feat: static System priority (#3207)

Closes #3102

## Changes:

- Refactored `System.priority` to be static
- Updated `priority` in all systems
- Updated priority sort in `SystemManager`

CHANGELOG.md

@@ -7,6 +7,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Breaking Changes
 
+- `System.priority` is refactored to be static.
 - `ex.Timer` now only takes the option bag constructor
 - `PreDrawEvent`, `PostDrawEvent`, `PreTransformDrawEvent`, `PostTransformDrawEvent`, `PreUpdateEvent`, `PostUpdateEvent` now use `elapsedMs` instead of `delta` for the elapsed milliseconds between the last frame.460696
 - `Trigger` API has been slightly changed:

src/engine/Actions/ActionsSystem.ts

@@ -3,8 +3,9 @@ import { System, SystemType } from '../EntityComponentSystem/System';
 import { ActionsComponent } from './ActionsComponent';
 
 export class ActionsSystem extends System {
+  static priority = SystemPriority.Higher;
+
   systemType = SystemType.Update;
-  priority = SystemPriority.Higher;
   private _actions: ActionsComponent[] = [];
   query: Query<typeof ActionsComponent>;
 

src/engine/Collision/CollisionSystem.ts

@@ -21,8 +21,9 @@ import { SeparatingAxis } from './Colliders/SeparatingAxis';
 import { MotionSystem } from './MotionSystem';
 import { Pair } from './Detection/Pair';
 export class CollisionSystem extends System {
+  static priority = SystemPriority.Higher;
+
   public systemType = SystemType.Update;
-  public priority = SystemPriority.Higher;
   public query: Query<ComponentCtor<TransformComponent> | ComponentCtor<MotionComponent> | ComponentCtor<ColliderComponent>>;
 
   private _engine: Engine;

src/engine/Collision/MotionSystem.ts

@@ -8,8 +8,9 @@ import { EulerIntegrator } from './Integrator';
 import { PhysicsWorld } from './PhysicsWorld';
 
 export class MotionSystem extends System {
+  static priority = SystemPriority.Higher;
+
   public systemType = SystemType.Update;
-  public priority = SystemPriority.Higher;
   private _physicsConfigDirty = false;
   query: Query<typeof TransformComponent | typeof MotionComponent>;
   constructor(

src/engine/Debug/DebugSystem.ts

@@ -18,8 +18,9 @@ import { CoordPlane } from '../Math/coord-plane';
 import { Debug } from '../Graphics/Debug';
 
 export class DebugSystem extends System {
+  static priority = SystemPriority.Lowest;
+
   public readonly systemType = SystemType.Draw;
-  public priority = SystemPriority.Lowest;
   private _graphicsContext: ExcaliburGraphicsContext;
   private _collisionSystem: CollisionSystem;
   private _camera: Camera;

src/engine/EntityComponentSystem/System.ts

@@ -42,7 +42,7 @@ export abstract class System {
    * For a system to execute before all other a lower priority value (-1 for example) must be set.
    * For a system to execute after all other a higher priority value (10 for example) must be set.
    */
-  public priority: number = SystemPriority.Average;
+  public static priority: number = SystemPriority.Average;
 
   /**
    * Optionally specify an initialize handler

src/engine/EntityComponentSystem/SystemManager.ts

@@ -47,7 +47,7 @@ export class SystemManager {
     }
 
     this.systems.push(system);
-    this.systems.sort((a, b) => a.priority - b.priority);
+    this.systems.sort((a, b) => (a.constructor as typeof System).priority - (b.constructor as typeof System).priority);
     // If systems are added and the manager has already been init'd
     // then immediately init the system
     if (this.initialized && system.initialize) {

src/engine/Graphics/GraphicsSystem.ts

@@ -18,8 +18,9 @@ import { blendTransform } from './TransformInterpolation';
 import { Graphic } from './Graphic';
 
