 'static> From<InnerViewPort<V>> for AnyInnerViewPort {
+impl<V: View + ?Sized + 'static> From<InnerViewPort<V>> for AnyInnerViewPort
+where V::Msg: Clone {
     fn from(port: InnerViewPort<V>) -> Self {
         AnyInnerViewPort(AnyViewPort{
             view: port.0.view as Arc<dyn Any + Send + Sync + 'static>,
-            cast: port.0.cast as Arc<dyn Any + Send + Sync + 'static>
+            cast: port.0.cast as Arc<dyn Any + Send + Sync + 'static>,
+            update_hooks: port.0.update_hooks
         })
     }
 }
diff --git a/nested/src/core/view.rs b/nested/src/core/view.rs
index 1b5a33c..b3da6e6 100644
--- a/nested/src/core/view.rs
+++ b/nested/src/core/view.rs
@@ -6,7 +6,7 @@
                     \*/
 pub trait View : Send + Sync {
     /// Notification message for the observers
-    type Msg;
+    type Msg : Send + Sync;
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
diff --git a/nested/src/grid/offset.rs b/nested/src/grid/offset.rs
index 1b406ad..77d9ab1 100644
--- a/nested/src/grid/offset.rs
+++ b/nested/src/grid/offset.rs
@@ -77,7 +77,7 @@ impl<V: GridView + ?Sized> Observer<V> for GridOffset<V> {
         if let Some(area) = new_area { self.cast.notify_each(area); }
     }
 
-    fn notify(&self, msg: &Point2<i16>) {
+    fn notify(&mut self, msg: &Point2<i16>) {
         self.cast.notify(&(msg + self.offset));
     }
 }
diff --git a/nested/src/index/map_item.rs b/nested/src/index/map_item.rs
index 6cee0ee..f12f2c6 100644
--- a/nested/src/index/map_item.rs
+++ b/nested/src/index/map_item.rs
@@ -18,7 +18,10 @@ pub use {
     }
 };
 
-impl<Key: 'static, Item: 'static> OuterViewPort<dyn IndexView<Key, Item = Item>> {
+impl<Key, Item> OuterViewPort<dyn IndexView<Key, Item = Item>>
+where Key: Clone + Send + Sync + 'static,
+      Item: Send + Sync + 'static
+{
     pub fn map_item<
         DstItem: 'static,
         F: Fn(&Key, &Item) -> DstItem + Send + Sync + 'static
@@ -27,6 +30,8 @@ impl<Key: 'static, Item: 'static> OuterViewPort<dyn IndexView<Key, Item = Item>>
         f: F
     ) -> OuterViewPort<dyn IndexView<Key, Item = DstItem>> {
         let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
         let map = MapIndexItem::new(port.inner(), f);
         self.add_observer(map.clone());
         port.into_outer()
@@ -34,7 +39,8 @@ impl<Key: 'static, Item: 'static> OuterViewPort<dyn IndexView<Key, Item = Item>>
 }
 
 pub struct MapIndexItem<Key, DstItem, SrcView, F>
-where SrcView: IndexView<Key> + ?Sized,
+where Key: Clone + Send + Sync,
+      SrcView: IndexView<Key> + ?Sized,
       F: Fn(&Key, &SrcView::Item) -> DstItem + Send + Sync
 {
     src_view: Option<Arc<SrcView>>,
@@ -43,7 +49,7 @@ where SrcView: IndexView<Key> + ?Sized,
 }
 
 impl<Key, DstItem, SrcView, F> MapIndexItem<Key, DstItem, SrcView, F>
-where Key: 'static,
+where Key: Clone + Send + Sync + 'static,
       DstItem: 'static,
       SrcView: IndexView<Key> + ?Sized + 'static,
       F: Fn(&Key, &SrcView::Item) -> DstItem + Send + Sync + 'static
@@ -66,14 +72,16 @@ where Key: 'static,
 }
 
