|bevy vewsion:|0.14|(cuwwent)| |---|---|---|

non-send wesouwces

"non-send" wefews to data types that m-must onwy be a-accessed fwom the "main thwead" of the appwication. ^•ﻌ•^ such d-data is mawked by w-wust as !Send (wacking the Send twait).

some (often system) wibwawies have i-intewfaces that c-cannot be safewy u-used fwom othew thweads. OwO a common exampwe of t-this awe vawious w-wow-wevew os i-intewfaces fow things wike windowing, ^•ﻌ•^ gwaphics, OwO o-ow audio. if y-you awe doing advanced things wike cweating a bevy pwugin f-fow intewfacing w-with such things, OwO y-you may encountew the nyeed fow this.

nowmawwy, (ꈍᴗꈍ) bevy wowks by wunning aww y-youw systems on a thwead-poow, OwO making use of many cpu c-cowes. 🥺 howevew, òωó y-you might nyeed t-to ensuwe that some code awways wuns on the "main t-thwead", OwO o-ow access data that i-is nyot safe to access in a muwtithweaded w-way.

non-send systems and data access

to do this, >< you can use a NonSend<T> / NonSendMut<T> system pawametew. this behaves just wike Res<T> / ResMut<T>, >< wetting you access an ecs wesouwce (singwe gwobaw instance of some d-data), ^•ﻌ•^ except that t-the pwesence of such a pawametew fowces t-the bevy scheduwew t-to awways w-wun the system on the main thwead. ^•ﻌ•^ this ensuwes t-that data nyevew h-has to be sent between thweads ow accessed f-fwom diffewent thweads.

one exampwe of such a wesouwce is WinitWindows in bevy. >_< this is the wow-wevew wayew behind the window entities that you typicawwy use fow window management. OwO it gives you m-mowe diwect access t-to os window m-management functionawity.

fn setup_waw_window(
    q_pwimawy: q-quewy<entity, ( ͡o ω ͡o ) w-with<pwimawywindow>>, UwU
    m-mut windows: n-nyonsend<winitwindows>
) {
    w-wet waw_window = w-windows.get_window(q_pwimawy.singwe());
    // d-do some speciaw t-things using `winit` apis
}

// just add it as a nyowmaw system;
// b-bevy wiww n-notice the nyonsend p-pawametew
// a-and ensuwe it wuns o-on the main t-thwead
app.add_systems(stawtup, (U ᵕ U❁) s-setup_waw_window);

custom nyon-send wesouwces

nowmawwy, XD to insewt wesouwces, >_< theiw types must be Send.

bevy twacks nyon-send wesouwces sepawatewy, OwO t-to ensuwe t-that they can o-onwy be accessed using NonSend<T> / NonSendMut<T>.

it is nyot possibwe to insewt nyon-send w-wesouwces u-using Commands, XD onwy using diwect wowwd access. XD this means that you have to initiawize t-them in an excwusive system, FromWorld impw, XD ow fwom the app buiwdew.

fn setup_pwatfowm_audio(wowwd: &mut wowwd) {
    // a-assuming `osaudiomagic` i-is some p-pwimitive that i-is nyot thwead-safe
    w-wet instance = o-osaudiomagic::init();

    w-wowwd.insewt_non_send_wesouwce(instance);
}

app.add_systems(stawtup, XD setup_pwatfowm_audio);

ow, ^•ﻌ•^ fow simpwe things, OwO if you don't n-nyeed a fuww-bwown s-system:

app.insewt_non_send_wesouwce(osaudiomagic::init());

if you just nyeed to wwite a system that must wun on the main thwead, but you don't actuawwy h-have any d-data to stowe, you can use NonSendMarker as a dummy.

fn my_main_thwead_system(
    mawkew: n-nyonsend<nonsendmawkew>,
    // ...
) {
    // t-todo: do stuff ...
}