Add `no_std` support to `bevy_app` by bushrat011899 · Pull Request #16874 · bevyengine/bevy

bushrat011899 · 2024-12-17T23:31:46Z

Objective

Contributes to Tracking Issue: MVP no_std Bevy #15460

Solution

Added the following features:
- std (default)
- bevy_tasks (default)
- downcast (default)
- portable-atomic
- critical-section
downcast and bevy_tasks are now optional dependencies for bevy_app.

Testing

CI
Personal UEFI and Raspberry Pi Pico demo applications compile and run against this branch

Draft Release Notes

Bevy's application framework now supports no_std platforms.

Following up on bevy_ecs gaining no_std support, bevy_app extends the functionality available on these targets to include the powerful App and Plugin abstractions. With this, library authors now have the option of making their plugins no_std compatible, or even offering plugins specifically to improve Bevy on certain embedded platforms!

To start making a no_std compatible plugin, simply disable default features when including bevy_app:

[dependencies]
bevy_app = { version = "0.16", default-features = false }

We encourage library authors to do this anyway, as it can also help with compile times and binary size on all platforms.

Keep an eye out for future no_std updates as we continue to improve the parity between std and no_std. We look forward to seeing what kinds of applications are now possible with Bevy!

Notes

downcast-rs is optional as it isn't compatible with portable-atomic. I will investigate making a PR upstream to add support for this functionality, as it should be very straightforward.
In line with the bevy_ecs no-std-ification, I've added documentation to all features, and grouped them as well.
~~Creating this PR in draft while CI runs and so I can polish before review.~~

bushrat011899 · 2024-12-18T00:05:32Z

crates/bevy_ecs/Cargo.toml

-  "bevy_tasks/portable-atomic",
+  "bevy_tasks?/portable-atomic",
  "concurrent-queue/portable-atomic",
+  "spin/portable_atomic",


The changes to bevy_ecs/Cargo.toml could be split into their own PR, but for now I'm just including them here for brevity. I'm happy to split it out if anyone has any concerns.

bushrat011899 · 2024-12-18T00:07:46Z

tools/ci/src/commands/compile_check_no_std.rs

+        commands.push(PreparedCommand::new::<Self>(
+            cmd!(
+                sh,
+                "cargo check -p bevy_app --no-default-features --features bevy_reflect --target {target}"


Now that bevy_app is compatible, we can start looking into replacing/augmenting this compile_check_no_std CI task with something more robust and tangible, like a no_std example crate.

bushrat011899 · 2024-12-18T00:09:32Z

crates/bevy_app/src/schedule_runner.rs

-                                Ok(Some(delay)) => std::thread::sleep(delay),
+                                Ok(Some(_delay)) => {
+                                    #[cfg(feature = "std")]
+                                    std::thread::sleep(_delay);


Without access to std::thread::sleep, no_std apps will run as-fast-as-possible by default. This isn't ideal, but I believe a reasonable compromise.

bushrat011899 · 2024-12-18T00:12:17Z

crates/bevy_app/src/schedule_runner.rs

+#[cfg(any(target_arch = "wasm32", feature = "std"))]
+use bevy_utils::Instant;


I'm not a fan of how we bring this Instant in. I think it'd be worth considering some kind of bevy_platform_support crate which moves things like spin, portable-atomic, critical-section, wasm-time, etc. into a single spot. It'd be more focussed than bevy_utils, and possibly clean up some of the cfg(...) noise we have across Bevy.

Yes please!

bushrat011899 · 2024-12-18T00:16:39Z

crates/bevy_app/src/plugin.rs

+#[cfg(not(feature = "downcast"))]
+#[doc(hidden)]
+pub trait Downcast {}
+
+#[cfg(not(feature = "downcast"))]
+impl<T: ?Sized> Downcast for T {}


downcast-rs isn't compatible with portablie-atomic (though it could be with a PR I believe!), so I've included a little dummy trait so the Plugin: Downcast bound can remain.

bushrat011899 · 2024-12-18T00:21:55Z

crates/bevy_app/src/app.rs

+#[cfg(feature = "trace")]
+use tracing::info_span;


As with bevy_ecs, I'm flattening our relationship with bevy_utils::tracing and also relying on log for non-span logging. It's already been mentioned that we should probably move things like log and tracing into workspace dependencies, but I'm just maintaining status quo for now.

bushrat011899 · 2024-12-18T00:22:49Z

crates/bevy_app/src/lib.rs

 mod sub_app;
-#[cfg(not(target_arch = "wasm32"))]
+#[cfg(all(not(target_arch = "wasm32"), feature = "std"))]
 mod terminal_ctrl_c_handler;


Can't use Control-C in the terminal if your platform doesn't have a terminal...or a keyboard...

bushrat011899 · 2024-12-18T00:24:20Z

crates/bevy_app/src/sub_app.rs


    /// See [`App::get_added_plugins`].
+    #[cfg(feature = "downcast")]
    pub fn get_added_plugins<T>(&self) -> Vec<&T>


This is the only real consequence of losing downcast-rs support on certain no_std targets (not all!). I would like to bring feature parity regardless, but it is fairly minor IMO.

crates/bevy_app/src/sub_app.rs

alice-i-cecile · 2024-12-18T00:35:05Z

No serious problems here; let me know when this is ready.