 impl<Key, DstItem, SrcView, F> View for MapIndexItem<Key, DstItem, SrcView, F>
-where SrcView: IndexView<Key> + ?Sized,
+where Key: Clone + Send + Sync,
+      SrcView: IndexView<Key> + ?Sized,
       F: Fn(&Key, &SrcView::Item) -> DstItem + Send + Sync
 {
     type Msg = Key;
 }
 
 impl<Key, DstItem, SrcView, F> IndexView<Key> for MapIndexItem<Key, DstItem, SrcView, F>
-where SrcView: IndexView<Key> + ?Sized,
+where Key: Clone + Send + Sync,
+      SrcView: IndexView<Key> + ?Sized,
       F: Fn(&Key, &SrcView::Item) -> DstItem + Send + Sync
 {
     type Item = DstItem;
@@ -88,7 +96,8 @@ where SrcView: IndexView<Key> + ?Sized,
 }
 
 impl<Key, DstItem, SrcView, F> Observer<SrcView> for MapIndexItem<Key, DstItem, SrcView, F>
-where SrcView: IndexView<Key> + ?Sized,
+where Key: Clone + Send + Sync,
+      SrcView: IndexView<Key> + ?Sized,
       F: Fn(&Key, &SrcView::Item) -> DstItem + Send + Sync
 {
     fn reset(&mut self, view: Option<Arc<SrcView>>) {
@@ -100,7 +109,7 @@ where SrcView: IndexView<Key> + ?Sized,
         if let Some(area) = new_area { self.cast.notify_each(area); }
     }
 
-    fn notify(&self, msg: &Key) {
+    fn notify(&mut self, msg: &Key) {
         self.cast.notify(msg);
     }
 }
diff --git a/nested/src/index/map_key.rs b/nested/src/index/map_key.rs
index b2d450e..19e6916 100644
--- a/nested/src/index/map_key.rs
+++ b/nested/src/index/map_key.rs
@@ -18,9 +18,12 @@ pub use {
     }
 };
 
-impl<SrcKey: 'static, Item: 'static> OuterViewPort<dyn IndexView<SrcKey, Item = Item>> {
+impl<SrcKey, Item> OuterViewPort<dyn IndexView<SrcKey, Item = Item>>
+where SrcKey: Clone + Send + Sync + 'static,
+      Item: 'static
+{
     pub fn map_key<
-        DstKey: 'static,
+        DstKey: Clone + Send + Sync + 'static,
         F1: Fn(&SrcKey) -> DstKey + Send + Sync + 'static,
         F2: Fn(&DstKey) -> Option<SrcKey> + Send + Sync + 'static,
     >(
@@ -29,6 +32,8 @@ impl<SrcKey: 'static, Item: 'static> OuterViewPort<dyn IndexView<SrcKey, Item =
         f2: F2
     ) -> OuterViewPort<dyn IndexView<DstKey, Item = Item>> {
         let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
         let map = MapIndexKey::new(port.inner(), f1, f2);
         self.add_observer(map.clone());
         port.into_outer()
@@ -36,7 +41,9 @@ impl<SrcKey: 'static, Item: 'static> OuterViewPort<dyn IndexView<SrcKey, Item =
 }
 
 pub struct MapIndexKey<DstKey, SrcKey, SrcView, F1, F2>
-where SrcView: IndexView<SrcKey> + ?Sized,
+where DstKey: Clone + Send + Sync,
+      SrcKey: Clone + Send + Sync,
+      SrcView: IndexView<SrcKey> + ?Sized,
       F1: Fn(&SrcKey) -> DstKey + Send + Sync,
       F2: Fn(&DstKey) -> Option<SrcKey> + Send + Sync,
 {
@@ -47,8 +54,8 @@ where SrcView: IndexView<SrcKey> + ?Sized,
 }
 
 impl<DstKey, SrcKey, SrcView, F1, F2> MapIndexKey<DstKey, SrcKey, SrcView, F1, F2>
-where DstKey: 'static,
-      SrcKey: 'static,
+where DstKey: Clone + Send + Sync + 'static,
+      SrcKey: Clone + Send + Sync + 'static,
       SrcView: IndexView<SrcKey> + ?Sized + 'static,
       SrcView::Item: 'static,
       F1: Fn(&SrcKey) -> DstKey + Send + Sync + 'static,
@@ -74,7 +81,9 @@ where DstKey: 'static,
 }
 
