Making velocities and deltas have the game and global values (#769)

* Making velocities and deltas have the game and global values

* Re adding code metircs

* Re adding code metircs

* Update packages/flame/lib/src/gestures/events.dart

Co-authored-by: Luan Nico <luanpotter27@gmail.com>

* Renaming example variable

* fixing example

* Linting

Co-authored-by: Luan Nico <luanpotter27@gmail.com>

examples/lib/main.dart

@@ -3,6 +3,7 @@ import 'package:flame/flame.dart';
 import 'package:flutter/material.dart';
 
 import 'stories/animations/animations.dart';
+import 'stories/camera_and_viewport/camera_and_viewport.dart';
 import 'stories/collision_detection/collision_detection.dart';
 import 'stories/components/components.dart';
 import 'stories/controls/controls.dart';
@@ -29,6 +30,7 @@ void main() async {
   addSpritesStories(dashbook);
   addRenderingStories(dashbook);
   addUtilsStories(dashbook);
+  addCameraAndViewportStories(dashbook);
   addParallaxStories(dashbook);
 
   await _setupWidgetsExample();

examples/lib/stories/camera_and_viewport/camera_and_viewport.dart

@@ -0,0 +1,51 @@
+import 'package:dashbook/dashbook.dart';
+import 'package:flame/game.dart';
+
+import '../../commons/commons.dart';
+import 'follow_object.dart';
+import 'zoom.dart';
+
+void addCameraAndViewportStories(Dashbook dashbook) {
+  dashbook.storiesOf('Camera & Viewport')
+    ..add(
+      'Follow Object',
+      (context) {
+        return GameWidget(
+          game: CameraAndViewportGame(
+            viewportResolution: Vector2(
+              context.numberProperty('viewport width', 500),
+              context.numberProperty('viewport height', 500),
+            ),
+          ),
+        );
+      },
+      codeLink: baseLink('camera_and_viewport/follow_object.dart'),
+      /*
+         Text for instructions:
+
+         Move around with W, A, S, D and notice how the camera follows the white square
+         The blue squares can also be clicked to show how the coordinate system respect
+         The camera transformation
+      */
+    )
+    ..add(
+      'Zoom',
+      (context) {
+        return GameWidget(
+          game: ZoomGame(
+            viewportResolution: Vector2(
+              context.numberProperty('viewport width', 500),
+              context.numberProperty('viewport height', 500),
+            ),
+          ),
+        );
+      },
+      codeLink: baseLink('camera_and_viewport/zoom.dart'),
+      /*
+         Text for instructions:
+
+         On web: use scroll to zoom in and out
+         On mobile: use scale gesture to zoom in and out
+      */
+    );
+}

examples/lib/stories/camera_and_viewport/follow_object.dart

@@ -118,9 +118,15 @@ class CameraAndViewportGame extends BaseGame
     with KeyboardEvents, HasCollidables, HasTapableComponents {
   late MovableSquare square;
 
+  final Vector2 viewportResolution;
+
+  CameraAndViewportGame({
+    required this.viewportResolution,
+  });
+
   @override
   Future<void> onLoad() async {
-    viewport = FixedResolutionViewport(Vector2(500, 500));
+    viewport = FixedResolutionViewport(viewportResolution);
     add(Map());
 
     add(square = MovableSquare());

examples/lib/stories/camera_and_viewport/zoom.dart

@@ -0,0 +1,47 @@
+import 'package:flame/components.dart';
+import 'package:flame/game.dart';
+import 'package:flame/gestures.dart';
+
+class ZoomGame extends BaseGame with ScrollDetector, ScaleDetector {
+  final Vector2 viewportResolution;
+  late SpriteComponent flame;
+
+  Vector2? lastScale;
+
+  ZoomGame({
+    required this.viewportResolution,
+  });
+
+  @override
+  Future<void> onLoad() async {
+    final flameSprite = await loadSprite('flame.png');
+
+    viewport = FixedResolutionViewport(viewportResolution);
+
+    final flameSize = Vector2(149, 211);
+    add(
+      flame = SpriteComponent(
+        sprite: flameSprite,
+        size: flameSize,
+      )..anchor = Anchor.center,
+    );
+    camera.followComponent(flame);
+  }
+
+  static const zoomPerScrollUnit = 0.001;
+  @override
+  void onScroll(PointerScrollInfo event) {
+    camera.zoom += event.scrollDelta.game.y * zoomPerScrollUnit;
+  }
+
+  @override
+  void onScaleUpdate(ScaleUpdateInfo info) {
+    final scale = lastScale;
+    if (scale != null) {
+      final delta = info.scale.game - scale;
+      camera.zoom += delta.y;
+    }
+
+    lastScale = info.scale.game;
+  }
+}

examples/lib/stories/controls/scroll.dart

@@ -14,7 +14,7 @@ class ScrollGame extends BaseGame with ScrollDetector {
 
   @override
   void onScroll(PointerScrollInfo event) {
-    target = position + event.scrollDelta * 5;
+    target = position + event.scrollDelta.game * 5;
   }
 
