Bevy adapt mobile to desktop

When to use

Load this when a touch-first game gains a window, mouse, and keyboard. Window setup is bevy-platform-desktop.

ECS shape

• Window: Window, WindowMode, and PrimaryWindow.
• Input: keyboard, mouse, and gamepad features are named on the crate page and already used by bevy-input-handling.
• Pointer: CursorOptions on the primary window. CursorGrabMode::None, Confined, or Locked.

Desktop choices

Need	Bevy idiom
On-screen buttons	Keyboard and mouse via bevy-input-handling, writing the same intent component.
Wider layout	A wider WindowResolution on the primary Window.
Pointer lock	CursorOptions.grab_mode = CursorGrabMode::Locked and visible = false.

Scope

• Keyboard and mouse write a MoveIntent component. Touch buttons can keep writing that same component.
• Window mode, resolution, present mode, and cursor grab live on the primary window entity.

Examples

[package]
name = "desktop_port"
version = "0.1.0"
edition = "2021"

[dependencies]
bevy = "0.20"

Open a windowed 1920x1080 view and lock the pointer while aiming.

use bevy::window::{
    CursorGrabMode, CursorOptions, MonitorSelection, PresentMode, PrimaryWindow, WindowMode,
    WindowResolution,
};

fn desktop_window(mut windows: Query<&mut Window, With<PrimaryWindow>>) {
    for mut window in &mut windows {
        window.mode = WindowMode::Windowed;
        window.resolution = WindowResolution::new(1920, 1080);
        window.title = "Desktop".to_string();
        window.present_mode = PresentMode::AutoVsync;
    }
}

fn unlock_framerate(mut windows: Query<&mut Window, With<PrimaryWindow>>) {
    for mut window in &mut windows {
        window.present_mode = PresentMode::AutoNoVsync;
    }
}

fn borderless(mut windows: Query<&mut Window, With<PrimaryWindow>>) {
    for mut window in &mut windows {
        window.mode = WindowMode::BorderlessFullscreen(MonitorSelection::Current);
    }
}

#[derive(Component)]
struct Aiming;

fn grab_cursor(
    mut cursors: Query<&mut CursorOptions, With<PrimaryWindow>>,
    aiming: Query<(), With<Aiming>>,
) {
    let locked = !aiming.is_empty();
    for mut cursor in &mut cursors {
        cursor.visible = !locked;
        cursor.grab_mode = if locked {
            CursorGrabMode::Locked
        } else {
            CursorGrabMode::None
        };
    }
}

WASD replaces on-screen sticks. The gameplay system reads MoveIntent, not the key codes.

use bevy::window::{MonitorSelection, PrimaryWindow, VideoModeSelection, WindowMode};

#[derive(Component, Default)]
struct MoveIntent(Vec2);

fn read_wasd(keys: Res<ButtonInput<KeyCode>>, mut intents: Query<&mut MoveIntent>) {
    let mut dir = Vec2::ZERO;
    if keys.pressed(KeyCode::KeyA) {
        dir.x -= 1.0;
    }
    if keys.pressed(KeyCode::KeyD) {
        dir.x += 1.0;
    }
    if keys.pressed(KeyCode::KeyW) {
        dir.y += 1.0;
    }
    if keys.pressed(KeyCode::KeyS) {
        dir.y -= 1.0;
    }
    for mut intent in &mut intents {
        intent.0 = dir;
    }
}

fn toggle_fullscreen(
    keys: Res<ButtonInput<KeyCode>>,
    mut windows: Query<&mut Window, With<PrimaryWindow>>,
) {
    if !keys.just_pressed(KeyCode::F11) {
        return;
    }
    for mut window in &mut windows {
        window.mode = match window.mode {
            WindowMode::Windowed => {
                WindowMode::Fullscreen(MonitorSelection::Primary, VideoModeSelection::Current)
            }
            _ => WindowMode::Windowed,
        };
    }
}

Captured look uses the frame's summed motion.

use bevy::input::mouse::AccumulatedMouseMotion;

#[derive(Component)]
struct LookRig;

fn apply_look(
    motion: Res<AccumulatedMouseMotion>,
    mut rigs: Query<&mut Transform, With<LookRig>>,
) {
    for mut transform in &mut rigs {
        transform.rotate_y(-motion.delta.x * 0.002);
    }
}

pub struct LookPlugin;

impl Plugin for LookPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Update, apply_look);
    }
}

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 value stored off 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 second input path that bypasses MoveIntent. WHY: keyboard, mouse, and touch must write the same component so gameplay stays device-agnostic.

• 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

The library pin on bevy-master stays 0.20.0. Permalinks stay unversioned.

Official Documentation

• Assets - Official asset catalog. No third-party crate was selected.
• Examples - Example tree on the latest branch.
• Window examples - WindowMode, present mode, and pointer grab.
• 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-desktop - Window.
• bevy-input-handling - Keyboard, mouse, gamepad.

Complements

• bevy-adapt-desktop-to-mobile - The reverse adapt.

Downstream / consumers

• None yet.

Master

• bevy-master - Bevy router.