3 files changed, 44 insertions, 0 deletions
diff --git a/web/src/hasher.rs b/web/src/hasher.rs
new file mode 100644
index 00000000..9ce2f7be
--- /dev/null
+++ b/web/src/hasher.rs
@@ -0,0 +1,21 @@
+use std::collections::hash_map::DefaultHasher;
+
+/// The hasher used to compare layouts.
+#[derive(Debug)]
+pub struct Hasher(DefaultHasher);
+
+impl Default for Hasher {
+    fn default() -> Self {
+        Hasher(DefaultHasher::default())
+    }
+}
+
+impl core::hash::Hasher for Hasher {
+    fn write(&mut self, bytes: &[u8]) {
+        self.0.write(bytes)
+    }
+
+    fn finish(&self) -> u64 {
+        self.0.finish()
+    }
+}
diff --git a/web/src/lib.rs b/web/src/lib.rs
index 782bcf93..d4c422d2 100644
--- a/web/src/lib.rs
+++ b/web/src/lib.rs
@@ -61,18 +61,22 @@ use std::{cell::RefCell, rc::Rc};
 
 mod bus;
 mod element;
+mod hasher;
 
 pub mod style;
+pub mod subscription;
 pub mod widget;
 
 pub use bus::Bus;
 pub use dodrio;
 pub use element::Element;
+pub use hasher::Hasher;
 pub use iced_core::{
     Align, Background, Color, Command, Font, HorizontalAlignment, Length,
     VerticalAlignment,
 };
 pub use style::Style;
+pub use subscription::Subscription;
 pub use widget::*;
 
 /// An interactive web application.
diff --git a/web/src/subscription.rs b/web/src/subscription.rs
new file mode 100644
index 00000000..4638c8ab
--- /dev/null
+++ b/web/src/subscription.rs
@@ -0,0 +1,19 @@
+//! Listen to external events in your application.
+use crate::Hasher;
+
+/// A request to listen to external events.
+///
+/// Besides performing async actions on demand with [`Command`], most
+/// applications also need to listen to external events passively.
+///
+/// A [`Subscription`] is normally provided to some runtime, like a [`Command`],
+/// and it will generate events as long as the user keeps requesting it.
+///
+/// For instance, you can use a [`Subscription`] to listen to a WebSocket
+/// connection, keyboard presses, mouse events, time ticks, etc.
+///
+/// [`Command`]: ../struct.Command.html
+/// [`Subscription`]: struct.Subscription.html
+pub type Subscription<T> = iced_core::Subscription<Hasher, (), T>;
+
+pub use iced_core::subscription::Recipe;