1. https://github.com/bevyengine/bevy/pull/4775

Parallelized transform propagation! Great example of targeted, profile-guided optimization based on the challenges seen in practice.

Initially testing looks good. Seeing modest performance improvements on large, scenes, and nothing noticeable on small scenes. Needs to be rebased to provide a fair comparison due to our other changes, but even still it's faster!

Gut feel on change detection worked out, but didn't seem worth it in more realistic cases.

bors r+

2. https://github.com/bevyengine/bevy/pull/5214

#RustLang's `ExactSizeIterator` trait didn't work how we expected. The size hint is for "remaining items", not total items.

That's been better documented upstream now (thanks!) https://github.com/rust-lang/rust/issues/98721.

Now, this PR fixes our mistake.

bors r+

3. https://github.com/bevyengine/bevy/pull/6524

When we were panicking on a thread, it was leaking upwards, and breaking other threads. This resulted in some *really* frustrating flaky tests in CI with #[should_panic] annotations.

It was likely even more damaging in actual use cases, as it prevents graceful failure.

This PR handles this more gracefully, by catching the unwind (and just dropping the error). Annoying that there's a small perf regression, but correct code is better than fast code.

bors r+

4. https://github.com/bevyengine/bevy/pull/6535

Ah, flexbox, my old nemesis. `Margin::Auto` is used consistently throughout our examples as a way to center items, but it's not very robust and is an old pre-flexbox #css hack.

Instead, actually set the alignment and justification of your parent.

Annoying that this is more verbose, but this is much clearer for beginners to learn from (and tweak). Time to rebase https://github.com/bevyengine/bevy/pull/5513...

bors r+

5. https://github.com/bevyengine/bevy/pull/6547

Another PR by James, another sizable performance win. This one splits apart our change detection ticks (u32s used to track what's been modified) into added / changed, rather than a joint struct.

This means that in the tight tight loops, we're iterating over less data, and get better cache efficiency. Huge wins for small components mutably iterated.

bors r+

6. https://github.com/bevyengine/bevy/pull/6664

Expose some more functionality from winit: passing cursor input through to the covered app.

With this + transparent windows I think that we're well overdue for Bonsai Buddy: Bevy Edition.

bors r+

7. https://github.com/bevyengine/bevy/pull/6672

Create a box from two corners! Perfectly useful. I agree with James's nit, but totally not worth blocking the PR on.

bors r+

8. https://github.com/bevyengine/bevy/pull/6692

Another helper method for Quaternion rotation! Should be useful when working with characters.

bors r+

9. https://github.com/bevyengine/bevy/pull/6676

Track the changed frames in CorePlugin, not RenderingPlugin, to be nicer to custom renderers, turn-based games and more. I'll actually use this myself in https://github.com/Leafwing-Studios/leafwing_input_playback

bors r+