 export class GraphicsSystem extends System {
+  static priority = SystemPriority.Average;
+
   public readonly systemType = SystemType.Draw;
-  public priority = SystemPriority.Average;
   private _token = 0;
   // Set in the initialize
   private _graphicsContext!: ExcaliburGraphicsContext;

src/engine/Graphics/OffscreenSystem.ts

@@ -12,8 +12,9 @@ import { BoundingBox } from '../Collision/BoundingBox';
 import { Query, SystemPriority, World } from '../EntityComponentSystem';
 
 export class OffscreenSystem extends System {
+  static priority: number = SystemPriority.Higher;
+
   public systemType = SystemType.Draw;
-  priority: number = SystemPriority.Higher;
   private _camera!: Camera;
   private _screen!: Screen;
   private _worldBounds!: BoundingBox;

src/engine/Input/PointerSystem.ts

@@ -16,8 +16,9 @@ import { SparseHashGrid } from '../Collision/Detection/SparseHashGrid';
  * the {@apilink Collider}'s shape for pointer events.
  */
 export class PointerSystem extends System {
+  static priority = SystemPriority.Higher;
+
   public readonly systemType = SystemType.Update;
-  public priority = SystemPriority.Higher;
 
   private _engine: Engine;
   private _receivers: PointerEventReceiver[];

src/engine/TileMap/IsometricEntitySystem.ts

@@ -4,8 +4,9 @@ import { IsometricEntityComponent } from './IsometricEntityComponent';
 import { Query, SystemPriority, World } from '../EntityComponentSystem';
 
 export class IsometricEntitySystem extends System {
+  static priority: number = SystemPriority.Lower;
+
   public readonly systemType = SystemType.Update;
-  priority: number = SystemPriority.Lower;
   query: Query<typeof TransformComponent | typeof IsometricEntityComponent>;
   constructor(public world: World) {
     super();

src/spec/SystemManagerSpec.ts

@@ -5,11 +5,45 @@ class FakeComponentA extends ex.Component {}
 class FakeComponentB extends ex.Component {}
 class FakeComponentC extends ex.Component {}
 
-class FakeSystem extends ex.System {
+class FakeSystemPriority1 extends ex.System {
+  static priority = 1;
+  query: ex.Query<ex.ComponentCtor<ex.Component>>;
+  constructor(
+    public world: ex.World,
+    public name: string,
+    public types: ex.ComponentCtor[],
+    public systemType: ex.SystemType
+  ) {
+    super();
+    this.query = this.world.query(types);
+  }
+  update(elapsedMs: number): void {
+    // fake
+  }
+}
+
+class FakeSystemPriority2 extends ex.System {
+  static priority = 2;
+  query: ex.Query<ex.ComponentCtor<ex.Component>>;
+  constructor(
+    public world: ex.World,
+    public name: string,
+    public types: ex.ComponentCtor[],
+    public systemType: ex.SystemType
+  ) {
+    super();
+    this.query = this.world.query(types);
+  }
+  update(elapsedMs: number): void {
+    // fake
+  }
+}
+
+class FakeSystemPriority3 extends ex.System {
+  static priority = 3;
   query: ex.Query<ex.ComponentCtor<ex.Component>>;
   constructor(
     public world: ex.World,
-    public priority: number,
     public name: string,
     public types: ex.ComponentCtor[],
     public systemType: ex.SystemType
@@ -36,11 +70,11 @@ describe('A SystemManager', () => {
     const sm = world.systemManager;
 
