bevy-adapt-mobile-to-desktop

Imported from thedivergentai/game-dev-agentic-skills (skills/bevy-adapt-mobile-to-desktop/SKILL.md). Install upstream with npx skills add thedivergentai/game-dev-agentic-skills --skill bevy-adapt-mobile-to-desktop. Copyright stays with the author.

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

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

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

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.