1 files changed, 77 insertions, 0 deletions
diff --git a/src/interface.rs b/src/interface.rs
new file mode 100644
index 00000000..6c4982e5
--- /dev/null
+++ b/src/interface.rs
@@ -0,0 +1,77 @@
+use std::hash::Hasher;
+use stretch::result;
+
+use crate::{Element, Event, Layout, MouseCursor, Point};
+
+pub struct Interface<'a, Message, Renderer> {
+    hash: u64,
+    root: Element<'a, Message, Renderer>,
+    layout: result::Layout,
+}
+
+pub struct Cache {
+    hash: u64,
+    layout: result::Layout,
+}
+
+impl<'a, Message, Renderer> Interface<'a, Message, Renderer> {
+    pub fn compute(
+        root: Element<'a, Message, Renderer>,
+        renderer: &Renderer,
+    ) -> Interface<'a, Message, Renderer> {
+        let hasher = &mut crate::Hasher::default();
+        root.hash(hasher);
+
+        let hash = hasher.finish();
+        let layout = root.compute_layout(renderer);
+
+        Interface { hash, root, layout }
+    }
+
+    pub fn compute_with_cache(
+        root: Element<'a, Message, Renderer>,
+        renderer: &Renderer,
+        cache: Cache,
+    ) -> Interface<'a, Message, Renderer> {
+        let hasher = &mut crate::Hasher::default();
+        root.hash(hasher);
+
+        let hash = hasher.finish();
+
+        let layout = if hash == cache.hash {
+            cache.layout
+        } else {
+            root.compute_layout(renderer)
+        };
+
+        Interface { hash, root, layout }
+    }
+
+    pub fn on_event(&mut self, event: Event, cursor_position: Point, messages: &mut Vec<Message>) {
+        let Interface { root, layout, .. } = self;
+
+        root.widget
+            .on_event(event, Self::layout(layout), cursor_position, messages);
+    }
+
+    pub fn draw(&self, renderer: &mut Renderer, cursor_position: Point) -> MouseCursor {
+        let Interface { root, layout, .. } = self;
+
+        let cursor = root
+            .widget
+            .draw(renderer, Self::layout(layout), cursor_position);
+
+        cursor
+    }
+
+    pub fn cache(self) -> Cache {
+        Cache {
+            hash: self.hash,
+            layout: self.layout,
+        }
+    }
+
+    fn layout(layout: &result::Layout) -> Layout<'_> {
+        Layout::new(layout, Point::new(0.0, 0.0))
+    }
+}