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Updated docs for ShouldRun (#1987)

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The documentation for `ShouldRun` doesn't completely explain what each of the variants you can return does. For instance, it isn't very clear that looping systems aren't executed again until after all the systems in a stage have had a chance to run.

This PR adds to the documentation for `ShouldRun`, and hopefully clarifies what is happening during a stage's execution when run criteria are checked and systems are being executed.
This commit is contained in:
TehPers 2021-04-23 18:38:18 +00:00
parent 0a587ac3b5
commit d653ad2bda
1 changed files with 28 additions and 4 deletions
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32
crates/bevy_ecs/src/schedule/run_criteria.rs
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@ -8,15 +8,39 @@ use crate::{
};
use std::borrow::Cow;
/// Determines whether a system should be executed or not, and how many times it should be ran each
/// time the stage is executed.
///
/// A stage will loop over its run criteria and systems until no more systems need to be executed
/// and no more run criteria need to be checked.
/// - Any systems with run criteria that returns [`Yes`] will be ran exactly one more time during
/// the stage's execution that tick.
/// - Any systems with run criteria that returns [`No`] are not ran for the rest of the stage's
/// execution that tick.
/// - Any systems with run criteria that returns [`YesAndCheckAgain`] will be ran during this
/// iteration of the loop. After all the systems that need to run are ran, that criteria will be
/// checked again.
/// - Any systems with run criteria that returns [`NoAndCheckAgain`] will not be ran during this
/// iteration of the loop. After all the systems that need to run are ran, that criteria will be
/// checked again.
///
/// [`Yes`]: ShouldRun::Yes
/// [`No`]: ShouldRun::No
/// [`YesAndCheckAgain`]: ShouldRun::YesAndCheckAgain
/// [`NoAndCheckAgain`]: ShouldRun::NoAndCheckAgain
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ShouldRun {
/// Yes, the system should run.
/// Yes, the system should run one more time this tick.
Yes,
/// No, the system should not run.
/// No, the system should not run for the rest of this tick.
No,
/// Yes, the system should run, and afterwards the criteria should be checked again.
/// Yes, the system should run, and after all systems in this stage have run, the criteria
/// should be checked again. This will cause the stage to loop over the remaining systems and
/// criteria this tick until they no longer need to be checked.
YesAndCheckAgain,
/// No, the system should not run right now, but the criteria should be checked again later.
/// No, the system should not run right now, but after all systems in this stage have run, the
/// criteria should be checked again. This will cause the stage to loop over the remaining
/// systems and criteria this tick until they no longer need to be checked.
NoAndCheckAgain,
}