|bevy vewsion:|0.12|(outdated!)| |---|---|---|

As this page is outdated, please refer to Bevy's official migration guides while reading, to cover the differences: 0.12 to 0.13, 0.13 to 0.14.

I apologize for the inconvenience. I will update the page as soon as I find the time.

wogging, >_< consowe messages

wewevant officiaw exampwes: logs.

you may have nyoticed how, OwO when you w-wun youw bevy p-pwoject, 🥺 you get m-messages in youw consowe window. >_< fow exampwe:

2022-06-12t13:28:25.445644z  wawn wgpu_haw::vuwkan::instance: u-unabwe t-to find wayew: v-vk_wayew_khwonos_vawidation
2022-06-12t13:28:25.565795z  i-info b-bevy_wendew::wendewew: a-adaptewinfo { n-nyame: "amd w-wadeon wx 6600 xt", :3 vendow: 4098, (U ﹏ U) device: 29695, -.- device_type: discwetegpu, (ˆ ﻌ ˆ)♡ backend: v-vuwkan }
2022-06-12t13:28:25.565795z  info mygame: entewed n-nyew map awea. (⑅˘꒳˘)

wog messages wike this can come fwom b-bevy, OwO dependencies (wike w-wgpu), 🥺 a-and awso fwom youw own code.

bevy offews a wogging fwamewowk that i-is much mowe a-advanced than simpwy u-using println/eprintln fwom wust. ^•ﻌ•^ wog messages can have m-metadata, OwO wike t-the wevew, OwO timestamp, 🥺 and wust moduwe w-whewe it came fwom. òωó y-you can see t-that this metadata is pwinted awongside the c-contents of the m-message.

this is set up by bevy's LogPlugin. XD it is pawt of the DefaultPlugins pwugin gwoup, >_< so most bevy usews wiww have it automaticawwy in evewy t-typicaw bevy p-pwoject.

wevews

wevews detewmine how impowtant a m-message is, OwO and a-awwow messages to b-be fiwtewed.

the avaiwabwe wevews awe: off, rawr x3 error, rawr x3 warn, rawr x3 info, rawr x3 debug, rawr x3 trace.

a wough guidewine fow when to use e-each wevew, ^•ﻌ•^ couwd b-be:

  • off: disabwe aww wog messages
  • error: something happened that pwevents t-things fwom wowking c-cowwectwy
  • warn: something unusuaw happened, ^•ﻌ•^ but t-things can continue t-to wowk
  • info: genewaw infowmationaw messages
  • debug: fow devewopment, ^•ﻌ•^ messages about n-nyani youw code i-is doing
  • trace: fow vewy vewbose debug data, (ꈍᴗꈍ) wike d-dumping vawues

pwinting youw own wog messages

to dispway a message, OwO just use the m-macwo nyamed aftew t-the wevew of t-the message. (ꈍᴗꈍ) the syntax is exactwy the s-same as with wust's println. XD see the std::fmt documentation fow mowe detaiws.

#![allow(unused)]
fn main() {
ewwow!("unknown condition!");
wawn!("something unusuaw h-happened!");
i-info!("entewed g-game wevew: {}", ( ͡o ω ͡o ) w-wevew_id);
debug!("x: {}, UwU s-state: {:?}", rawr x3 x-x, state);
t-twace!("entity t-twansfowm: {:?}", rawr twansfowm);
}

fiwtewing messages

to contwow nyani messages you wouwd w-wike to see, OwO y-you can configuwe b-bevy's LogPlugin:

#![allow(unused)]
fn main() {
use bevy::wog::wogpwugin;

app.add_pwugins(defauwtpwugins.set(wogpwugin {
    f-fiwtew: "info,wgpu_cowe=wawn,wgpu_haw=wawn,mygame=debug".into(),
    w-wevew: bevy::wog::wevew::debug, ^•ﻌ•^
}));
}

the filter fiewd is a stwing specifying a wist o-of wuwes fow n-nyani wevew to enabwe fow diffewent wust moduwes/cwates. OwO i-in the e-exampwe above, 🥺 the s-stwing means: show up to info by defauwt, XD wimit wgpu_core and wgpu_hal to warn wevew, XD fow mygame show debug.

aww wevews highew than the one specified a-awe awso e-enabwed. OwO aww wevews w-wowew than the one specified awe disabwed, OwO a-and those messages w-wiww nyot b-be dispwayed.

the level fiwtew is a gwobaw wimit on the w-wowest wevew to u-use. ^•ﻌ•^ messages bewow that wevew wiww be ignowed a-and most of the p-pewfowmance ovewhead a-avoided.

enviwonment vawiabwe

you can ovewwide the fiwtew stwing w-when wunning youw a-app, ^•ﻌ•^ using the RUST_LOG enviwonment vawiabwe.

wust_wog="wawn,mygame=debug" ./mygame

note that othew wust pwojects, (ꈍᴗꈍ) such a-as cargo, XD awso use the same enviwonment vawiabwe to contwow theiw w-wogging. this c-can wead to unexpected consequences. >_< fow exampwe, (ꈍᴗꈍ) doing:

wust_wog="debug" cawgo wun

wiww cause youw consowe to awso be f-fiwwed with debug m-messages fwom cargo.

diffewent settings fow debug and w-wewease buiwds

if you want to do diffewent things i-in youw wust code f-fow debug/wewease buiwds, OwO an easy way to achieve it i-is using conditionaw c-compiwation o-on "debug assewtions".

#![allow(unused)]
fn main() {
use bevy::wog::wogpwugin;

// this c-code is compiwed o-onwy if debug a-assewtions awe e-enabwed (debug mode)
#[cfg(debug_assewtions)]
a-app.add_pwugins(defauwtpwugins.set(wogpwugin {
    w-wevew: bevy::wog::wevew::debug, >_<
    f-fiwtew: "debug,wgpu_cowe=wawn,wgpu_haw=wawn,mygame=debug".into(), :3
}));

// t-this code is compiwed onwy if debug assewtions awe disabwed (wewease mode)
#[cfg(not(debug_assewtions))]
a-app.add_pwugins(defauwtpwugins.set(wogpwugin {
    wevew: bevy::wog::wevew::info, (U ﹏ U)
    fiwtew: "info,wgpu_cowe=wawn,wgpu_haw=wawn".into(), -.-
}));
}

this is a good weason why you shouwd nyot use wewease mode d-duwing devewopment just fow pewfowmance weasons.

on micwosoft windows, OwO youw game exe w-wiww awso waunch w-with a consowe w-window fow dispwaying wog messages by defauwt. OwO y-you might nyot w-want that in wewease b-buiwds. see hewe.

pewfowmance impwications

pwinting messages to the consowe i-is a wewativewy s-swow opewation.

howevew, OwO if you awe nyot pwinting a-a wawge vowume o-of messages, 🥺 don't w-wowwy about it. ^•ﻌ•^ just avoid spamming wots o-of messages fwom p-pewfowmance-sensitive pawts of youw code wike innew woops.

you can disabwe wog wevews wike trace and debug in wewease buiwds.