text_input/
text_input.rs

1//! Simple text input support
2//!
3//! Return creates a new line, backspace removes the last character.
4//! Clicking toggle IME (Input Method Editor) support, but the font used as limited support of characters.
5//! You should change the provided font with another one to test other languages input.
6
7use std::mem;
8
9use bevy::{
10    input::keyboard::{Key, KeyboardInput},
11    prelude::*,
12};
13
14fn main() {
15    App::new()
16        .add_plugins(DefaultPlugins)
17        .add_systems(Startup, setup_scene)
18        .add_systems(
19            Update,
20            (
21                toggle_ime,
22                listen_ime_events,
23                listen_keyboard_input_events,
24                bubbling_text,
25            ),
26        )
27        .run();
28}
29
30fn setup_scene(mut commands: Commands, asset_server: Res<AssetServer>) {
31    commands.spawn(Camera2d);
32
33    // The default font has a limited number of glyphs, so use the full version for
34    // sections that will hold text input.
35    let font = asset_server.load("fonts/FiraMono-Medium.ttf");
36
37    commands.spawn((
38        Text::default(),
39        Node {
40            position_type: PositionType::Absolute,
41            top: Val::Px(12.0),
42            left: Val::Px(12.0),
43            ..default()
44        },
45        children![
46            TextSpan::new("Click to toggle IME. Press return to start a new line.\n\n",),
47            TextSpan::new("IME Enabled: "),
48            TextSpan::new("false\n"),
49            TextSpan::new("IME Active:  "),
50            TextSpan::new("false\n"),
51            TextSpan::new("IME Buffer:  "),
52            (
53                TextSpan::new("\n"),
54                TextFont {
55                    font: font.clone(),
56                    ..default()
57                },
58            ),
59        ],
60    ));
61
62    commands.spawn((
63        Text2d::new(""),
64        TextFont {
65            font,
66            font_size: 100.0,
67            ..default()
68        },
69    ));
70}
71
72fn toggle_ime(
73    input: Res<ButtonInput<MouseButton>>,
74    mut window: Single<&mut Window>,
75    status_text: Single<Entity, (With<Node>, With<Text>)>,
76    mut ui_writer: TextUiWriter,
77) {
78    if input.just_pressed(MouseButton::Left) {
79        window.ime_position = window.cursor_position().unwrap();
80        window.ime_enabled = !window.ime_enabled;
81
82        *ui_writer.text(*status_text, 3) = format!("{}\n", window.ime_enabled);
83    }
84}
85
86#[derive(Component)]
87struct Bubble {
88    timer: Timer,
89}
90
91fn bubbling_text(
92    mut commands: Commands,
93    mut bubbles: Query<(Entity, &mut Transform, &mut Bubble)>,
94    time: Res<Time>,
95) {
96    for (entity, mut transform, mut bubble) in bubbles.iter_mut() {
97        if bubble.timer.tick(time.delta()).just_finished() {
98            commands.entity(entity).despawn();
99        }
100        transform.translation.y += time.delta_secs() * 100.0;
101    }
102}
103
104fn listen_ime_events(
105    mut events: EventReader<Ime>,
106    status_text: Single<Entity, (With<Node>, With<Text>)>,
107    mut edit_text: Single<&mut Text2d, (Without<Node>, Without<Bubble>)>,
108    mut ui_writer: TextUiWriter,
109) {
110    for event in events.read() {
111        match event {
112            Ime::Preedit { value, cursor, .. } if !cursor.is_none() => {
113                *ui_writer.text(*status_text, 7) = format!("{value}\n");
114            }
115            Ime::Preedit { cursor, .. } if cursor.is_none() => {
116                *ui_writer.text(*status_text, 7) = "\n".to_string();
117            }
118            Ime::Commit { value, .. } => {
119                edit_text.push_str(value);
120            }
121            Ime::Enabled { .. } => {
122                *ui_writer.text(*status_text, 5) = "true\n".to_string();
123            }
124            Ime::Disabled { .. } => {
125                *ui_writer.text(*status_text, 5) = "false\n".to_string();
126            }
127            _ => (),
128        }
129    }
130}
131
132fn listen_keyboard_input_events(
133    mut commands: Commands,
134    mut events: EventReader<KeyboardInput>,
135    edit_text: Single<(&mut Text2d, &TextFont), (Without<Node>, Without<Bubble>)>,
136) {
137    let (mut text, style) = edit_text.into_inner();
138    for event in events.read() {
139        // Only trigger changes when the key is first pressed.
140        if !event.state.is_pressed() {
141            continue;
142        }
143
144        match (&event.logical_key, &event.text) {
145            (Key::Enter, _) => {
146                if text.is_empty() {
147                    continue;
148                }
149                let old_value = mem::take(&mut **text);
150
151                commands.spawn((
152                    Text2d::new(old_value),
153                    style.clone(),
154                    Bubble {
155                        timer: Timer::from_seconds(5.0, TimerMode::Once),
156                    },
157                ));
158            }
159            (Key::Backspace, _) => {
160                text.pop();
161            }
162            (_, Some(inserted_text)) => {
163                // Make sure the text doesn't have any control characters,
164                // which can happen when keys like Escape are pressed
165                if inserted_text.chars().all(is_printable_char) {
166                    text.push_str(inserted_text);
167                }
168            }
169            _ => continue,
170        }
171    }
172}
173
174// this logic is taken from egui-winit:
175// https://github.com/emilk/egui/blob/adfc0bebfc6be14cee2068dee758412a5e0648dc/crates/egui-winit/src/lib.rs#L1014-L1024
176fn is_printable_char(chr: char) -> bool {
177    let is_in_private_use_area = ('\u{e000}'..='\u{f8ff}').contains(&chr)
178        || ('\u{f0000}'..='\u{ffffd}').contains(&chr)
179        || ('\u{100000}'..='\u{10fffd}').contains(&chr);
180
181    !is_in_private_use_area && !chr.is_ascii_control()
182}
text_input/text_input.rs

text_input/
text_input.rs
