Support collapsing operations

experiments/2024-12-09/src/app.rs

@@ -102,6 +102,9 @@ impl ApplicationHandler for App {
                     Key::Named(NamedKey::ArrowRight) => {
                         self.view.selected_mut().select_last();
                     }
+                    Key::Named(NamedKey::ArrowLeft) => {
+                        self.view.parent_of_selected_mut().select_none();
+                    }
                     Key::Named(NamedKey::ArrowDown) => {
                         self.view.parent_of_selected_mut().select_next();
                     }

experiments/2024-12-09/src/view.rs

@@ -63,6 +63,10 @@ impl OperationView {
         }
     }
 
+    pub fn select_none(&mut self) {
+        self.selected = None;
+    }
+
     pub fn selected(&self) -> &Self {
         self.selected
             .and_then(|selected| self.children.get(selected))