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# Objective - Fixes #10532 ## Solution I've updated the various `Event` send methods to return the sent `EventId`(s). Since these methods previously returned nothing, and this information is cheap to copy, there should be minimal negative consequences to providing this additional information. In the case of `send_batch`, an iterator is returned built from `Range` and `Map`, which only consumes 16 bytes on the stack with no heap allocations for all batch sizes. As such, the cost of this information is negligible. These changes are reflected for `EventWriter` and `World`. For `World`, the return types are optional to account for the possible lack of an `Events` resource. Again, these methods previously returned no information, so its inclusion should only be a benefit. ## Usage Now when sending events, the IDs of those events is available for immediate use: ```rust // Example of a request-response system where the requester can track handled requests. /// A system which can make and track requests fn requester( mut requests: EventWriter<Request>, mut handled: EventReader<Handled>, mut pending: Local<HashSet<EventId<Request>>>, ) { // Check status of previous requests for Handled(id) in handled.read() { pending.remove(&id); } if !pending.is_empty() { error!("Not all my requests were handled on the previous frame!"); pending.clear(); } // Send a new request and remember its ID for later let request_id = requests.send(Request::MyRequest { /* ... */ }); pending.insert(request_id); } /// A system which handles requests fn responder( mut requests: EventReader<Request>, mut handled: EventWriter<Handled>, ) { for (request, id) in requests.read_with_id() { if handle(request).is_ok() { handled.send(Handled(id)); } } } ``` In the above example, a `requester` system can send request events, and keep track of which ones are currently pending by `EventId`. Then, a `responder` system can act on that event, providing the ID as a reference that the `requester` can use. Before this PR, it was not trivial for a system sending events to keep track of events by ID. This is unfortunate, since for a system reading events, it is trivial to access the ID of a event. --- ## Changelog - Updated `Events`: - Added `send_batch` - Modified `send` to return the sent `EventId` - Modified `send_default` to return the sent `EventId` - Updated `EventWriter` - Modified `send_batch` to return all sent `EventId`s - Modified `send` to return the sent `EventId` - Modified `send_default` to return the sent `EventId` - Updated `World` - Modified `send_event` to return the sent `EventId` if sent, otherwise `None`. - Modified `send_event_default` to return the sent `EventId` if sent, otherwise `None`. - Modified `send_event_batch` to return all sent `EventId`s if sent, otherwise `None`. - Added unit test `test_send_events_ids` to ensure returned `EventId`s match the sent `Event`s - Updated uses of modified methods. ## Migration Guide ### `send` / `send_default` / `send_batch` For the following methods: - `Events::send` - `Events::send_default` - `Events::send_batch` - `EventWriter::send` - `EventWriter::send_default` - `EventWriter::send_batch` - `World::send_event` - `World::send_event_default` - `World::send_event_batch` Ensure calls to these methods either handle the returned value, or suppress the result with `;`. ```rust // Now fails to compile due to mismatched return type fn send_my_event(mut events: EventWriter<MyEvent>) { events.send_default() } // Fix fn send_my_event(mut events: EventWriter<MyEvent>) { events.send_default(); } ``` This will most likely be noticed within `match` statements: ```rust // Before match is_pressed { true => events.send(PlayerAction::Fire), // ^--^ No longer returns () false => {} } // After match is_pressed { true => { events.send(PlayerAction::Fire); }, false => {} } ``` --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com> |
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What is Bevy?
Bevy is a refreshingly simple data-driven game engine built in Rust. It is free and open-source forever!
WARNING
Bevy is still in the early stages of development. Important features are missing. Documentation is sparse. A new version of Bevy containing breaking changes to the API is released approximately once every 3 months. We provide migration guides, but we can't guarantee migrations will always be easy. Use only if you are willing to work in this environment.
MSRV: Bevy relies heavily on improvements in the Rust language and compiler. As a result, the Minimum Supported Rust Version (MSRV) is generally close to "the latest stable release" of Rust.