Co-Authored-By: Alice Cecile <[email protected]>

# Objective - Contributes to bevyengine#15460 ## Solution - Added the following features: - `std` (default) - `bevy_tasks` (default) - `downcast ` (default) - `portable-atomic` - `critical-section` - `downcast` and `bevy_tasks` are now optional dependencies for `bevy_app`. ## Testing - CI - Personal UEFI and Raspberry Pi Pico demo applications compile and run against this branch ## Draft Release Notes Bevy's application framework now supports `no_std` platforms. Following up on `bevy_ecs` gaining `no_std` support, `bevy_app` extends the functionality available on these targets to include the powerful `App` and `Plugin` abstractions. With this, library authors now have the option of making their plugins `no_std` compatible, or even offering plugins specifically to improve Bevy on certain embedded platforms! To start making a `no_std` compatible plugin, simply disable default features when including `bevy_app`: ```toml [dependencies] bevy_app = { version = "0.16", default-features = false } ``` We encourage library authors to do this anyway, as it can also help with compile times and binary size on all platforms. Keep an eye out for future `no_std` updates as we continue to improve the parity between `std` and `no_std`. We look forward to seeing what kinds of applications are now possible with Bevy! ## Notes - `downcast-rs` is optional as it isn't compatible with `portable-atomic`. I will investigate making a PR upstream to add support for this functionality, as it should be very straightforward. - In line with the `bevy_ecs` no-std-ification, I've added documentation to all features, and grouped them as well. - ~~Creating this PR in draft while CI runs and so I can polish before review.~~ --------- Co-authored-by: Alice Cecile <[email protected]>

alice-i-cecile · 2025-03-25T20:07:34Z

Thank you to everyone involved with the authoring or reviewing of this PR! This work is relatively important and needs release notes! Head over to bevyengine/bevy-website#1977 if you'd like to help out.

Initial Commit

3472656

bushrat011899 mentioned this pull request Dec 17, 2024

Tracking Issue: MVP no_std Bevy #15460

Closed

bushrat011899 commented Dec 18, 2024

View reviewed changes

bushrat011899 added 2 commits December 18, 2024 11:26

Added missing documentation

dda4dc2

Merge remote-tracking branch 'upstream/main' into NoSTDBevyApp

5200f5b

bushrat011899 marked this pull request as ready for review December 18, 2024 00:27

alice-i-cecile added this to the 0.16 milestone Dec 18, 2024

alice-i-cecile reviewed Dec 18, 2024

View reviewed changes

crates/bevy_app/src/sub_app.rs Show resolved Hide resolved

bushrat011899 mentioned this pull request Dec 18, 2024

Reorganise Platform Support Dependencies #16877

Closed

bushrat011899 and others added 2 commits December 18, 2024 11:38

TODO For downcast_rs

eb8fc79

Co-Authored-By: Alice Cecile <[email protected]>

Added link to downcast-rs PR

eab7df6

BenjaminBrienen approved these changes Dec 18, 2024

View reviewed changes

bushrat011899 added 2 commits December 19, 2024 07:33

Merge remote-tracking branch 'upstream/main' into NoSTDBevyApp

2589853

Merge remote-tracking branch 'upstream/main' into NoSTDBevyApp

87fbca8

heydocode approved these changes Dec 18, 2024

View reviewed changes

bushrat011899 added S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it and removed S-Waiting-on-Author The author needs to make changes or address concerns before this can be merged labels Dec 18, 2024

alice-i-cecile added this pull request to the merge queue Dec 18, 2024

Merged via the queue into bevyengine:main with commit f45e78e Dec 18, 2024

TimJentzsch added the O-Embedded Weird hardware and no_std platforms label Dec 31, 2024

alice-i-cecile mentioned this pull request Mar 25, 2025

Write release notes for PR #16874: Add no_std support to bevy_app bevyengine/bevy-website#1977

Closed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Add `no_std` support to `bevy_app`#16874

Add `no_std` support to `bevy_app`#16874
alice-i-cecile merged 7 commits intobevyengine:mainfrom
bushrat011899:NoSTDBevyApp

bushrat011899 commented Dec 17, 2024 •

edited

Loading

Uh oh!

bushrat011899 Dec 18, 2024

Uh oh!

bushrat011899 Dec 18, 2024

Uh oh!

bushrat011899 Dec 18, 2024

Uh oh!

bushrat011899 Dec 18, 2024

Uh oh!

alice-i-cecile Dec 18, 2024

Uh oh!

bushrat011899 Dec 18, 2024

Uh oh!

bushrat011899 Dec 18, 2024

Uh oh!

bushrat011899 Dec 18, 2024

Uh oh!

bushrat011899 Dec 18, 2024

Uh oh!

Uh oh!

alice-i-cecile commented Dec 18, 2024

Uh oh!

alice-i-cecile commented Mar 25, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

		#[cfg(any(target_arch = "wasm32", feature = "std"))]
		use bevy_utils::Instant;

Uh oh!

Conversation

bushrat011899 commented Dec 17, 2024 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Objective

Solution

Testing

Draft Release Notes

Notes

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

alice-i-cecile commented Dec 18, 2024

Uh oh!

alice-i-cecile commented Mar 25, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

bushrat011899 commented Dec 17, 2024 •

edited

Loading