 impl<DstKey, SrcKey, SrcView, F1, F2> View for MapIndexKey<DstKey, SrcKey, SrcView, F1, F2>
-where SrcView: IndexView<SrcKey> + ?Sized,
+where DstKey: Clone + Send + Sync,
+      SrcKey: Clone + Send + Sync,
+      SrcView: IndexView<SrcKey> + ?Sized,
       F1: Fn(&SrcKey) -> DstKey + Send + Sync,
       F2: Fn(&DstKey) -> Option<SrcKey> + Send + Sync,
 {
@@ -82,7 +91,9 @@ where SrcView: IndexView<SrcKey> + ?Sized,
 }
 
 impl<DstKey, SrcKey, SrcView, F1, F2> IndexView<DstKey> for MapIndexKey<DstKey, SrcKey, SrcView, F1, F2>
-where SrcView: IndexView<SrcKey> + ?Sized,
+where DstKey: Clone + Send + Sync,
+      SrcKey: Clone + Send + Sync,
+      SrcView: IndexView<SrcKey> + ?Sized,
       F1: Fn(&SrcKey) -> DstKey + Send + Sync,
       F2: Fn(&DstKey) -> Option<SrcKey> + Send + Sync,
 {
@@ -98,7 +109,9 @@ where SrcView: IndexView<SrcKey> + ?Sized,
 }
 
 impl<DstKey, SrcKey, SrcView, F1, F2> Observer<SrcView> for MapIndexKey<DstKey, SrcKey, SrcView, F1, F2>
-where SrcView: IndexView<SrcKey> + ?Sized,
+where DstKey: Clone + Send + Sync,
+      SrcKey: Clone + Send + Sync,
+      SrcView: IndexView<SrcKey> + ?Sized,
       F1: Fn(&SrcKey) -> DstKey + Send + Sync,
       F2: Fn(&DstKey) -> Option<SrcKey> + Send + Sync,
 {
@@ -111,7 +124,7 @@ where SrcView: IndexView<SrcKey> + ?Sized,
         if let Some(area) = new_area { self.cast.notify_each(area); }
     }
 
-    fn notify(&self, msg: &SrcKey) {
+    fn notify(&mut self, msg: &SrcKey) {
         self.cast.notify(&(self.f1)(msg));
     }
 }
diff --git a/nested/src/index/mod.rs b/nested/src/index/mod.rs
index ddf7a99..51d42cf 100644
--- a/nested/src/index/mod.rs
+++ b/nested/src/index/mod.rs
@@ -13,7 +13,8 @@ use {
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-pub trait IndexView<Key> : View<Msg = Key> {
+pub trait IndexView<Key> : View<Msg = Key>
+where Key: Send + Sync {
     type Item;
 
     fn get(&self, key: &Key) -> Option<Self::Item>;
@@ -26,7 +27,10 @@ pub trait IndexView<Key> : View<Msg = Key> {
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-impl<Key, V: IndexView<Key> + ?Sized> IndexView<Key> for RwLock<V> {
+impl<Key, V> IndexView<Key> for RwLock<V>
+where Key: Send + Sync,
+      V: IndexView<Key> + ?Sized
+{
     type Item = V::Item;
 
     fn get(&self, key: &Key) -> Option<Self::Item> {
@@ -38,7 +42,11 @@ impl<Key, V: IndexView<Key> + ?Sized> IndexView<Key> for RwLock<V> {
     }
 }
 
-impl<Key, V: IndexView<Key> + ?Sized> IndexView<Key> for Arc<V> {
+impl<Key, V> IndexView<Key> for Arc<V>
+where Key: Send + Sync,
+      V: IndexView<Key> + ?Sized
+{
+
     type Item = V::Item;
 
     fn get(&self, key: &Key) -> Option<Self::Item> {
@@ -50,7 +58,10 @@ impl<Key, V: IndexView<Key> + ?Sized> IndexView<Key> for Arc<V> {
     }
 }
 
