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Clarify Resource change detection behaviour in condition docs #19252

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Clarify Resource change detection behaviour in condition docs #19252

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8fbd75f
Clarify Resource change detection behaviour in condition docs
theotherphil May 17, 2025
6e54519
Merge branch 'main' into resourcechanged
theotherphil May 17, 2025
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28 changes: 10 additions & 18 deletions crates/bevy_ecs/src/schedule/condition.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -605,12 +605,11 @@ pub mod common_conditions {
}

/// A [`Condition`]-satisfying system that returns `true`
/// if the resource of the given type has had its value changed since the condition
/// was last checked.
/// if the resource of the given type has been added or mutably dereferenced
/// since the condition was last checked.
///
/// The value is considered changed when it is added. The first time this condition
/// is checked after the resource was added, it will return `true`.
/// Change detection behaves like this everywhere in Bevy.
/// **Note** that simply *mutably dereferencing* a resource is considered a change ([`DerefMut`](std::ops::DerefMut)).
/// Bevy does not compare resources to their previous values.
///
/// # Panics
///
Expand Down Expand Up @@ -659,14 +658,11 @@ pub mod common_conditions {
}

/// A [`Condition`]-satisfying system that returns `true`
/// if the resource of the given type has had its value changed since the condition
/// if the resource of the given type has been added or mutably dereferenced since the condition
/// was last checked.
///
/// The value is considered changed when it is added. The first time this condition
/// is checked after the resource was added, it will return `true`.
/// Change detection behaves like this everywhere in Bevy.
///
/// This run condition does not detect when the resource is removed.
/// **Note** that simply *mutably dereferencing* a resource is considered a change ([`DerefMut`](std::ops::DerefMut)).
/// Bevy does not compare resources to their previous values.
///
/// The condition will return `false` if the resource does not exist.
///
Expand Down Expand Up @@ -719,15 +715,11 @@ pub mod common_conditions {
}

/// A [`Condition`]-satisfying system that returns `true`
/// if the resource of the given type has had its value changed since the condition
/// if the resource of the given type has been added, removed or mutably dereferenced since the condition
/// was last checked.
///
/// The value is considered changed when it is added. The first time this condition
/// is checked after the resource was added, it will return `true`.
/// Change detection behaves like this everywhere in Bevy.
///
/// This run condition also detects removal. It will return `true` if the resource
/// has been removed since the run condition was last checked.
/// **Note** that simply *mutably dereferencing* a resource is considered a change ([`DerefMut`](std::ops::DerefMut)).
/// Bevy does not compare resources to their previous values.
///
/// The condition will return `false` if the resource does not exist.
///
Expand Down