refactor: Make GestureDetectorBuilder and detector/callback registering more resilient

packages/flame/lib/src/events/component_mixins/double_tap_callbacks.dart

@@ -10,6 +10,8 @@ import 'package:flame/events.dart';
 /// At present, flutter detects only one double-tap events simultaneously.
 /// This means that if you're double-tapping two [DoubleTapCallbacks] located
 /// far away from each other, only one callback will be fired (or none).
+///
+/// This callback uses [DoubleTapDispatcher] to route events.
 mixin DoubleTapCallbacks on Component {
   /// This triggers when the pointer stops contacting the device after the
   /// second tap.
@@ -25,11 +27,6 @@ mixin DoubleTapCallbacks on Component {
   @override
   void onMount() {
     super.onMount();
-    final game = findRootGame()!;
-    if (game.findByKey(const DoubleTapDispatcherKey()) == null) {
-      final dispatcher = DoubleTapDispatcher();
-      game.registerKey(const DoubleTapDispatcherKey(), dispatcher);
-      game.add(dispatcher);
-    }
+    DoubleTapDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/component_mixins/drag_callbacks.dart

@@ -10,6 +10,8 @@ import 'package:meta/meta.dart';
 /// the component.
 ///
 /// This mixin is the replacement of the Draggable mixin.
+///
+/// This callback uses [MultiDragDispatcher] to route events.
 mixin DragCallbacks on Component {
   bool _isDragged = false;
 
@@ -61,11 +63,6 @@ mixin DragCallbacks on Component {
   @mustCallSuper
   void onMount() {
     super.onMount();
-    final game = findRootGame()!;
-    if (game.findByKey(const MultiDragDispatcherKey()) == null) {
-      final dispatcher = MultiDragDispatcher();
-      game.registerKey(const MultiDragDispatcherKey(), dispatcher);
-      game.add(dispatcher);
-    }
+    MultiDragDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/component_mixins/hover_callbacks.dart

@@ -11,6 +11,8 @@ import 'package:meta/meta.dart';
 /// component.
 ///
 /// This mixin is the replacement of the Hoverable mixin.
+///
+/// This callback uses [PointerMoveDispatcher] to route events.
 mixin HoverCallbacks on Component implements PointerMoveCallbacks {
   bool _isHovered = false;
 
@@ -56,6 +58,6 @@ mixin HoverCallbacks on Component implements PointerMoveCallbacks {
   @mustCallSuper
   void onMount() {
     super.onMount();
-    PointerMoveCallbacks.onMountHandler(this);
+    PointerMoveDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/component_mixins/long_press_callbacks.dart

@@ -19,6 +19,8 @@ import 'package:flutter/foundation.dart';
 ///   long press.
 /// - [onLongPressEnd]: called when the pointer is lifted after a long press.
 /// - [onLongPressCancel]: called if the gesture is cancelled before completion.
+///
+/// This callback uses [LongPressDispatcher] to route events.
 mixin LongPressCallbacks on Component {
   bool _isLongPressing = false;
 
@@ -46,11 +48,6 @@ mixin LongPressCallbacks on Component {
   @mustCallSuper
   void onMount() {
     super.onMount();
-    final game = findRootGame()!;
-    if (game.findByKey(const LongPressDispatcherKey()) == null) {
-      final dispatcher = LongPressDispatcher();
-      game.registerKey(const LongPressDispatcherKey(), dispatcher);
-      game.add(dispatcher);
-    }
+    LongPressDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/component_mixins/pointer_move_callbacks.dart

@@ -4,6 +4,8 @@ import 'package:meta/meta.dart';
 
 /// This mixin can be added to a [Component] allowing it to receive
 /// pointer movement events.
+///
+/// This callback uses [PointerMoveDispatcher] to route events.
 mixin PointerMoveCallbacks on Component {
   void onPointerMove(PointerMoveEvent event) {}
 
