1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148

//! This example illustrates the [`UiScale`] resource from `bevy_ui`.

use bevy::{color::palettes::css::*, prelude::*, text::TextSettings, utils::Duration};

const SCALE_TIME: u64 = 400;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .insert_resource(TextSettings {
            allow_dynamic_font_size: true,
            ..default()
        })
        .insert_resource(TargetScale {
            start_scale: 1.0,
            target_scale: 1.0,
            target_time: Timer::new(Duration::from_millis(SCALE_TIME), TimerMode::Once),
        })
        .add_systems(Startup, setup)
        .add_systems(
            Update,
            (change_scaling, apply_scaling.after(change_scaling)),
        )
        .run();
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    commands.spawn(Camera2dBundle::default());

    let text_style = TextStyle {
        font: asset_server.load("fonts/FiraMono-Medium.ttf"),
        font_size: 16.,
        color: Color::BLACK,
    };

    commands
        .spawn(NodeBundle {
            style: Style {
                width: Val::Percent(50.0),
                height: Val::Percent(50.0),
                position_type: PositionType::Absolute,
                left: Val::Percent(25.),
                top: Val::Percent(25.),
                justify_content: JustifyContent::SpaceAround,
                align_items: AlignItems::Center,
                ..default()
            },
            background_color: ANTIQUE_WHITE.into(),
            ..default()
        })
        .with_children(|parent| {
            parent
                .spawn(NodeBundle {
                    style: Style {
                        width: Val::Px(40.0),
                        height: Val::Px(40.0),
                        ..default()
                    },
                    background_color: RED.into(),
                    ..default()
                })
                .with_children(|parent| {
                    parent.spawn(TextBundle::from_section("Size!", text_style));
                });
            parent.spawn(NodeBundle {
                style: Style {
                    width: Val::Percent(15.0),
                    height: Val::Percent(15.0),
                    ..default()
                },
                background_color: BLUE.into(),
                ..default()
            });
            parent.spawn(ImageBundle {
                style: Style {
                    width: Val::Px(30.0),
                    height: Val::Px(30.0),
                    ..default()
                },
                image: asset_server.load("branding/icon.png").into(),
                ..default()
            });
        });
}

/// System that changes the scale of the ui when pressing up or down on the keyboard.
fn change_scaling(input: Res<ButtonInput<KeyCode>>, mut ui_scale: ResMut<TargetScale>) {
    if input.just_pressed(KeyCode::ArrowUp) {
        let scale = (ui_scale.target_scale * 2.0).min(8.);
        ui_scale.set_scale(scale);
        info!("Scaling up! Scale: {}", ui_scale.target_scale);
    }
    if input.just_pressed(KeyCode::ArrowDown) {
        let scale = (ui_scale.target_scale / 2.0).max(1. / 8.);
        ui_scale.set_scale(scale);
        info!("Scaling down! Scale: {}", ui_scale.target_scale);
    }
}

#[derive(Resource)]
struct TargetScale {
    start_scale: f32,
    target_scale: f32,
    target_time: Timer,
}

impl TargetScale {
    fn set_scale(&mut self, scale: f32) {
        self.start_scale = self.current_scale();
        self.target_scale = scale;
        self.target_time.reset();
    }

    fn current_scale(&self) -> f32 {
        let completion = self.target_time.fraction();
        let t = ease_in_expo(completion);
        self.start_scale.lerp(self.target_scale, t)
    }

    fn tick(&mut self, delta: Duration) -> &Self {
        self.target_time.tick(delta);
        self
    }

    fn already_completed(&self) -> bool {
        self.target_time.finished() && !self.target_time.just_finished()
    }
}

fn apply_scaling(
    time: Res<Time>,
    mut target_scale: ResMut<TargetScale>,
    mut ui_scale: ResMut<UiScale>,
) {
    if target_scale.tick(time.delta()).already_completed() {
        return;
    }

    ui_scale.0 = target_scale.current_scale();
}

fn ease_in_expo(x: f32) -> f32 {
    if x == 0. {
        0.
    } else {
        2.0f32.powf(5. * x - 5.)
    }
}