⚠️ Improved menu based on egui::Popup (#5716)

Continuation of #5713

**Silently breaking changes:**
- Menus now close on click by default, this is configurable via
`PopupCloseBehavior`

**Additional additions:**
- `Button::right_text`
- `StyleModifier`

This is a rewrite of the egui menus, with the following goals:
- submenu buttons should work everywhere, in a popup, context menu,
area, in some random Ui
- remove the menu state from Ui
- should work just like the previous menu
- ~proper support for keyboard navigation~
  - It's better now but requires further work to be perfect
- support `PopupCloseBehavior`

* Closes #4607 
* [x] I have followed the instructions in the PR template

crates/egui_kittest/tests/menu.rs

@@ -0,0 +1,188 @@
+use egui::containers::menu::{Bar, MenuConfig, SubMenuButton};
+use egui::{include_image, PopupCloseBehavior, Ui};
+use egui_kittest::{Harness, SnapshotResults};
+use kittest::Queryable;
+
+struct TestMenu {
+    config: MenuConfig,
+    checked: bool,
+}
+
+impl TestMenu {
+    fn new(config: MenuConfig) -> Self {
+        Self {
+            config,
+            checked: false,
+        }
+    }
+
+    fn ui(&mut self, ui: &mut Ui) {
+        ui.vertical(|ui| {
+            Bar::new().config(self.config.clone()).ui(ui, |ui| {
+                egui::Sides::new().show(
+                    ui,
+                    |ui| {
+                        ui.menu_button("Menu A", |ui| {
+                            _ = ui.button("Button in Menu A");
+                            ui.menu_button("Submenu A", |ui| {
+                                for i in 0..4 {
+                                    _ = ui.button(format!("Button {i} in Submenu A"));
+                                }
+                            });
+                            ui.menu_image_text_button(
+                                include_image!("../../eframe/data/icon.png"),
+                                "Submenu B with icon",
+                                |ui| {
+                                    _ = ui.button("Button in Submenu B");
+                                },
+                            );
+                            SubMenuButton::new("Submenu C (CloseOnClickOutside)")
+                                .config(
+                                    MenuConfig::new()
+                                        .close_behavior(PopupCloseBehavior::CloseOnClickOutside),
+                                )
+                                .ui(ui, |ui| {
+                                    _ = ui.button("Button in Submenu C");
+                                    ui.checkbox(&mut self.checked, "Checkbox in Submenu C");
+                                    ui.menu_button("Submenu D", |ui| {
+                                        if ui
+                                            .button("Button in Submenu D (close on click)")
+                                            .clicked()
+                                        {
+                                            ui.close();
+                                        };
+                                    });
+                                });
+                        });
+                        ui.menu_image_text_button(
+                            include_image!("../../eframe/data/icon.png"),
+                            "Menu B with icon",
+                            |ui| {
+                                _ = ui.button("Button in Menu B");
+                            },
+                        );
+                        _ = ui.button("Menu Button");
+                        ui.menu_button("Menu C", |ui| {
+                            _ = ui.button("Button in Menu C");
+                        });
+                    },
+                    |ui| {
+                        ui.label("Some other label");
+                    },
+                );
+            });
+        });
+    }
+
+    fn into_harness(self) -> Harness<'static, Self> {
+        Harness::builder()
+            .with_size(egui::Vec2::new(500.0, 300.0))
+            .build_ui_state(
+                |ui, menu| {
+                    egui_extras::install_image_loaders(ui.ctx());
+                    menu.ui(ui);
+                },
+                self,
+            )
+    }
+}
+
+#[test]
+fn menu_close_on_click_outside() {
+    // We're intentionally setting CloseOnClick here so we can test if a submenu can override the
+    // close behavior. (Note how Submenu C has CloseOnClickOutside set)
+    let mut harness =
+        TestMenu::new(MenuConfig::new().close_behavior(PopupCloseBehavior::CloseOnClick))
+            .into_harness();
+
+    harness.get_by_label("Menu A").simulate_click();
+    harness.run();
+
+    harness
+        .get_by_label("Submenu C (CloseOnClickOutside)")
+        .hover();
+    harness.run();
+
+    // We should be able to check the checkbox without closing the menu
+    // Click a couple of times, just in case
+    for expect_checked in [true, false, true, false] {
+        harness
+            .get_by_label("Checkbox in Submenu C")
+            .simulate_click();
+        harness.run();
+        assert_eq!(expect_checked, harness.state().checked);
+    }
+
+    // Hovering outside should not close the menu
+    harness.get_by_label("Some other label").hover();
+    harness.run();
+    assert!(harness.query_by_label("Checkbox in Submenu C").is_some());
+
+    // Clicking outside should close the menu
+    harness.get_by_label("Some other label").simulate_click();
+    harness.run();
+    assert!(harness.query_by_label("Checkbox in Submenu C").is_none());
+}
+
+#[test]
+fn menu_close_on_click() {
+    let mut harness =
+        TestMenu::new(MenuConfig::new().close_behavior(PopupCloseBehavior::CloseOnClick))
+            .into_harness();
+
+    harness.get_by_label("Menu A").simulate_click();
+    harness.run();
+
+    harness.get_by_label("Submenu B with icon").hover();
+    harness.run();
+
+    // Clicking the button should close the menu (even if ui.close() is not called by the button)
+    harness.get_by_label("Button in Submenu B").simulate_click();
+    harness.run();
+    assert!(harness.query_by_label("Button in Submenu B").is_none());
+}
+
+#[test]
+fn clicking_submenu_button_should_never_close_menu() {
+    // We test for this since otherwise the menu wouldn't work on touch devices
+    // The other tests use .hover to open submenus, but this test explicitly uses .simulate_click
+    let mut harness =
+        TestMenu::new(MenuConfig::new().close_behavior(PopupCloseBehavior::CloseOnClick))
+            .into_harness();
+
+    harness.get_by_label("Menu A").simulate_click();
+    harness.run();
+
+    // Clicking the submenu button should not close the menu
+    harness.get_by_label("Submenu B with icon").simulate_click();
+    harness.run();
+
+    harness.get_by_label("Button in Submenu B").simulate_click();
+    harness.run();
+    assert!(harness.query_by_label("Button in Submenu B").is_none());
+}
+
+#[test]
+fn menu_snapshots() {
+    let mut harness = TestMenu::new(MenuConfig::new()).into_harness();
+
+    let mut results = SnapshotResults::new();
+
+    harness.get_by_label("Menu A").hover();
+    harness.run();
+    results.add(harness.try_snapshot("menu/closed_hovered"));
+
+    harness.get_by_label("Menu A").simulate_click();
+    harness.run();
+    results.add(harness.try_snapshot("menu/opened"));
+
+    harness
+        .get_by_label("Submenu C (CloseOnClickOutside)")
+        .hover();
+    harness.run();
+    results.add(harness.try_snapshot("menu/submenu"));
+
+    harness.get_by_label("Submenu D").hover();
+    harness.run();
+    results.add(harness.try_snapshot("menu/subsubmenu"));
+}

crates/egui_kittest/tests/snapshots/menu/closed_hovered.png

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crates/egui_kittest/tests/snapshots/menu/opened.png

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crates/egui_kittest/tests/snapshots/menu/submenu.png

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crates/egui_kittest/tests/snapshots/menu/subsubmenu.png

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