@@ -13,16 +15,6 @@ mixin PointerMoveCallbacks on Component {
   @mustCallSuper
   void onMount() {
     super.onMount();
-    onMountHandler(this);
-  }
-
-  static void onMountHandler(PointerMoveCallbacks instance) {
-    final game = instance.findRootGame()!;
-    const key = MouseMoveDispatcherKey();
-    if (game.findByKey(key) == null) {
-      final dispatcher = PointerMoveDispatcher();
-      game.registerKey(key, dispatcher);
-      game.add(dispatcher);
-    }
+    PointerMoveDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/component_mixins/scale_callbacks.dart

@@ -3,6 +3,7 @@ import 'package:flame/events.dart';
 import 'package:flame/src/events/flame_game_mixins/scale_dispatcher.dart';
 import 'package:flutter/foundation.dart';
 
+/// This callback uses [ScaleDispatcher] to route events.
 mixin ScaleCallbacks on Component {
   bool _isScaling = false;
 
@@ -25,11 +26,6 @@ mixin ScaleCallbacks on Component {
   @mustCallSuper
   void onMount() {
     super.onMount();
-    final game = findRootGame()!;
-    if (game.findByKey(const ScaleDispatcherKey()) == null) {
-      final dispatcher = ScaleDispatcher();
-      game.registerKey(const ScaleDispatcherKey(), dispatcher);
-      game.add(dispatcher);
-    }
+    ScaleDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/component_mixins/scroll_callbacks.dart

@@ -5,23 +5,15 @@ import 'package:meta/meta.dart';
 
 /// This mixin can be added to a [Component] allowing it to receive
 /// pointer scroll (mouse wheel) events.
+///
+/// This callback uses [ScrollDispatcher] to route events.
 mixin ScrollCallbacks on Component {
   void onScroll(ScrollEvent event) {}
 
   @override
   @mustCallSuper
   void onMount() {
     super.onMount();
-    onMountHandler(this);
-  }
-
-  static void onMountHandler(ScrollCallbacks instance) {
-    final game = instance.findRootGame()!;
-    const key = ScrollDispatcherKey();
-    if (game.findByKey(key) == null) {
-      final dispatcher = ScrollDispatcher();
-      game.registerKey(key, dispatcher);
-      game.add(dispatcher);
-    }
+    ScrollDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/component_mixins/secondary_tap_callbacks.dart

@@ -11,6 +11,8 @@ import 'package:meta/meta.dart';
 ///
 /// Note that FlameGame _is_ a [Component] and does implement
 /// [containsLocalPoint]; so this can be used at the game level.
+///
+/// This callback uses [SecondaryTapDispatcher] to route events.
 mixin SecondaryTapCallbacks on Component {
   void onSecondaryTapDown(SecondaryTapDownEvent event) {}
   void onSecondaryTapUp(SecondaryTapUpEvent event) {}
@@ -20,11 +22,6 @@ mixin SecondaryTapCallbacks on Component {
   @mustCallSuper
   void onMount() {
     super.onMount();
-    final game = findRootGame()!;
-    if (game.findByKey(const SecondaryTapDispatcherKey()) == null) {
-      final dispatcher = SecondaryTapDispatcher();
-      game.registerKey(const SecondaryTapDispatcherKey(), dispatcher);
-      game.add(dispatcher);
-    }
+    SecondaryTapDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/component_mixins/tap_callbacks.dart

@@ -10,6 +10,8 @@ import 'package:meta/meta.dart';
 ///
 /// Note that FlameGame _is_ a [Component] and does implement
 /// [containsLocalPoint]; so this can be used at the game level.
+///
+/// This callback uses [MultiTapDispatcher] to route events.
 mixin TapCallbacks on Component {
   void onTapDown(TapDownEvent event) {}
   void onLongTapDown(TapDownEvent event) {}
@@ -20,11 +22,6 @@ mixin TapCallbacks on Component {
   @mustCallSuper
   void onMount() {
     super.onMount();
-    final game = findRootGame()!;
-    if (game.findByKey(const MultiTapDispatcherKey()) == null) {
-      final dispatcher = MultiTapDispatcher();
-      game.registerKey(const MultiTapDispatcherKey(), dispatcher);
-      game.add(dispatcher);
-    }
+    MultiTapDispatcher.addDispatcher(this);
   }
 }

