Standardize on dt in update methods (#679)

* Standardize on dt in update methods

* Update changelog entry

* Update CHANGELOG.md

Co-authored-by: Jochum van der Ploeg <jochum@vdploeg.net>

Co-authored-by: Jochum van der Ploeg <jochum@vdploeg.net>

CHANGELOG.md

@@ -22,6 +22,7 @@
  - Add utility methods to the Anchor class to make it more "enum like"
  - Enable user-defined anchors
  - Added `toImage` method for the `Sprite` class
+ - Uniform use of `dt` instead of `t` in all update methods
  - Add more optional arguments for unified constructors of components
 
 ## 1.0.0-rc6

doc/examples/nine_tile_box/lib/main.dart

@@ -31,5 +31,5 @@ class MyGame extends Game {
   }
 
   @override
-  void update(double t) {}
+  void update(double dt) {}
 }

example/lib/main.dart

@@ -37,9 +37,9 @@ class Square extends PositionComponent with HasGameRef<MyGame> {
   }
 
   @override
-  void update(double t) {
+  void update(double dt) {
-    super.update(t);
+    super.update(dt);
-    angle += SPEED * t;
+    angle += SPEED * dt;
     angle %= 2 * math.pi;
   }
 

lib/src/components/joystick/joystick_directional.dart

@@ -110,8 +110,8 @@ class JoystickDirectional extends BaseComponent with Draggable, HasGameRef {
   }
 
   @override
-  void update(double t) {
+  void update(double dt) {
-    super.update(t);
+    super.update(dt);
     if (_dragging) {
       final delta = _dragPosition - _backgroundRect.center.toVector2();
       final radAngle = atan2(delta.y, delta.x);

lib/src/components/mixins/single_child_particle.dart

@@ -41,10 +41,10 @@ mixin SingleChildParticle on Particle {
   }
 
   @override
-  void update(double t) {
+  void update(double dt) {
     assert(child != null);
 
-    super.update(t);
+    super.update(dt);
-    child.update(t);
+    child.update(dt);
   }
 }

lib/src/components/parallax_component.dart

@@ -62,9 +62,9 @@ class ParallaxComponent extends PositionComponent {
   }
 
   @override
-  void update(double t) {
+  void update(double dt) {
-    super.update(t);
+    super.update(dt);
-    parallax?.update(t);
+    parallax?.update(dt);
   }
 
   @mustCallSuper

lib/src/components/sprite_animation_component.dart

@@ -69,8 +69,8 @@ class SpriteAnimationComponent extends PositionComponent {
   }
 
   @override
-  void update(double t) {
+  void update(double dt) {
-    super.update(t);
+    super.update(dt);
-    animation?.update(t);
+    animation?.update(dt);
   }
 }

lib/src/game/base_game.dart

@@ -136,7 +136,7 @@ class BaseGame extends Game with FPSCounter {
   /// You can override it further to add more custom behavior.
   @override
   @mustCallSuper
-  void update(double t) {
+  void update(double dt) {
     _removeLater.addAll(components.where((c) => c.shouldRemove));
     _removeLater.forEach((c) {
       c.onRemove();
@@ -155,7 +155,7 @@ class BaseGame extends Game with FPSCounter {
       addNow.forEach((component) => component.onMount());
     }
 
-    components.forEach((c) => c.update(t));
+    components.forEach((c) => c.update(dt));
   }
 
   /// This implementation of resize passes the resize call along to every component in the list, enabling each one to make their decisions as how to handle the resize.

lib/src/game/game.dart

@@ -57,10 +57,10 @@ abstract class Game {
   /// It cannot be changed at runtime, because the game widget does not get rebuild when this value changes.
   Color backgroundColor() => const Color(0xFF000000);
 
-  /// Implement this method to update the game state, given that a time [t] has passed.
+  /// Implement this method to update the game state, given the time [dt] that has passed since the last update.
   ///
-  /// Keep the updates as short as possible. [t] is in seconds, with microseconds precision.
+  /// Keep the updates as short as possible. [dt] is in seconds, with microseconds precision.
-  void update(double t);
+  void update(double dt);
 
   /// Implement this method to render the current game state in the [canvas].
   void render(Canvas canvas);

lib/src/parallax.dart

@@ -266,10 +266,10 @@ class Parallax {
     }
   }
 
-  void update(double t) {
+  void update(double dt) {
     layers.forEach((layer) {
       layer.update(
-        (baseVelocity.clone()..multiply(layer.velocityMultiplier)) * t,
+        (baseVelocity.clone()..multiply(layer.velocityMultiplier)) * dt,
       );
     });
   }

lib/src/particles/accelerated_particle.dart

@@ -38,10 +38,10 @@ class AcceleratedParticle extends CurvedParticle with SingleChildParticle {
   }
 
   @override
-  void update(double t) {
+  void update(double dt) {
-    speed += acceleration * t;
+    speed += acceleration * dt;
-    position += speed * t - (acceleration * t * t) / 2;
+    position += speed * dt - (acceleration * dt * dt) / 2;
 
-    super.update(t);
+    super.update(dt);
   }
 }