   @override

examples/lib/stories/utils/utils.dart

@@ -2,7 +2,6 @@ import 'package:dashbook/dashbook.dart';
 import 'package:flame/game.dart';
 
 import '../../commons/commons.dart';
-import 'camera_and_viewport.dart';
 import 'nine_tile_box.dart';
 import 'particles.dart';
 import 'timer.dart';
@@ -29,10 +28,5 @@ void addUtilsStories(Dashbook dashbook) {
       'Particles',
       (_) => GameWidget(game: ParticlesGame()),
       codeLink: baseLink('utils/particles.dart'),
-    )
-    ..add(
-      'Camera & Viewport',
-      (_) => GameWidget(game: CameraAndViewportGame()),
-      codeLink: baseLink('utils/camera_and_viewport.dart'),
     );
 }

packages/flame/lib/src/gestures/events.dart

@@ -26,6 +26,23 @@ class EventPosition {
   EventPosition(this._game, this._localPosition, this._globalPosition);
 }
 
+/// [EventDelta] converts deltas based events to two different values (game and global).
+///
+/// [global]: this is the raw value received by the event without any scale applied to it; this is always the same as local because Flutter doesn't apply any scaling.
+/// [game]: the scalled value applied all the game transformations.
+class EventDelta {
+  final Game _game;
+  final Offset _delta;
+
+  /// Scaled value relative to the game transformations
+  late final Vector2 game = _game.scaleVector(_delta.toVector2());
+
+  /// Raw value relative to the game transformations
+  late final Vector2 global = _delta.toVector2();
+
+  EventDelta(this._game, this._delta);
+}
+
 /// BaseInfo is the base class for Flame's input events.
 /// This base class just wraps Flutter's [raw] attribute.
 abstract class BaseInfo<T> {
@@ -104,8 +121,7 @@ class ForcePressInfo extends PositionInfo<ForcePressDetails> {
 }
 
 class PointerScrollInfo extends PositionInfo<PointerScrollEvent> {
-  late final Vector2 scrollDelta =
-      _game.unscaleVector(raw.scrollDelta.toVector2());
+  late final EventDelta scrollDelta = EventDelta(_game, raw.scrollDelta);
 
   PointerScrollInfo.fromDetails(
     Game game,
@@ -135,7 +151,7 @@ class DragStartInfo extends PositionInfo<DragStartDetails> {
 }
 
 class DragUpdateInfo extends PositionInfo<DragUpdateDetails> {
-  late final Vector2 delta = _game.unscaleVector(raw.delta.toVector2());
+  late final EventDelta delta = EventDelta(_game, raw.delta);
 
   DragUpdateInfo.fromDetails(
     Game game,
@@ -166,8 +182,9 @@ class ScaleStartInfo extends PositionInfo<ScaleStartDetails> {
 
 class ScaleEndInfo extends BaseInfo<ScaleEndDetails> {
   final Game _game;
-  late final Vector2 velocity =
-      _game.unscaleVector(raw.velocity.pixelsPerSecond.toVector2());
+  late final EventDelta velocity =
+      EventDelta(_game, raw.velocity.pixelsPerSecond);
+
   int get pointerCount => raw.pointerCount;
 
   ScaleEndInfo.fromDetails(
@@ -179,8 +196,10 @@ class ScaleEndInfo extends BaseInfo<ScaleEndDetails> {
 class ScaleUpdateInfo extends PositionInfo<ScaleUpdateDetails> {
   int get pointerCount => raw.pointerCount;
   double get rotation => raw.rotation;
-  late final Vector2 scale =
-      _game.unscaleVector(Vector2(raw.horizontalScale, raw.verticalScale));
+  late final EventDelta scale = EventDelta(
+    _game,
+    Offset(raw.horizontalScale, raw.verticalScale),
+  );
 
   ScaleUpdateInfo.fromDetails(
     Game game,