From f04c0ef68927edc40cd1c3a4479b80b9e0c9ca7c Mon Sep 17 00:00:00 2001
From: ickshonpe <david.curthoys@googlemail.com>
Date: Mon, 26 May 2025 21:20:00 +0100
Subject: [PATCH] `tab_navigation` example improvements (#19239)

# Objective

Improve the `tab_navigation` example.

## Solution

* Set different `TabIndex`s for the buttons of each group.
* Label each button with its associated `TabIndex`.
* Reduce the code duplication using a loop.

I tried to flatten it further using the new spawning APIs and
`children!` macro but not sure what the current best way to attach the
observers is.
---
 examples/ui/tab_navigation.rs | 192 +++++++++++-----------------------
 1 file changed, 62 insertions(+), 130 deletions(-)

diff --git a/examples/ui/tab_navigation.rs b/examples/ui/tab_navigation.rs
index 0924269353..25e43cf0be 100644
--- a/examples/ui/tab_navigation.rs
+++ b/examples/ui/tab_navigation.rs
@@ -26,31 +26,21 @@ const PRESSED_BUTTON: Color = Color::srgb(0.35, 0.75, 0.35);
 
 fn button_system(
     mut interaction_query: Query<
-        (
-            &Interaction,
-            &mut BackgroundColor,
-            &mut BorderColor,
-            &Children,
-        ),
+        (&Interaction, &mut BackgroundColor, &mut BorderColor),
         (Changed<Interaction>, With<Button>),
     >,
-    mut text_query: Query<&mut Text>,
 ) {
-    for (interaction, mut color, mut border_color, children) in &mut interaction_query {
-        let mut text = text_query.get_mut(children[0]).unwrap();
+    for (interaction, mut color, mut border_color) in &mut interaction_query {
         match *interaction {
             Interaction::Pressed => {
-                **text = "Press".to_string();
                 *color = PRESSED_BUTTON.into();
                 *border_color = BorderColor::all(RED.into());
             }
             Interaction::Hovered => {
-                **text = "Hover".to_string();
                 *color = HOVERED_BUTTON.into();
                 *border_color = BorderColor::all(Color::WHITE);
             }
             Interaction::None => {
-                **text = "Button".to_string();
                 *color = NORMAL_BUTTON.into();
                 *border_color = BorderColor::all(Color::BLACK);
             }
@@ -78,7 +68,7 @@ fn focus_system(
     }
 }
 
-fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
+fn setup(mut commands: Commands) {
     // ui camera
     commands.spawn(Camera2d);
     commands
@@ -89,6 +79,7 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
             flex_direction: FlexDirection::Column,
             align_items: AlignItems::Center,
             justify_content: JustifyContent::Center,
+            row_gap: Val::Px(6.0),
             ..default()
         })
         .observe(
@@ -98,124 +89,65 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
             },
         )
         .with_children(|parent| {
-            parent.spawn(Text::new("Tab Group 0"));
-            parent
-                .spawn((
-                    Node {
-                        display: Display::Flex,
-                        flex_direction: FlexDirection::Row,
-                        column_gap: Val::Px(6.0),
-                        margin: UiRect {
-                            bottom: Val::Px(10.0),
+            for (label, tab_group, indices) in [
+                // In this group all the buttons have the same `TabIndex` so they will be visited according to their order as children.
+                ("TabGroup 0", TabGroup::new(0), [0, 0, 0, 0]),
+                // In this group the `TabIndex`s are reversed so the buttons will be visited in right-to-left order.
+                ("TabGroup 2", TabGroup::new(2), [3, 2, 1, 0]),
+                // In this group the orders of the indices and buttons match so the buttons will be visited in left-to-right order.
+                ("TabGroup 1", TabGroup::new(1), [0, 1, 2, 3]),
+                // Visit the modal group's buttons in an arbitrary order.
+                ("Modal TabGroup", TabGroup::modal(), [0, 3, 1, 2]),
+            ] {
+                parent.spawn(Text::new(label));
+                parent
+                    .spawn((
+                        Node {
+                            display: Display::Flex,
+                            flex_direction: FlexDirection::Row,
+                            column_gap: Val::Px(6.0),
+                            margin: UiRect {
+                                bottom: Val::Px(10.0),
+                                ..default()
+                            },
                             ..default()
                         },
-                        ..default()
-                    },
-                    TabGroup::new(0),
-                ))
-                .with_children(|parent| {
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                });
-
-            parent.spawn(Text::new("Tab Group 2"));
-            parent
-                .spawn((
-                    Node {
-                        display: Display::Flex,
-                        flex_direction: FlexDirection::Row,
-                        column_gap: Val::Px(6.0),
-                        margin: UiRect {
-                            bottom: Val::Px(10.0),
-                            ..default()
-                        },
-                        ..default()
-                    },
-                    TabGroup::new(2),
-                ))
-                .with_children(|parent| {
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                });
-
-            parent.spawn(Text::new("Tab Group 1"));
-            parent
-                .spawn((
-                    Node {
-                        display: Display::Flex,
-                        flex_direction: FlexDirection::Row,
-                        column_gap: Val::Px(6.0),
-                        margin: UiRect {
-                            bottom: Val::Px(10.0),
-                            ..default()
-                        },
-                        ..default()
-                    },
-                    TabGroup::new(1),
-                ))
-                .with_children(|parent| {
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                });
-
-            parent.spawn(Text::new("Modal Tab Group"));
-            parent
-                .spawn((
-                    Node {
-                        display: Display::Flex,
-                        flex_direction: FlexDirection::Row,
-                        column_gap: Val::Px(6.0),
-                        ..default()
-                    },
-                    TabGroup::modal(),
-                ))
-                .with_children(|parent| {
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                    create_button(parent, &asset_server);
-                });
+                        tab_group,
+                    ))
+                    .with_children(|parent| {
+                        for i in indices {
+                            parent
+                                .spawn((
+                                    Button,
+                                    Node {
+                                        width: Val::Px(200.0),
+                                        height: Val::Px(65.0),
+                                        border: UiRect::all(Val::Px(5.0)),
+                                        justify_content: JustifyContent::Center,
+                                        align_items: AlignItems::Center,
+                                        ..default()
+                                    },
+                                    BorderColor::all(Color::BLACK),
+                                    BackgroundColor(NORMAL_BUTTON),
+                                    TabIndex(i),
+                                    children![(
+                                        Text::new(format!("TabIndex {}", i)),
+                                        TextFont {
+                                            font_size: 20.0,
+                                            ..default()
+                                        },
+                                        TextColor(Color::srgb(0.9, 0.9, 0.9)),
+                                    )],
+                                ))
+                                .observe(
+                                    |mut trigger: Trigger<Pointer<Click>>,
+                                    mut focus: ResMut<InputFocus>| {
+                                        focus.0 = Some(trigger.target());
+                                        trigger.propagate(false);
+                                    },
+                                );
+                        }
+                    });
+            }
         });
 }
-
-fn create_button(parent: &mut ChildSpawnerCommands<'_>, asset_server: &AssetServer) {
-    parent
-        .spawn((
-            Button,
-            Node {
-                width: Val::Px(150.0),
-                height: Val::Px(65.0),
-                border: UiRect::all(Val::Px(5.0)),
-                // horizontally center child text
-                justify_content: JustifyContent::Center,
-                // vertically center child text
-                align_items: AlignItems::Center,
-                ..default()
-            },
-            BorderColor::all(Color::BLACK),
-            BorderRadius::MAX,
-            BackgroundColor(NORMAL_BUTTON),
-            TabIndex(0),
-        ))
-        .observe(
-            |mut trigger: Trigger<Pointer<Click>>, mut focus: ResMut<InputFocus>| {
-                focus.0 = Some(trigger.target());
-                trigger.propagate(false);
-            },
-        )
-        .with_child((
-            Text::new("Button"),
-            TextFont {
-                font: asset_server.load("fonts/FiraSans-Bold.ttf"),
-                font_size: 23.0,
-                ..default()
-            },
-            TextColor(Color::srgb(0.9, 0.9, 0.9)),
-        ));
-}