-impl<Key, V: IndexView<Key>> IndexView<Key> for Option<V> {
+impl<Key, V> IndexView<Key> for Option<V>
+where Key: Send + Sync,
+      V: IndexView<Key>
+{
     type Item = V::Item;
 
     fn get(&self, key: &Key) -> Option<Self::Item> {
@@ -69,7 +80,7 @@ impl<Key, V: IndexView<Key>> IndexView<Key> for Option<V> {
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
 pub trait ImplIndexView : Send + Sync {
-    type Key;
+    type Key : Send + Sync;
     type Value;
 
     fn get(&self, key: &Self::Key) -> Option<Self::Value>;
diff --git a/nested/src/integer/add.rs b/nested/src/integer/add.rs
index e093577..49a87bf 100644
--- a/nested/src/integer/add.rs
+++ b/nested/src/integer/add.rs
@@ -53,7 +53,7 @@ impl Add {
         b: OuterViewPort<dyn SequenceView<Item = usize>>,
         c: InnerViewPort<RwLock<Vec<usize>>>//<dyn SequenceView<Item = usize>>
     ) -> Arc<RwLock<Self>> {
-        let mut proj_helper = ProjectionHelper::new();
+        let mut proj_helper = ProjectionHelper::new(c.0.update_hooks.clone());
         let add = Arc::new(RwLock::new(
             Add {
                 radix,
diff --git a/nested/src/integer/radix.rs b/nested/src/integer/radix.rs
index 9f3169c..2176eb0 100644
--- a/nested/src/integer/radix.rs
+++ b/nested/src/integer/radix.rs
@@ -82,7 +82,7 @@ impl Observer<dyn SequenceView<Item = usize>> for RadixProjection {
         self.src_digits = view;
     }
 
-    fn notify(&self, _idx: &usize) {
+    fn notify(&mut self, _idx: &usize) {
         // todo:
         // src digit i changed.
         // which dst-digits does it affect?
diff --git a/nested/src/leveled_term_view.rs b/nested/src/leveled_term_view.rs
index a4d8ff4..1f6b387 100644
--- a/nested/src/leveled_term_view.rs
+++ b/nested/src/leveled_term_view.rs
@@ -35,7 +35,7 @@ impl LeveledTermView {
         src_port: OuterViewPort<dyn TerminalView>,
         dst_port: InnerViewPort<dyn TerminalView>
     ) -> Arc<RwLock<Self>> {
-        let mut proj_helper = ProjectionHelper::new();
+        let mut proj_helper = ProjectionHelper::new(dst_port.0.update_hooks.clone());
 
         let v = Arc::new(RwLock::new(
             LeveledTermView {
diff --git a/nested/src/projection.rs b/nested/src/projection.rs
index 7d1e40f..f33b9f9 100644
--- a/nested/src/projection.rs
+++ b/nested/src/projection.rs
@@ -2,21 +2,19 @@ use {
     std::{
         cmp::{max},
         any::Any,
-        sync::{Arc, Weak},
-    },
-    async_std::{
-        stream::StreamExt
+        sync::{Arc, Weak}
     },
     std::sync::RwLock,
     crate::{
         core::{
             View,
             Observer, ObserverExt,
+            port::UpdateTask,
             OuterViewPort,
             channel::{
-                channel,
+                ChannelSender, ChannelReceiver,
                 ChannelData,
-                ChannelSender
+                channel
             }
         },
         singleton::{SingletonView},
@@ -29,14 +27,16 @@ use {
 
 pub struct ProjectionHelper<P: Send + Sync + 'static> {
     keepalive: Vec<Arc<dyn Any + Send + Sync>>,
-    proj: Arc<RwLock<Weak<RwLock<P>>>>
+    proj: Arc<RwLock<Weak<RwLock<P>>>>,
+    update_hooks: Arc<RwLock<Vec<Arc<dyn UpdateTask>>>>
 }
 
 impl<P: Send + Sync + 'static> ProjectionHelper<P> {
-    pub fn new() -> Self {
+    pub fn new(update_hooks: Arc<RwLock<Vec<Arc<dyn UpdateTask>>>>) -> Self {
         ProjectionHelper {
             keepalive: Vec::new(),
-            proj: Arc::new(RwLock::new(Weak::new()))
+            proj: Arc::new(RwLock::new(Weak::new())),
+            update_hooks
         }
     }
 