Design Goals
- Capable: Offer a complete 2D and 3D feature set
- Simple: Easy for newbies to pick up, but infinitely flexible for power users
- Data Focused: Data-oriented architecture using the Entity Component System paradigm
- Modular: Use only what you need. Replace what you don't like
- Fast: App logic should run quickly, and when possible, in parallel
- Productive: Changes should compile quickly ... waiting isn't fun
About
- Features: A quick overview of Bevy's features.
- News: A development blog that covers our progress, plans and shiny new features.
Docs
- The Bevy Book: Bevy's official documentation. The best place to start learning Bevy.
- Bevy Rust API Docs: Bevy's Rust API docs, which are automatically generated from the doc comments in this repo.
- Official Examples: Bevy's dedicated, runnable examples, which are great for digging into specific concepts.
- Community-Made Learning Resources: More tutorials, documentation, and examples made by the Bevy community.
Community
Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct.
- Discord: Bevy's official discord server.
- Reddit: Bevy's official subreddit.
- GitHub Discussions: The best place for questions about Bevy, answered right here!
- Bevy Assets: A collection of awesome Bevy projects, tools, plugins and learning materials.
Contributing
If you'd like to help build Bevy, check out the Contributor's Guide. For simple problems, feel free to open an issue or PR and tackle it yourself!
For more complex architecture decisions and experimental mad science, please open an RFC (Request For Comments) so we can brainstorm together effectively!
Getting Started
We recommend checking out The Bevy Book for a full tutorial.
Follow the Setup guide to ensure your development environment is set up correctly. Once set up, you can quickly try out the examples by cloning this repo and running the following commands:
# Switch to the correct version (latest release, default is main development branch)
git checkout latest
# Runs the "breakout" example
cargo run --example breakout
To draw a window with standard functionality enabled, use:
use bevy::prelude::*;
fn main(){
App::new()
.add_plugins(DefaultPlugins)
.run();
}
Fast Compiles
Bevy can be built just fine using default configuration on stable Rust. However for really fast iterative compiles, you should enable the "fast compiles" setup by following the instructions here.
Libraries Used
Bevy is only possible because of the hard work put into these foundational technologies:
- wgpu: modern / low-level / cross-platform graphics library based on the WebGPU API.
- glam-rs: a simple and fast 3D math library for games and graphics
- winit: cross-platform window creation and management in Rust
Bevy Cargo Features
This list outlines the different cargo features supported by Bevy. These allow you to customize the Bevy feature set for your use-case.
Third Party Plugins
Plugins are very welcome to extend Bevy's features. Guidelines are available to help integration and usage.
Thanks and Alternatives
Additionally, we would like to thank the Amethyst, macroquad, coffee, ggez, Fyrox, and Piston projects for providing solid examples of game engine development in Rust. If you are looking for a Rust game engine, it is worth considering all of your options. Each engine has different design goals, and some will likely resonate with you more than others.
This project is tested with BrowserStack.
License
Bevy is free, open source and permissively licensed! Except where noted (below and/or in individual files), all code in this repository is dual-licensed under either:
- MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
at your option. This means you can select the license you prefer! This dual-licensing approach is the de-facto standard in the Rust ecosystem and there are very good reasons to include both.
Some of the engine's code carries additional copyright notices and license terms due to their external origins.
These are generally BSD-like, but exact details vary by crate:
If the README of a crate contains a 'License' header (or similar), the additional copyright notices and license terms applicable to that crate will be listed.
The above licensing requirement still applies to contributions to those crates, and sections of those crates will carry those license terms.
The license field of each crate will also reflect this.
For example, bevy_mikktspace has code under the Zlib license (as well as a copyright notice when choosing the MIT license).
The assets included in this repository (for our examples) typically fall under different open licenses. These will not be included in your game (unless copied in by you), and they are not distributed in the published bevy crates. See CREDITS.md for the details of the licenses of those files.
Your contributions
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.