packages/flame/lib/src/events/flame_game_mixins/dispatcher.dart

@@ -0,0 +1,23 @@
+import 'package:flame/components.dart';
+import 'package:flame/src/game/flame_game.dart';
+
+abstract class Dispatcher<G extends FlameGame> extends Component
+    with HasGameReference<G> {
+  static void addDispatcher<T extends Component>(
+    Component component,
+    ComponentKey key,
+    T Function() create,
+  ) {
+    final game = component.findRootGame()!;
+    if (game.findByKey(key) != null) {
+      return;
+    }
+    final dispatcher = create();
+    game.registerKey(key, dispatcher);
+    game.add(dispatcher);
+  }
+
+  static void removeDispatcher(FlameGame game, ComponentKey key) {
+    game.unregisterKey(key);
+  }
+}

packages/flame/lib/src/events/flame_game_mixins/double_tap_dispatcher.dart

@@ -1,6 +1,7 @@
 import 'package:flame/components.dart';
 import 'package:flame/events.dart';
 import 'package:flame/game.dart';
+import 'package:flame/src/events/flame_game_mixins/dispatcher.dart';
 import 'package:flutter/gestures.dart';
 
 class DoubleTapDispatcherKey implements ComponentKey {
@@ -18,7 +19,7 @@ class DoubleTapDispatcherKey implements ComponentKey {
 /// the component tree that is mixed with [DoubleTapCallbacks]. This will be
 /// attached to the [FlameGame] instance automatically whenever any
 /// [DoubleTapCallbacks] are mounted into the component tree.
-class DoubleTapDispatcher extends Component with HasGameReference<FlameGame> {
+class DoubleTapDispatcher extends Dispatcher<FlameGame> {
   final _components = <DoubleTapCallbacks>{};
 
   void _onDoubleTapDown(DoubleTapDownEvent event) {
@@ -44,9 +45,17 @@ class DoubleTapDispatcher extends Component with HasGameReference<FlameGame> {
     _components.clear();
   }
 
+  static void addDispatcher(Component component) {
+    Dispatcher.addDispatcher(
+      component,
+      const DoubleTapDispatcherKey(),
+      DoubleTapDispatcher.new,
+    );
+  }
+
   @override
   void onMount() {
-    game.gestureDetectors.add(
+    game.gestureDetectors.register<DoubleTapGestureRecognizer>(
       DoubleTapGestureRecognizer.new,
       (DoubleTapGestureRecognizer instance) {
         instance.onDoubleTapDown = (details) =>
@@ -60,7 +69,7 @@ class DoubleTapDispatcher extends Component with HasGameReference<FlameGame> {
 
   @override
   void onRemove() {
-    game.gestureDetectors.remove<DoubleTapGestureRecognizer>();
-    game.unregisterKey(const DoubleTapDispatcherKey());
+    game.gestureDetectors.unregister<DoubleTapGestureRecognizer>();
+    Dispatcher.removeDispatcher(game, const DoubleTapDispatcherKey());
   }
 }

packages/flame/lib/src/events/flame_game_mixins/long_press_dispatcher.dart

@@ -1,5 +1,6 @@
 import 'package:flame/components.dart';
 import 'package:flame/src/events/component_mixins/long_press_callbacks.dart';
+import 'package:flame/src/events/flame_game_mixins/dispatcher.dart';
 import 'package:flame/src/events/messages/long_press_cancel_event.dart';
 import 'package:flame/src/events/messages/long_press_end_event.dart';
 import 'package:flame/src/events/messages/long_press_move_update_event.dart';
@@ -13,12 +14,10 @@ import 'package:meta/meta.dart';
 /// that use the [LongPressCallbacks] mixin. It will be attached to the
 /// [FlameGame] instance automatically whenever any [LongPressCallbacks]
 /// components are mounted into the component tree.
-class LongPressDispatcher extends Component {
+class LongPressDispatcher extends Dispatcher<FlameGame> {
   /// Records all components currently being long-pressed, keyed by pointerId.
   final Set<TaggedComponent<LongPressCallbacks>> _records = {};
 
