fix: Use ComponentKeys to keep track of dispatchers (#2629)

This uses the `ComponentKey` API to register and unregister dispatchers,
so that we don't have to create unnecessary dispatcher components that
are removed directly in `onMount` if there already is a dispatcher or
the same type added.

This also opens up for registering components to the dispatchers so that
we don't have to go through the whole tree to deliver events which it
does currently.

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

@@ -30,8 +30,10 @@ mixin DoubleTapCallbacks on Component {
   void onMount() {
     super.onMount();
     final game = findGame()! as FlameGame;
-    if (game.firstChild<DoubleTapDispatcher>() == null) {
-      game.add(DoubleTapDispatcher());
+    if (game.findByKey(const DoubleTapDispatcherKey()) == null) {
+      final dispatcher = DoubleTapDispatcher();
+      game.registerKey(const DoubleTapDispatcherKey(), dispatcher);
+      game.add(dispatcher);
     }
   }
 }

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

@@ -67,8 +67,10 @@ mixin DragCallbacks on Component {
   void onMount() {
     super.onMount();
     final game = findGame()! as FlameGame;
-    if (game.firstChild<MultiDragDispatcher>() == null) {
-      game.add(MultiDragDispatcher());
+    if (game.findByKey(const MultiDragDispatcherKey()) == null) {
+      final dispatcher = MultiDragDispatcher();
+      game.registerKey(const MultiDragDispatcherKey(), dispatcher);
+      game.add(dispatcher);
     }
   }
 }

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

@@ -24,8 +24,10 @@ mixin TapCallbacks on Component {
   void onMount() {
     super.onMount();
     final game = findGame()! as FlameGame;
-    if (game.firstChild<MultiTapDispatcher>() == null) {
-      game.add(MultiTapDispatcher());
+    if (game.findByKey(const MultiTapDispatcherKey()) == null) {
+      final dispatcher = MultiTapDispatcher();
+      game.registerKey(const MultiTapDispatcherKey(), dispatcher);
+      game.add(dispatcher);
     }
   }
 }

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

@@ -7,14 +7,24 @@ import 'package:flame/src/events/messages/double_tap_event.dart';
 import 'package:flutter/gestures.dart';
 import 'package:meta/meta.dart';
 
+class DoubleTapDispatcherKey implements ComponentKey {
+  const DoubleTapDispatcherKey();
+
+  @override
+  int get hashCode => 20260645; // 'DoubleTapDispatcherKey' as hashCode
+
+  @override
+  bool operator ==(dynamic other) =>
+      other is DoubleTapDispatcherKey && other.hashCode == hashCode;
+}
+
 /// [DoubleTapDispatcher] propagates double-tap events to every components in
 /// 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.
 @internal
 class DoubleTapDispatcher extends Component with HasGameRef<FlameGame> {
   final _components = <DoubleTapCallbacks>{};
-  bool _eventHandlerRegistered = false;
 
   void _onDoubleTapDown(DoubleTapDownEvent event) {
     event.deliverAtPoint(
@@ -37,30 +47,21 @@ class DoubleTapDispatcher extends Component with HasGameRef<FlameGame> {
 
   @override
   void onMount() {
-    if (game.firstChild<DoubleTapDispatcher>() == null) {
-      game.gestureDetectors.add(
-        DoubleTapGestureRecognizer.new,
-        (DoubleTapGestureRecognizer instance) {
-          instance.onDoubleTapDown =
-              (details) => _onDoubleTapDown(DoubleTapDownEvent(game, details));
-          instance.onDoubleTapCancel =
-              () => _onDoubleTapCancel(DoubleTapCancelEvent());
-          instance.onDoubleTap = () => _onDoubleTapUp(DoubleTapEvent());
-        },
-      );
-      _eventHandlerRegistered = true;
-    } else {
-      removeFromParent();
-    }
+    game.gestureDetectors.add(
+      DoubleTapGestureRecognizer.new,
+      (DoubleTapGestureRecognizer instance) {
+        instance.onDoubleTapDown =
+            (details) => _onDoubleTapDown(DoubleTapDownEvent(game, details));
+        instance.onDoubleTapCancel =
+            () => _onDoubleTapCancel(DoubleTapCancelEvent());
+        instance.onDoubleTap = () => _onDoubleTapUp(DoubleTapEvent());
+      },
+    );
   }
 
   @override
   void onRemove() {
-    if (!_eventHandlerRegistered) {
-      return;
-    }
-
     game.gestureDetectors.remove<DoubleTapGestureRecognizer>();
-    _eventHandlerRegistered = false;
+    game.unregisterKey(const DoubleTapDispatcherKey());
   }
 }

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

@@ -1,4 +1,5 @@
 import 'package:flame/src/components/core/component.dart';
+import 'package:flame/src/components/core/component_key.dart';
 import 'package:flame/src/components/mixins/draggable.dart';
 import 'package:flame/src/events/component_mixins/drag_callbacks.dart';
 import 'package:flame/src/events/flame_drag_adapter.dart';
@@ -14,6 +15,17 @@ import 'package:flame/src/game/game_render_box.dart';
 import 'package:flutter/gestures.dart';
 import 'package:meta/meta.dart';
 
