Better test

tests/egui_tests/tests/snapshots/atom_layout_nesting.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:e43b410ab0a06b40da5ad9c7fd105d11201d44a3afd63fd213429cc39013c0d4
+size 6964

tests/egui_tests/tests/test_atoms.rs

@@ -120,6 +120,56 @@ fn test_button_shortcut_text() {
     harness.snapshot("button_shortcut");
 }
 
+/// A root [`AtomLayout`] (in a [`Frame::canvas`]) that stacks several nested [`AtomLayout`]s
+/// (each in an inactive button frame), one per [`Direction`], to exercise nesting and the
+/// direction setting together.
+#[test]
+fn test_atom_layout_nesting_and_direction() {
+    use egui::widget_style::{Classes, WidgetState};
+    use egui::{Atom, AtomLayout, Direction, Frame};
+
+    let mut harness = HarnessBuilder::default().build_ui(|ui| {
+        let style = ui.style().clone();
+
+        // The frame of an inactive button.
+        let button_frame = style
+            .button_style(&Classes::default(), WidgetState::Inactive)
+            .frame;
+
+        // A nested layout laid out along `direction`, labelled to read in that direction.
+        let row = |direction: Direction| {
+            Atom::layout(
+                AtomLayout::new(("one", "two", "three"))
+                    .direction(direction)
+                    .frame(button_frame.clone()),
+            )
+        };
+
+        // Each axis pair gets the same label order, so the reversed direction visibly flips it
+        // (e.g. `RightToLeft` reads "right to left").
+        AtomLayout::new((
+            // The two horizontal rows stacked into their own `TopDown` layout.
+            Atom::layout(
+                AtomLayout::new((
+                    row(Direction::LeftToRight).atom_grow(true),
+                    row(Direction::RightToLeft).atom_grow(true),
+                ))
+                .direction(Direction::TopDown),
+            )
+            .atom_grow(true),
+            row(Direction::TopDown),
+            row(Direction::BottomUp),
+        ))
+        .direction(Direction::LeftToRight)
+        .frame(Frame::canvas(&style))
+        .show(ui);
+    });
+
+    harness.fit_contents();
+
+    harness.snapshot("atom_layout_nesting");
+}
+
 /// Tests the spacing between galleys.
 /// All of these should look the same.
 #[test]