@@ -52,6 +52,7 @@ impl<P: Send + Sync + 'static> ProjectionHelper<P> {
         port: OuterViewPort<dyn SingletonView<Item = Item>>,
         notify: impl Fn(&mut P, &()) + Send + Sync + 'static
     ) -> Arc<RwLock<Option<Arc<dyn SingletonView<Item = Item>>>>> {
+        self.update_hooks.write().unwrap().push(Arc::new(port.0.clone()));
         port.add_observer(self.new_arg(notify));
         port.get_view_arc()
     }
@@ -61,6 +62,7 @@ impl<P: Send + Sync + 'static> ProjectionHelper<P> {
         port: OuterViewPort<dyn SequenceView<Item = Item>>,
         notify: impl Fn(&mut P, &usize) + Send + Sync + 'static
     ) -> Arc<RwLock<Option<Arc<dyn SequenceView<Item = Item>>>>> {
+        self.update_hooks.write().unwrap().push(Arc::new(port.0.clone()));
         port.add_observer(self.new_arg(notify));
         port.get_view_arc()
     }
@@ -70,7 +72,10 @@ impl<P: Send + Sync + 'static> ProjectionHelper<P> {
         port: OuterViewPort<dyn IndexView<Key, Item = Item>>,
         notify: impl Fn(&mut P, &Key) + Send + Sync + 'static
     ) -> Arc<RwLock<Option<Arc<dyn IndexView<Key, Item = Item>>>>> {
-        port.add_observer(self.new_arg(notify));
+        self.update_hooks.write().unwrap().push(Arc::new(port.0.clone()));
+
+        let arg = self.new_arg(notify);
+        port.add_observer(arg);
         port.get_view_arc()
     }
 
@@ -79,46 +84,76 @@ impl<P: Send + Sync + 'static> ProjectionHelper<P> {
     >(
         &mut self,
         notify: impl Fn(&mut P, &V::Msg) + Send + Sync + 'static
-    ) -> Arc<RwLock<ProjectionArg<V, Vec<V::Msg>>>>
-    where V::Msg: Send + Sync {
-        let (tx, mut rx) = channel::<Vec<V::Msg>>();
-
+    ) -> Arc<RwLock<ProjectionArg<P, V, Vec<V::Msg>>>>
+    where V::Msg: Send + Sync
+    {
+        let (tx, rx) = channel::<Vec<V::Msg>>();
         let arg = Arc::new(RwLock::new(
             ProjectionArg {
                 src: None,
-                sender: tx
+                notify: Box::new(notify),
+                proj: self.proj.clone(),
+                rx, tx
             }));
 
-        let proj = self.proj.clone();
-        async_std::task::spawn(async move {
-            while let Some(msg) = rx.next().await {
-                if let Some(proj) = proj.read().unwrap().upgrade() {
-                    notify(&mut *proj.write().unwrap(), &msg);
-                }
-            }
-        });
-
         self.keepalive.push(arg.clone());
 
+        self.update_hooks.write().unwrap().push(arg.clone());
         arg
     }
 }
 
