Add atoms() helpers to get Atoms from widgets (#8128)

A get atoms trait for Button, checkbox etc. I made it because I had time
to kill after I tried sorting buttons in a Vec by the image in their
atoms, but couldn't get to it because it was private.

---------

Co-authored-by: Lucas Meurer <hi@lucasmerlin.me>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/egui/src/widgets/button.rs

@@ -1,9 +1,9 @@
 use epaint::Margin;
 
 use crate::{
-    Atom, AtomExt as _, AtomKind, AtomLayout, AtomLayoutResponse, Color32, CornerRadius, Frame,
+    Atom, AtomExt as _, AtomKind, AtomLayout, AtomLayoutResponse, Atoms, Color32, CornerRadius,
-    Image, IntoAtoms, NumExt as _, Response, Sense, Stroke, TextStyle, TextWrapMode, Ui, Vec2,
+    Frame, Image, IntoAtoms, NumExt as _, Response, Sense, Stroke, TextStyle, TextWrapMode, Ui,
-    Widget, WidgetInfo, WidgetText, WidgetType,
+    Vec2, Widget, WidgetInfo, WidgetText, WidgetType,
     widget_style::{ButtonStyle, Classes, HasClasses, SELECTED_CLASS, WidgetState},
 };
 
@@ -279,6 +279,13 @@ impl<'a> Button<'a> {
         self
     }
 
+    /// Output the button's [`Atoms`].
+    ///
+    /// This includes any images you have on the button.
+    pub fn atoms(&self) -> &Atoms<'a> {
+        &self.layout.atoms
+    }
+
     /// Show the button and return a [`AtomLayoutResponse`] for painting custom contents.
     pub fn atom_ui(self, ui: &mut Ui) -> AtomLayoutResponse {
         let Button {

crates/egui/src/widgets/checkbox.rs

@@ -41,6 +41,13 @@ impl<'a> Checkbox<'a> {
         Self::new(checked, ())
     }
 
+    /// Output the checkbox's [`Atoms`].
+    ///
+    /// This includes any images you have on the checkbox.
+    pub fn atoms(&self) -> &Atoms<'a> {
+        &self.atoms
+    }
+
     /// Display an indeterminate state (neither checked nor unchecked)
     ///
     /// This only affects the checkbox's appearance. It will still toggle its boolean value when

crates/egui/src/widgets/drag_value.rs

@@ -409,6 +409,13 @@ impl<'a> DragValue<'a> {
         self.update_while_editing = update;
         self
     }
+
+    /// Output the [`DragValue`]'s [`Atoms`].
+    ///
+    /// This includes any images you have on the [`DragValue`].
+    pub fn atoms(&self) -> &Atoms<'a> {
+        &self.atoms
+    }
 }
 
 impl Widget for DragValue<'_> {

crates/egui/src/widgets/radio_button.rs

@@ -35,6 +35,13 @@ impl<'a> RadioButton<'a> {
             atoms: atoms.into_atoms(),
         }
     }
+
+    /// Output the [`RadioButton`]'s [`Atoms`].
+    ///
+    /// This includes any images you have on the [`RadioButton`].
+    pub fn atoms(&self) -> &Atoms<'a> {
+        &self.atoms
+    }
 }
 
 impl Widget for RadioButton<'_> {