+class MultiDragDispatcherKey implements ComponentKey {
+  const MultiDragDispatcherKey();
+
+  @override
+  int get hashCode => 91604879; // 'MultiDragDispatcherKey' as hashCode
+
+  @override
+  bool operator ==(dynamic other) =>
+      other is MultiDragDispatcherKey && other.hashCode == hashCode;
+}
+
 /// **MultiDragDispatcher** facilitates dispatching of drag events to the
 /// [DragCallbacks] components in the component tree. It will be attached to
 /// the [FlameGame] instance automatically whenever any [DragCallbacks]
@@ -22,7 +34,6 @@ import 'package:meta/meta.dart';
 class MultiDragDispatcher extends Component implements MultiDragListener {
   /// The record of all components currently being touched.
   final Set<TaggedComponent<DragCallbacks>> _records = {};
-  bool _eventHandlerRegistered = false;
 
   FlameGame get game => parent! as FlameGame;
 
@@ -165,26 +176,18 @@ class MultiDragDispatcher extends Component implements MultiDragListener {
 
   @override
   void onMount() {
-    if (game.firstChild<MultiDragDispatcher>() == null) {
-      game.gestureDetectors.add<ImmediateMultiDragGestureRecognizer>(
-        ImmediateMultiDragGestureRecognizer.new,
-        (ImmediateMultiDragGestureRecognizer instance) {
-          instance.onStart = (Offset point) => FlameDragAdapter(this, point);
-        },
-      );
-      _eventHandlerRegistered = true;
-    } else {
-      // Ensures that only one MultiDragDispatcher is attached to the Game.
-      removeFromParent();
-    }
+    game.gestureDetectors.add<ImmediateMultiDragGestureRecognizer>(
+      ImmediateMultiDragGestureRecognizer.new,
+      (ImmediateMultiDragGestureRecognizer instance) {
+        instance.onStart = (Offset point) => FlameDragAdapter(this, point);
+      },
+    );
   }
 
   @override
   void onRemove() {
-    if (_eventHandlerRegistered) {
-      game.gestureDetectors.remove<ImmediateMultiDragGestureRecognizer>();
-      _eventHandlerRegistered = false;
-    }
+    game.gestureDetectors.remove<ImmediateMultiDragGestureRecognizer>();
+    game.unregisterKey(const MultiDragDispatcherKey());
   }
 
   @override

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

@@ -11,11 +11,21 @@ import 'package:flame/src/game/game_render_box.dart';
 import 'package:flutter/gestures.dart';
 import 'package:meta/meta.dart';
 
+class MultiTapDispatcherKey implements ComponentKey {
+  const MultiTapDispatcherKey();
+
+  @override
+  int get hashCode => 401913931; // 'MultiTapDispatcherKey' as hashCode
+
+  @override
+  bool operator ==(dynamic other) =>
+      other is MultiTapDispatcherKey && other.hashCode == hashCode;
+}
+
 @internal
 class MultiTapDispatcher extends Component implements MultiTapListener {
   /// The record of all components currently being touched.
   final Set<TaggedComponent<TapCallbacks>> _record = {};
-  bool _eventHandlerRegistered = false;
 
   FlameGame get game => parent! as FlameGame;
 
@@ -179,33 +189,25 @@ class MultiTapDispatcher extends Component implements MultiTapListener {
 
   @override
   void onMount() {
-    if (game.firstChild<MultiTapDispatcher>() == null) {
-      game.gestureDetectors.add<MultiTapGestureRecognizer>(
-        MultiTapGestureRecognizer.new,
-        (MultiTapGestureRecognizer instance) {
-          instance.longTapDelay = Duration(
-            milliseconds: (longTapDelay * 1000).toInt(),
-          );
-          instance.onTap = handleTap;
-          instance.onTapDown = handleTapDown;
-          instance.onTapUp = handleTapUp;
-          instance.onTapCancel = handleTapCancel;
-          instance.onLongTapDown = handleLongTapDown;
-        },
-      );
-      _eventHandlerRegistered = true;
-    } else {
-      // Ensures that only one MultiTapDispatcher is attached to the Game.
-      removeFromParent();
-    }
+    game.gestureDetectors.add<MultiTapGestureRecognizer>(
+      MultiTapGestureRecognizer.new,
+      (MultiTapGestureRecognizer instance) {
+        instance.longTapDelay = Duration(
+          milliseconds: (longTapDelay * 1000).toInt(),
+        );
+        instance.onTap = handleTap;
+        instance.onTapDown = handleTapDown;
+        instance.onTapUp = handleTapUp;
+        instance.onTapCancel = handleTapCancel;
+        instance.onLongTapDown = handleLongTapDown;
+      },
+    );
   }
 
   @override
   void onRemove() {
-    if (_eventHandlerRegistered) {
-      game.gestureDetectors.remove<MultiTapGestureRecognizer>();
-      _eventHandlerRegistered = false;
-    }
+    game.gestureDetectors.remove<MultiTapGestureRecognizer>();
+    game.unregisterKey(const MultiTapDispatcherKey());
   }
 
   @override