Engine

Engine

new Engine()

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This module manages the state of entities, components and systems. The heart of Entropy.

Extends

Members

(private) _entities :FastArray

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Array with entities. Array index corresponds to ID of an entity. First element is empty (equals 0), because entity IDs start from 1. Entity with id property equal 0 is officially not present in the system (it can be for example present in the pool or waiting for addition to system).

Type:
  • FastArray

(private) _entitiesCount :Number

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Current number of entities active.

Type:
  • Number

(private) _entitiesIdsPool :Pool

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When entity is removed, it's ID can be reused by new entities. This pool stores old IDs ready to reuse.

Type:
  • Pool

(private) _entitiesToAdd :FastArray

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Queue of entities ready to be added on next tick.

Type:
  • FastArray

(private) _entitiesToRemove :FastArray

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Queue of entities ready to be removed on next tick.

Type:
  • FastArray

(private) _events :Object

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Inherited From:

Object with registered event listeners. Keys are event names.

Type:
  • Object

(private) _isClearingScheduled :Boolean

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Indicates whether clearing is scheduled.

Type:
  • Boolean

(private) _modifiedEntities :FastArray

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List of modified entities.

When entity is modified it is added to this list. After each frame modifications are applied to every entity on the list.

Type:
  • FastArray

(private) _queries :Array

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Array of queries. Every query that was used is stored here and updated when engine state changes.

Type:
  • Array

(private) _systems :FastArray

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Systems that are processed every tick.

Type:
  • FastArray

(private) _systemsToAdd :FastArray

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Queue of systems ready to be added on next tick.

Type:
  • FastArray

(private) _systemsToRemove :FastArray

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Queue of systems ready to be removed on next tick.

Type:
  • FastArray

(private) _wasClearingPerformed :Boolean

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Indicates whether clearing was performed.

Type:
  • Boolean

Methods

addEntity(entity)

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Adds entity to adding queue. If entity is new (not recycled), adds event listener for modifications.

Parameters:
Name Type Description
entity Entity

entity to add

addSystem(system)

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Adds system to adding queue.

Parameters:
Name Type Description
system System

to add

clear()

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Schedules clearing. Clearing is done on next frame.

emit(event, …argopt)

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Inherited From:

Emits event. All listeners attached to this event name earlier will be called with arguments passed after event name.

Parameters:
Name Type Attributes Description
event String

event name
arg Any <optional>
<repeatable>

multiple arguments, that will be passed to listeners

getEntities(query) → {Object}

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Gets entities matching query criterions.

Parameters:
Name Type Description
query Query

query
Returns:

object with entities and length properties

Type
Object

off(event, fn)

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Inherited From:

Removes listener for event.

Example
const myHandler = (e) => {}
ee.on('myEvent', myHandler) // handler attached
ee.off('myEvent', myHandler) // handler detached
Parameters:
Name Type Description
event String

event name
fn function

listener function attached earlier

on(event, fn, onceopt)

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Inherited From:

Method used to register event listener.

Parameters:
Name Type Attributes Default Description
event String

event name
fn function

event listener
once Boolean <optional>
 false

if set to true, listener will be called once, then it will be unregistered

once(event, fn)

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Inherited From:

Same as EventEmitter#on, bu with implicit once parameter set to true.

Parameters:
Name Type Description
event String

event name
fn function

event listener

removeEntity(entity)

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Adds entity to removing queue.

Parameters:
Name Type Description
entity Entity

entity to remove

removeSystem(systemOrType)

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Adds system to removing queue.

Parameters:
Name Type Description
systemOrType String | System

system instance or system type to remove

startResponding()

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Inherited From:

Reenables disabled event emitter.

stopResponding()

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Inherited From:

Disables event emitter so it won't repond to any emitted events.

update(…args)

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Updates the engine:

  • updates systems (calls onUpdate method of every active system)
  • performs clearing, if scheduled
  • applies engine modifications (adding/removing entities/systems, updating queries)
Parameters:
Name Type Attributes Description
args Any <repeatable>

arguments passed to systems onUpdate methods
Fires:

Events

clear

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Engine was cleared.