 /// Special Observer which can access the state of the projection on notify
-/// also handles the reset() and default behaviour of unitinitalized inputs
-pub struct ProjectionArg<V, D>
-where V: View + ?Sized,
+/// also handles the reset()
+pub struct ProjectionArg<P, V, D>
+where P: Send + Sync + 'static,
+      V: View + ?Sized,
       D: ChannelData<Item = V::Msg>,
       D::IntoIter: Send + Sync
 {
     src: Option<Arc<V>>,
-    sender: ChannelSender<D>
+    notify: Box<dyn Fn(&mut P, &V::Msg) + Send + Sync + 'static>,
+    proj: Arc<RwLock<Weak<RwLock<P>>>>,
+    rx: ChannelReceiver<D>,
+    tx: ChannelSender<D>
+}
+
+impl<P, V, D> UpdateTask for ProjectionArg<P, V, D>
+where P: Send + Sync + 'static,
+      V: View + ?Sized,
+      D: ChannelData<Item = V::Msg>,
+      D::IntoIter: Send + Sync
+{
+    fn update(&self) {        
+        if let Some(p) = self.proj.read().unwrap().upgrade() {
+            if let Some(data) = self.rx.try_recv() {
+                for msg in data {
+                    (self.notify)(
+                        &mut *p.write().unwrap(),
+                        &msg
+                    );
+                }
+            }
+        }
+    }
+}
+
+impl<P, V, D> UpdateTask for RwLock<ProjectionArg<P, V, D>>
+where P: Send + Sync + 'static,
+      V: View + ?Sized,
+      D: ChannelData<Item = V::Msg>,
+      D::IntoIter: Send + Sync
+{
+    fn update(&self) {
+        self.read().unwrap().update();
+    }
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-impl<Item, D> Observer<dyn SingletonView<Item = Item>> for ProjectionArg<dyn SingletonView<Item = Item>, D>
-where D: ChannelData<Item = ()>,
+impl<P, Item, D> Observer<dyn SingletonView<Item = Item>> for ProjectionArg<P, dyn SingletonView<Item = Item>, D>
+where P: Send + Sync + 'static,
+      D: ChannelData<Item = ()>,
       D::IntoIter: Send + Sync
 {
     fn reset(&mut self, new_src: Option<Arc<dyn SingletonView<Item = Item>>>) {
@@ -126,15 +161,16 @@ where D: ChannelData<Item = ()>,
         self.notify(&());
     }
 
-    fn notify(&self, msg: &()) {
-        self.sender.send(*msg);
+    fn notify(&mut self, msg: &()) {
+        self.tx.send(msg.clone());
     }
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-impl<Item, D> Observer<dyn SequenceView<Item = Item>> for ProjectionArg<dyn SequenceView<Item = Item>, D>
-where D: ChannelData<Item = usize>,
+impl<P, Item, D> Observer<dyn SequenceView<Item = Item>> for ProjectionArg<P, dyn SequenceView<Item = Item>, D>
+where P: Send + Sync + 'static,
+      D: ChannelData<Item = usize>,
       D::IntoIter: Send + Sync
 {
     fn reset(&mut self, new_src: Option<Arc<dyn SequenceView<Item = Item>>>) {
@@ -145,15 +181,17 @@ where D: ChannelData<Item = usize>,
         self.notify_each(0 .. max(old_len, new_len));
     }
 
-    fn notify(&self, msg: &usize) {
-        self.sender.send(*msg);
+    fn notify(&mut self, msg: &usize) {
+        self.tx.send(*msg);
     }
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-impl<Key: Clone, Item, D> Observer<dyn IndexView<Key, Item = Item>> for ProjectionArg<dyn IndexView<Key, Item = Item>, D>
-where D: ChannelData<Item = Key>,
+impl<P, Key, Item, D> Observer<dyn IndexView<Key, Item = Item>> for ProjectionArg<P, dyn IndexView<Key, Item = Item>, D>
+where P: Send + Sync + 'static,
+      Key: Clone + Send + Sync,
+      D: ChannelData<Item = Key>,
       D::IntoIter: Send + Sync
 {
     fn reset(&mut self, new_src: Option<Arc<dyn IndexView<Key, Item = Item>>>) {
@@ -165,8 +203,8 @@ where D: ChannelData<Item = Key>,
         if let Some(area) = new_area { self.notify_each(area); }
     }
 
