From 7fd54ef741d55232f7ab107eec293b3bc894a278 Mon Sep 17 00:00:00 2001
From: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
Date: Sun, 2 Aug 2026 12:22:59 -0700
Subject: [PATCH] Add `BoxedWidget`: dynamically dispatched widgets (#8378)

## Summary

- Add `BoxedWidget` and `Widget::boxed` for heterogeneous widget
collections.
---
 crates/egui/src/widgets/mod.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/crates/egui/src/widgets/mod.rs b/crates/egui/src/widgets/mod.rs
index 21346d64a..ea2e17046 100644
--- a/crates/egui/src/widgets/mod.rs
+++ b/crates/egui/src/widgets/mod.rs
@@ -6,6 +6,12 @@
 
 use crate::{Response, Ui};
 
+/// A dynamically dispatched [`Widget`].
+///
+/// [`Widget`] is not dyn compatible because [`Widget::ui`] takes `self` by value.
+/// This alias uses a closure, which implements [`Widget`].
+pub type BoxedWidget<'a> = Box<dyn FnOnce(&mut Ui) -> Response + 'a>;
+
 mod button;
 mod checkbox;
 pub mod color_picker;
@@ -63,6 +69,20 @@ pub trait Widget {
     ///
     /// Tip: you can `impl Widget for &mut YourObject { }`.
     fn ui(self, ui: &mut Ui) -> Response;
+
+    /// Box this widget for dynamic dispatch.
+    #[inline]
+    fn boxed<'a>(self) -> BoxedWidget<'a>
+    where
+        Self: Sized + 'a,
+    {
+        Box::new(move |ui: &mut Ui| ui.add(self))
+    }
+}
+
+#[test]
+fn widgets_can_be_boxed() {
+    let _: BoxedWidget<'static> = Button::new("boxed").boxed();
 }
 
 /// This enables functions that return `impl Widget`, so that you can