Move UI out of storybook2 and into ui2

crates/ui2/src/element_ext.rs

@@ -0,0 +1,18 @@
+use gpui3::Element;
+
+pub trait ElementExt<S: 'static + Send + Sync>: Element<State = S> {
+    /// Applies a given function `then` to the current element if `condition` is true.
+    /// This function is used to conditionally modify the element based on a given condition.
+    /// If `condition` is false, it just returns the current element as it is.
+    fn when(mut self, condition: bool, then: impl FnOnce(Self) -> Self) -> Self
+    where
+        Self: Sized,
+    {
+        if condition {
+            self = then(self);
+        }
+        self
+    }
+}
+
+impl<S: 'static + Send + Sync, E: Element<State = S>> ElementExt<S> for E {}