-    fn notify(&self, msg: &Key) {
-        self.sender.send(msg.clone());
+    fn notify(&mut self, msg: &Key) {
+        self.tx.send(msg.clone());
     }
 }
 
diff --git a/nested/src/sequence/filter.rs b/nested/src/sequence/filter.rs
index 0cfba42..77b3938 100644
--- a/nested/src/sequence/filter.rs
+++ b/nested/src/sequence/filter.rs
@@ -18,6 +18,8 @@ impl<V: SequenceView + ?Sized + 'static> OuterViewPort<V>
         P: Fn(&V::Item) -> bool + Send + Sync + 'static
     >(&self, pred: P) -> OuterViewPort<dyn SequenceView<Item = V::Item>> {
         let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
         let filter = Arc::new(RwLock::new(
             Filter {
                 src_view: None,
@@ -115,7 +117,7 @@ where SrcView: SequenceView + ?Sized + 'static,
         if let Some(len) = new_len { self.cast.notify_each(0 .. len); }
     }
 
-    fn notify(&self, idx: &usize) {
+    fn notify(&mut self, idx: &usize) {
         let l = self.len().unwrap_or(0)+1;
         let np = 
             if let Some(x) = self.src_view.get(idx) {
diff --git a/nested/src/sequence/flatten.rs b/nested/src/sequence/flatten.rs
index 30fc68b..4fcedc8 100644
--- a/nested/src/sequence/flatten.rs
+++ b/nested/src/sequence/flatten.rs
@@ -65,7 +65,7 @@ where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
         self.notify_each(0 .. std::cmp::max(old_len, new_len));
     }
 
-    fn notify(&self, chunk_idx: &usize) {
+    fn notify(&mut self, chunk_idx: &usize) {
         self.sender.send(*chunk_idx);
     }
 }
@@ -81,7 +81,7 @@ where V2: SequenceView + ?Sized + 'static
         self.notify_each(0 .. std::cmp::max(old_len, new_len));
     }
 
-    fn notify(&self, idx: &usize) {
+    fn notify(&mut self, idx: &usize) {
         self.sender.send(*idx);
     }
 }
@@ -139,7 +139,7 @@ where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
             while let Some(chunk_idx) = recv.next().await {
                 if let Some(mut chunk_rcv) = f.write().unwrap().update_chunk(chunk_idx) {
                     let f = f.clone();
-                    let cast = cast.clone();
+                    let mut cast = cast.clone();
                     async_std::task::spawn(async move {
                         while let Some(idx) = chunk_rcv.next().await {
                             let mut flat = f.write().unwrap();
diff --git a/nested/src/sequence/map.rs b/nested/src/sequence/map.rs
index 79eb93b..a537fd7 100644
--- a/nested/src/sequence/map.rs
+++ b/nested/src/sequence/map.rs
@@ -21,6 +21,8 @@ impl<Item: 'static> OuterViewPort<dyn SequenceView<Item = Item>> {
         f: F
     ) -> OuterViewPort<dyn SequenceView<Item = DstItem>> {
         let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
         let map = Arc::new(RwLock::new(MapSequenceItem {
             src_view: None,
             f,
@@ -83,7 +85,7 @@ where SrcView: SequenceView + ?Sized,
         if let Some(len) = new_len { self.cast.notify_each(0 .. len ); }
     }
 
-    fn notify(&self, msg: &usize) {
+    fn notify(&mut self, msg: &usize) {
         self.cast.notify(msg);
     }
 }
diff --git a/nested/src/sequence/seq2idx.rs b/nested/src/sequence/seq2idx.rs
index 0967e4e..79cf003 100644
--- a/nested/src/sequence/seq2idx.rs
+++ b/nested/src/sequence/seq2idx.rs
@@ -39,6 +39,7 @@ where SrcView: SequenceView + ?Sized + 'static {
 impl<Item: 'static> OuterViewPort<dyn SequenceView<Item = Item>> {
     pub fn to_index(&self) -> OuterViewPort<dyn IndexView<usize, Item = Item>> {
         let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
         self.add_observer(Sequence2Index::new(port.inner()));
         port.into_outer()
     }
@@ -73,7 +74,7 @@ where SrcView: SequenceView + ?Sized + 'static {
         if let Some(area) = new_area { self.cast.notify_each(area); }
     }
 
