Bevy adapt desktop to mobile

When to use

Load this when a desktop window game must accept touch and a smaller layout. Platform features are on bevy-platform-mobile.

ECS shape

Input: Touches lists active contacts. Action mapping lives on bevy-input-handling.
UI: enlarge Node hit targets and pad the root with a safe-inset Resource. WindowResolution sets the logical size and an optional scale-factor override. WindowScaleFactorChanged reports a live dpi change.
Textures: ASTC is a compressed texture format for mobile GPUs. Upload still goes through Assets<Image>.

fn configure_window(mut windows: Query<&mut Window>) {
    let Ok(mut window) = windows.single_mut() else {
        return;
    };
    window.resolution.set(720.0, 1280.0);
    window.resolution.set_scale_factor_override(Some(2.0));
}

#[derive(Resource, Default)]
struct LastTouch(Option<Vec2>);

fn track_touch(touches: Res<Touches>, mut last: ResMut<LastTouch>) {
    last.0 = touches.iter().next().map(|touch| touch.position());
}

#[derive(Component)]
struct TouchTarget;

#[derive(Component)]
struct HudRoot;

#[derive(Resource)]
struct SafeInsets {
    top: f32,
    bottom: f32,
}

fn enlarge_targets(mut nodes: Query<&mut Node, With<TouchTarget>>) {
    for mut node in &mut nodes {
        node.min_width = Val::Px(88.0);
        node.min_height = Val::Px(88.0);
    }
}

fn pad_hud(insets: Res<SafeInsets>, mut roots: Query<&mut Node, With<HudRoot>>) {
    for mut node in &mut roots {
        node.padding = UiRect {
            top: Val::Px(insets.top),
            bottom: Val::Px(insets.bottom),
            left: Val::Px(12.0),
            right: Val::Px(12.0),
        };
    }
}

use bevy::window::WindowScaleFactorChanged;

fn follow_dpi(
    mut scale_events: MessageReader<WindowScaleFactorChanged>,
    mut ui_scale: ResMut<UiScale>,
) {
    for event in scale_events.read() {
        ui_scale.0 = event.scale_factor as f32;
    }
}

[dependencies]
bevy = "0.20"

Adapt choices

Need	Bevy approach
Pointer	`Touches` for contacts. Pointer position on a desktop window is `Window::cursor_position`.
Hover-only menus	Actions that require a hover state need a pressed or tapped path as well.
Safe margins	`SafeInsets` resource applied as `Node` padding.

Scope

Store listings and OS permission dialogs are outside this skill. Layout, touch, and dpi live in the systems above.
Platform packaging stays on bevy-platform-mobile.

Expert Knowledge Delta

Target: Bevy 0.20+.

Core ECS types: Component, Resource, Query, Commands, Startup, Update, Fixed / FixedMain (bevy::time), .chain(), Plugin, DefaultPlugins, MinimalPlugins. Messages and observers are an ownership slot. See bevy-events-messaging for their APIs. Systems run in parallel unless .chain() orders the ones that conflict.

Who owns state

Piece	Owner	Who may mutate	Schedule
Data on one entity	`Component`	One system via `Query`	`Update` or `FixedMain`
One value for the whole app	`Resource`	One system	`Startup` to insert, then the schedule that reads it
Spawn	`Commands`	The spawning system	`Startup` for the initial world; later schedules for runtime spawn
Order that must not race	`.chain()`	The chained systems only	Same schedule
Plugin boundary	`Plugin`	`build` registers systems and resources	Before the app runs

Borrow rule: two systems that both mutably query the same component must be ordered (.chain()) or split so only one writes. Unrelated systems stay parallel. That is the ECS page rule, not a guess at a system-set API.

Decision

If you need	Do this	Do not
Per-entity data	`Component` + `Query`	A script field copied onto the entity
App-wide config or clock	`Resource`	Copy the value onto every entity
Stable simulation step	`FixedMain` and the `Fixed` clock	Tie simulation to raw frame `Update`
Startup spawn	`Commands` in `Startup`	Spawn from a render system
Cross-system notice that is not shared state	Message or observer slot in `bevy-events-messaging`	A new event type invented in this file
An API outside the documented set	Check the official docs first	A made-up crate or API

Load references/ecs-ownership.md for the ownership table.

NEVER

Do not pin /0.20.0/ in docs URLs. WHY: links stay on latest; the 0.20 target is stated once in prose.
Do not mutably query the same component from two unordered systems. WHY: the schedule runs systems in parallel unless .chain() orders them.
Do not invent a physics, navigation, networking, or XR crate here. WHY: this skill only names documented Bevy crates and modules.
No export-preset or touch-emulation names in Bevy code. WHY: Touches, Window, and UiScale are the documented Bevy pieces.
No invented APIs or unnamed third-party crates as the chosen solver. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

Reference

Official links stay on bevy.org. The library pin on bevy-master stays 0.20.0.

Official Documentation

Assets - Official asset catalog. No third-party crate was selected.
Examples - Example tree on the latest branch.
ECS - Component, systems, Query, Startup, Update, and .chain().
Plugins - Plugin, DefaultPlugins, MinimalPlugins, and add_plugins.

Related Skills

Prerequisites

bevy-master - Hub and schedules.
bevy-ecs-composition - Components and systems.
bevy-platform-mobile - Android and touch features.
bevy-ui-layout - Reflow the HUD.

Complements

bevy-adapt-mobile-to-desktop - The reverse adapt.
godot-adapt-desktop-to-mobile - Same topic on the Godot track.

Downstream / consumers

None yet.

Master

bevy-master - Bevy router.

bevy-adapt-desktop-to-mobile

安装技能