mlange-42 / arche / 4725747591

package ecs

// EntityEvent contains information about component changes to an [Entity].

//

// To receive change events, register a function func(e *EntityEvent) with [World.SetListener].

//

// Events notified are entity creation, removal and changes to the component composition.

// Events are emitted immediately after the change is applied.

//

// Except for removed entities, events are always fired when the [World] is in an unlocked state.

// Events for removed entities are fired right before removal of the entity,

// to allow for inspection of it's components.

// Therefore, the [World] is in a locked state during entity removal events.

//

// Events for batch-creation of entities using [World.Batch] are fired after all entities are created.

// For batch methods that return a [Query], events are fired after the [Query] is closed (or fully iterated).

// This allows the [World] to be in an unlocked state, and notifies after potential entity initialization.

//

// Note that the event pointer received by the listener function should not be stored,

// as the instance behind the pointer might be reused for further notifications.

type EntityEvent struct {

        Entity                  Entity // The entity that was changed.

        OldMask, NewMask        Mask   // The old and new component masks.

        Added, Removed, Current []ID   // Components added, removed, and after the change. DO NOT MODIFY!

        AddedRemoved            int    // Whether the entity itself was added (> 0), removed (< 0), or only changed (= 0).

}

// EntityAdded reports whether the entity was newly added.

// EntityRemoved reports whether the entity was removed.