-    fn notify(&self, msg: &usize) {
+    fn notify(&mut self, msg: &usize) {
         self.cast.notify(msg);
     }
 }
diff --git a/nested/src/sequence/vec_buffer.rs b/nested/src/sequence/vec_buffer.rs
index 371fcb8..4fba5f9 100644
--- a/nested/src/sequence/vec_buffer.rs
+++ b/nested/src/sequence/vec_buffer.rs
@@ -61,6 +61,8 @@ impl<T> OuterViewPort<RwLock<Vec<T>>>
 where T: Clone + Send + Sync + 'static {
     pub fn to_sequence(&self) -> OuterViewPort<dyn SequenceView<Item = T>> {
         let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
         let vec_seq = VecSequence::new(port.inner());
         self.add_observer(vec_seq.clone());
         port.into_outer()
@@ -114,7 +116,7 @@ where T: Clone + Serialize + Send + Sync + 'static,
         out.flush().expect("");
     }
 
-    fn notify(&self, diff: &VecDiff<T>) {
+    fn notify(&mut self, diff: &VecDiff<T>) {
         let mut out = self.out.write().unwrap();
         out.write(&bincode::serialized_size(diff).unwrap().to_le_bytes()).expect("");
         out.write(&bincode::serialize(diff).unwrap()).expect("");
@@ -142,7 +144,7 @@ where T: Clone + Serialize + Send + Sync + 'static,
         self.out.write().unwrap().flush().expect("");
     }
 
-    fn notify(&self, diff: &VecDiff<T>) {
+    fn notify(&mut self, diff: &VecDiff<T>) {
         self.out.write().unwrap().write(serde_json::to_string(diff).unwrap().as_bytes()).expect("");
         self.out.write().unwrap().write(b"\n").expect("");
         self.out.write().unwrap().flush().expect("");
@@ -184,7 +186,7 @@ where T: Clone + Send + Sync + 'static {
         self.cast.notify_each(0 .. std::cmp::max(old_len, new_len));
     }
 
-    fn notify(&self, diff: &VecDiff<T>) {
+    fn notify(&mut self, diff: &VecDiff<T>) {
         match diff {
             VecDiff::Clear => {
                 let l = {
diff --git a/nested/src/string_editor.rs b/nested/src/string_editor.rs
index 3e610aa..064671e 100644
--- a/nested/src/string_editor.rs
+++ b/nested/src/string_editor.rs
@@ -166,7 +166,7 @@ pub mod insert_view {
             data_port: OuterViewPort<dyn SequenceView<Item = char>>,
             out_port: InnerViewPort<dyn TerminalView>
         ) -> Arc<RwLock<Self>> {
-            let mut proj_helper = ProjectionHelper::new();
+            let mut proj_helper = ProjectionHelper::new(out_port.0.update_hooks.clone());
 
             let proj = Arc::new(RwLock::new(
                 StringInsertView {
diff --git a/nested/src/terminal/compositor.rs b/nested/src/terminal/compositor.rs
index 0efb950..c2d64b3 100644
--- a/nested/src/terminal/compositor.rs
+++ b/nested/src/terminal/compositor.rs
@@ -30,7 +30,7 @@ impl TerminalCompositor {
             TerminalCompositor {
                 layers: Vec::new(),
                 cast: port.get_broadcast(),
-                proj_helper: ProjectionHelper::new()
+                proj_helper: ProjectionHelper::new(port.0.update_hooks.clone())
             }
         ));
 
diff --git a/nested/src/terminal/terminal.rs b/nested/src/terminal/terminal.rs
index eec519b..c7b1d91 100644
--- a/nested/src/terminal/terminal.rs
+++ b/nested/src/terminal/terminal.rs
@@ -135,7 +135,7 @@ impl Observer<dyn TerminalView> for TermOutObserver {
         }
     }
 
-    fn notify(&self, pos: &Point2<i16>) {
+    fn notify(&mut self, pos: &Point2<i16>) {
         self.dirty_pos_tx.send(*pos);
     }
 }