新的缩放系统

use bevy::prelude::*;

const VIRTUAL_WIDTH: f32 = 1920.0;
const VIRTUAL_HEIGHT: f32 = 1080.0;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .add_systems(Update, update_ui_scale)
        .run();
}

fn setup(mut commands: Commands) {
    // 相机
    commands.spawn((Camera2d, Camera::default()));
    
    // UI 根容器
    commands
        .spawn((
            Node {
                width: Val::Percent(100.0),
                height: Val::Percent(100.0),
                justify_content: JustifyContent::Center,
                align_items: AlignItems::Center,
                ..default()
            },
            BackgroundColor(Color::BLACK),
        ))
        .with_children(|parent| {
            // 固定尺寸的内容区域
            parent
                .spawn((
                    Node {
                        width: Val::Px(VIRTUAL_WIDTH),
                        height: Val::Px(VIRTUAL_HEIGHT),
                        flex_direction: FlexDirection::Column,
                        justify_content: JustifyContent::Center,
                        align_items: AlignItems::Center,
                        ..default()
                    },
                    BackgroundColor(Color::srgb(0.2, 0.2, 0.2)),
                ))
                .with_children(|parent| {
                    // 示例 UI 元素 - 固定位置的按钮
                    parent.spawn((
                        Node {
                            width: Val::Px(200.0),
                            height: Val::Px(80.0),
                            position_type: PositionType::Absolute,
                            left: Val::Px(100.0),
                            top: Val::Px(100.0),
                            justify_content: JustifyContent::Center,
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        BackgroundColor(Color::srgb(0.8, 0.2, 0.2)),
                    ))
                    .with_children(|parent| {
                        parent.spawn((
                            Text::new("固定按钮"),
                            TextFont {
                                font_size: 24.0,
                                ..default()
                            },
                            TextColor(Color::WHITE),
                        ));
                    });
                    
                    // 另一个固定位置的 UI 元素
                    parent.spawn((
                        Node {
                            width: Val::Px(150.0),
                            height: Val::Px(60.0),
                            position_type: PositionType::Absolute,
                            right: Val::Px(50.0),
                            bottom: Val::Px(50.0),
                            justify_content: JustifyContent::Center,
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        BackgroundColor(Color::srgb(0.2, 0.8, 0.2)),
                    ))
                    .with_children(|parent| {
                        parent.spawn((
                            Text::new("右下角"),
                            TextFont {
                                font_size: 20.0,
                                ..default()
                            },
                            TextColor(Color::WHITE),
                        ));
                    });
                    
                    // 标题文本
                    parent.spawn((
                        Text::new("固定布局 UI 系统"),
                        TextFont {
                            font_size: 48.0,
                            ..default()
                        },
                        TextColor(Color::WHITE),
                    ));
                });
        });
}

fn update_ui_scale(
    windows: Query<&Window>,
    mut ui_scale: ResMut<UiScale>,
) {
    if let Some(window) = windows.iter().next() {
        let window_width = window.width();
        let window_height = window.height();
        
        // 计算缩放比例，保持宽高比
        let scale_x = window_width / VIRTUAL_WIDTH;
        let scale_y = window_height / VIRTUAL_HEIGHT;
        let scale = scale_x.min(scale_y);
        
        ui_scale.0 = scale;
    }
}