     // Lower priority
-    const s3 = new FakeSystem(world, 2, 'System3', [FakeComponentC], SystemType.Update);
+    const s3 = new FakeSystemPriority2(world, 'System3', [FakeComponentC], SystemType.Update);
     sm.addSystem(s3);
     // Systems of equal priority should preserve order
-    const s1 = new FakeSystem(world, 1, 'System1', [FakeComponentA], SystemType.Update);
-    const s2 = new FakeSystem(world, 1, 'System2', [FakeComponentC, FakeComponentB], SystemType.Update);
+    const s1 = new FakeSystemPriority1(world, 'System1', [FakeComponentA], SystemType.Update);
+    const s2 = new FakeSystemPriority1(world, 'System2', [FakeComponentC, FakeComponentB], SystemType.Update);
     sm.addSystem(s1);
     sm.addSystem(s2);
 
@@ -52,11 +86,11 @@ describe('A SystemManager', () => {
     const sm = world.systemManager;
 
     // Lower priority
-    const s3 = new FakeSystem(world, 2, 'System3', [FakeComponentC], SystemType.Update);
+    const s3 = new FakeSystemPriority2(world, 'System3', [FakeComponentC], SystemType.Update);
     sm.addSystem(s3);
     // Systems of equal priority should preserve order
-    const s1 = new FakeSystem(world, 1, 'System1', [FakeComponentA], SystemType.Update);
-    const s2 = new FakeSystem(world, 1, 'System2', [FakeComponentC, FakeComponentB], SystemType.Update);
+    const s1 = new FakeSystemPriority1(world, 'System1', [FakeComponentA], SystemType.Update);
+    const s2 = new FakeSystemPriority1(world, 'System2', [FakeComponentC, FakeComponentB], SystemType.Update);
     sm.addSystem(s1);
     sm.addSystem(s2);
 
@@ -69,7 +103,7 @@ describe('A SystemManager', () => {
   it('can update systems', () => {
     const world = new ex.World(null);
     const sm = world.systemManager;
-    const system = new FakeSystem(world, 2, 'System3', [FakeComponentC], SystemType.Update);
+    const system = new FakeSystemPriority2(world, 'System3', [FakeComponentC], SystemType.Update);
     system.preupdate = () => {}; // eslint-disable-line @typescript-eslint/no-empty-function
     system.postupdate = () => {}; // eslint-disable-line @typescript-eslint/no-empty-function
     spyOn(system, 'preupdate');
@@ -87,7 +121,7 @@ describe('A SystemManager', () => {
     const sm = world.systemManager;
     const qm = world.queryManager;
     const em = world.entityManager;
-    const system = new FakeSystem(world, 2, 'System3', [FakeComponentA, FakeComponentC], SystemType.Update);
+    const system = new FakeSystemPriority2(world, 'System3', [FakeComponentA, FakeComponentC], SystemType.Update);
     spyOn(system, 'update').and.callThrough();
     sm.addSystem(system);
 
@@ -119,10 +153,10 @@ describe('A SystemManager', () => {
     const sm = world.systemManager;
     const qm = world.queryManager;
     const em = world.entityManager;
-    const system1 = new FakeSystem(world, 2, 'System1', [FakeComponentA, FakeComponentC], SystemType.Update);
+    const system1 = new FakeSystemPriority2(world, 'System1', [FakeComponentA, FakeComponentC], SystemType.Update);
     spyOn(system1, 'update').and.callThrough();
     sm.addSystem(system1);
-    const system2 = new FakeSystem(world, 2, 'System1', [FakeComponentA, FakeComponentC], SystemType.Draw);
+    const system2 = new FakeSystemPriority2(world, 'System1', [FakeComponentA, FakeComponentC], SystemType.Draw);
     spyOn(system2, 'update').and.callThrough();
     sm.addSystem(system2);
 
@@ -136,7 +170,7 @@ describe('A SystemManager', () => {
     const world = new ex.World(null);
     const sm = world.systemManager;
     expect(() => {
-      sm.addSystem(new FakeSystem(world, 0, 'ErrorSystem', [], SystemType.Update));
+      sm.addSystem(new FakeSystemPriority1(world, 'ErrorSystem', [], SystemType.Update));
     }).toThrow(new Error('Cannot create query without components'));
   });
 });