Bevy desktop platform

When to use

Load this when configuring the desktop window, mode, or close behavior. Web and mobile constraints stay on their skills.

ECS shape

• Module: bevy::window is a platform-agnostic window interface. WindowPlugin is part of DefaultPlugins.
• Components: Window is the defining component for window entities. PrimaryWindow marks the primary window.
• Mode: WindowMode, PresentMode, WindowResolution, WindowPosition are enums or structs on that page.
• Backend feature: bevy_winit is the winit window and input backend. x11 and wayland are features.
• Close: exit_on_primary_closed and exit_on_all_closed are named functions. WindowCloseRequested is the event.

Coming from Godot

Godot idea	Bevy idiom
Window size	WindowResolution on the primary Window
Fullscreen	WindowMode::BorderlessFullscreen
Quit on close	ExitCondition::OnPrimaryClosed on WindowPlugin

Scope

x11 and wayland are bevy features. The primary window is configured on WindowPlugin before the app runs. Runtime mode changes write the Window component marked PrimaryWindow.

Examples

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

[dependencies]
bevy = "0.20"

The primary window is 1280 by 720, vsync, and closes the app when that window closes.

use bevy::window::ExitCondition;
use bevy::window::PresentMode;
use bevy::window::WindowMode;
use bevy::window::WindowResolution;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins.set(WindowPlugin {
            primary_window: Some(Window {
                title: "Desktop".into(),
                resolution: WindowResolution::new(1280, 720),
                present_mode: PresentMode::AutoVsync,
                mode: WindowMode::Windowed,
                ..default()
            }),
            exit_condition: ExitCondition::OnPrimaryClosed,
            close_when_requested: true,
            ..default()
        }))
        .run();
}

F11 flips the primary window between windowed and borderless fullscreen on the current monitor.

use bevy::window::MonitorSelection;
use bevy::window::PrimaryWindow;
use bevy::window::WindowMode;

fn toggle_fullscreen(
    keys: Res<ButtonInput<KeyCode>>,
    mut windows: Query<&mut Window, With<PrimaryWindow>>,
) {
    if !keys.just_pressed(KeyCode::F11) {
        return;
    }
    let Ok(mut window) = windows.single_mut() else {
        return;
    };
    window.mode = if window.mode == WindowMode::Windowed {
        WindowMode::BorderlessFullscreen(MonitorSelection::Current)
    } else {
        WindowMode::Windowed
    };
}

A second system reads the live resolution. It does not write Window, so it can run beside the toggle without .chain().

use bevy::window::PrimaryWindow;

fn log_resolution(windows: Query<&Window, With<PrimaryWindow>>) {
    let Ok(window) = windows.single() else {
        return;
    };
    let width = window.resolution.width();
    let height = window.resolution.height();
    let _ = (width, height);
}

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 Godot node script
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 Godot DisplayServer or window project-setting names. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• No Godot types in Bevy code. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• 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 Documentation

• bevy crate - API reference and Cargo feature list.
• 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.
• bevy::window - Window, WindowPlugin, PrimaryWindow, WindowMode.

Related Skills

Prerequisites

• bevy-master - Hub and schedules.
• bevy-ecs-composition - Components and systems.

Complements

• bevy-platform-web - Wasm limits.
• bevy-input-handling - Pointer and keyboard.
• godot-platform-desktop - Equivalent Godot skill.

Downstream / consumers

• None yet.

Master

• bevy-master - Bevy router.