Alternative to EventReader/Writer?

[remote knot]

For inter-system communication there seems to be only EventReader/Writer..problem is they can't be trusted when systems are running in different threads. How do people handle this problem in general?

[outer sphinx]

problem is they can't be trusted when systems are running in different threads. How do people handle this problem in general?
They can be trusted though? Are you ordering your systems?

[remote knot]

I have a system that runs the ui (egui) it runs at an unspecifed fps, then another running the gamelogic at 60fps..the 60fps doesnt receive the messages always from the gui

[outer sphinx]

Oh right

That's because events are double-buffered

Not a problem with threads

But the events aren't persisting long enough

You could replace the cleanup logic added via .add_event with your own equivalent

[remote knot]

Since there are so many ways to to schedule your systems, will the event system ever be truly useful?

"You could replace the cleanup logic added via .add_event with your own equivalent"

Not sure what you mean here

[outer sphinx]

https://github.com/bevyengine/rfcs/pull/32 This discusses an alternative architecture

https://github.com/bevyengine/bevy/blob/670c4c1852198bd1e23e10e532e879a5e1600c24/crates/bevy_app/src/app.rs#L589

[remote knot]

Yes ok..but nothing concrete now? I'd say the event buffer (or whatever it is) should simply be cleared wh all systems ran..though that probably causes other problems

[outer sphinx]

So, you can see how events work right now

They're just stored in a resource

And you have a cleanup system that runs every frame

But that doesn't work if you need events from older than two frames ago

Which can happen when you're using a fixed timestep

Instead, you could make your own system

And an extension method on App

Which runs the cleanup logic after every fixed timestep has elapsed

Which will avoid this issue

[remote knot]

extension method on app? what is that?

[outer sphinx]

This pattern 🙂 https://rust-lang.github.io/rfcs/0445-extension-trait-conventions.html

To add more methods to foreign types

[remote knot]

OK thought that wasnt possible..I tried that but got errors

Pretty neat

This page describes the problem it seems https://bevy-cheatbook.github.io/patterns/manual-event-clear.html

[outer sphinx]

Yes 🙂

Proper writeup for you: https://github.com/bevyengine/bevy/issues/7691

[remote knot]

Thanks

I dont see alternatives to fixed time step, since the game runs at 300fps on my laptop screen, and 60 on my stationary screen. Cant have game run differently depending on screen

[outer sphinx]

I would consider using bevy_framepace for now

[remote knot]

Ah ok that makes it possible just to run everything like a completely barebones bevy app..thanks for the tip! should take care of the event problem as well.

[outer sphinx]

Yep! It's a lovely crate

[foggy wolf]

an alternative is to use a channel https://docs.rs/crossbeam-channel/latest/crossbeam_channel/ you can just store it in a Resource