-  FlameGame get game => parent! as FlameGame;
-
   /// Monotonically increasing id assigned to each new long press gesture.
   int _nextPointerId = 0;
 
@@ -123,9 +122,17 @@ class LongPressDispatcher extends Component {
 
   //#endregion
 
+  static void addDispatcher(Component component) {
+    Dispatcher.addDispatcher(
+      component,
+      const LongPressDispatcherKey(),
+      LongPressDispatcher.new,
+    );
+  }
+
   @override
   void onMount() {
-    game.gestureDetectors.add<LongPressGestureRecognizer>(
+    game.gestureDetectors.register<LongPressGestureRecognizer>(
       LongPressGestureRecognizer.new,
       (LongPressGestureRecognizer instance) {
         instance
@@ -140,9 +147,8 @@ class LongPressDispatcher extends Component {
 
   @override
   void onRemove() {
-    game.gestureDetectors.remove<LongPressGestureRecognizer>();
-    game.unregisterKey(const LongPressDispatcherKey());
-    super.onRemove();
+    game.gestureDetectors.unregister<LongPressGestureRecognizer>();
+    Dispatcher.removeDispatcher(game, const LongPressDispatcherKey());
   }
 }
 

packages/flame/lib/src/events/flame_game_mixins/multi_drag_dispatcher.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:flame/components.dart';
 import 'package:flame/events.dart';
 import 'package:flame/src/events/flame_drag_adapter.dart';
+import 'package:flame/src/events/flame_game_mixins/dispatcher.dart';
 import 'package:flame/src/events/tagged_component.dart';
 import 'package:flame/src/game/flame_game.dart';
 import 'package:flame/src/game/game_render_box.dart';
@@ -24,7 +25,8 @@ class MultiDragDispatcherKey implements ComponentKey {
 /// [DragCallbacks] components in the component tree. It will be attached to
 /// the [FlameGame] instance automatically whenever any [DragCallbacks]
 /// components are mounted into the component tree.
-class MultiDragDispatcher extends Component implements MultiDragListener {
+class MultiDragDispatcher extends Dispatcher<FlameGame>
+    implements MultiDragListener {
   /// The record of all components currently being touched.
   final Set<TaggedComponent<DragCallbacks>> _records = {};
 
@@ -52,8 +54,6 @@ class MultiDragDispatcher extends Component implements MultiDragListener {
 
   Stream<DragCancelEvent> get onCancel => _dragCancelController.stream;
 
-  FlameGame get game => parent! as FlameGame;
-
   /// Called when the user initiates a drag gesture, for example by touching the
   /// screen and then moving the finger.
   ///
@@ -186,9 +186,17 @@ class MultiDragDispatcher extends Component implements MultiDragListener {
 
   //#endregion
 
+  static void addDispatcher(Component component) {
+    Dispatcher.addDispatcher(
+      component,
+      const MultiDragDispatcherKey(),
+      MultiDragDispatcher.new,
+    );
+  }
+
   @override
   void onMount() {
-    game.gestureDetectors.add<ImmediateMultiDragGestureRecognizer>(
+    game.gestureDetectors.register<ImmediateMultiDragGestureRecognizer>(
       ImmediateMultiDragGestureRecognizer.new,
       (ImmediateMultiDragGestureRecognizer instance) {
         instance.onStart = (Offset point) => FlameDragAdapter(this, point);
@@ -198,8 +206,8 @@ class MultiDragDispatcher extends Component implements MultiDragListener {
 
   @override
   void onRemove() {
-    game.gestureDetectors.remove<ImmediateMultiDragGestureRecognizer>();
-    game.unregisterKey(const MultiDragDispatcherKey());
+    game.gestureDetectors.unregister<ImmediateMultiDragGestureRecognizer>();
+    Dispatcher.removeDispatcher(game, const MultiDragDispatcherKey());
     _dragUpdateController.close();
     _dragCancelController.close();
     _dragStartController.close();