Implement pausing (#37)

fireworks/lib/src/foundation/controller.dart

@@ -63,6 +63,7 @@ class FireworkController implements Listenable {
   double _globalHue = 42;
 
   late final Ticker _ticker;
+  var _paused = false;
 
   /// Starts the firework show.
   ///
@@ -74,6 +75,22 @@ class FireworkController implements Listenable {
     _ticker = vsync.createTicker(_update)..start();
   }
 
+  /// Pauses the firework show.
+  ///
+  /// Can only be called while the firework show is running.
+  void pause() {
+    assert(!_paused);
+    _paused = true;
+  }
+
+  /// Resumes the firework show.
+  ///
+  /// Can only be called while the firework show is paused.
+  void resume() {
+    assert(_paused);
+    _paused = false;
+  }
+
   final List<VoidCallback> _listeners;
 
   @override
@@ -127,6 +144,8 @@ class FireworkController implements Listenable {
   Duration _lastRocketSpawn = Duration.zero;
 
   void _update(Duration elapsedDuration) {
+    if (_paused) return;
+
     if (windowSize == Size.zero) {
       // We need to wait until we have the size.
       return;

fireworks_demo/lib/main.dart

@@ -55,6 +55,7 @@ class _FireworksState extends State<_Fireworks>
   );
 
   var _showInfoOverlay = false;
+  var _isPaused = false;
 
   @override
   void dispose() {
@@ -75,6 +76,16 @@ class _FireworksState extends State<_Fireworks>
           _showInfoOverlay = !_showInfoOverlay;
         });
       },
+      onSecondaryTap: () {
+        setState(() {
+          _isPaused = !_isPaused;
+          if (!_isPaused) {
+            _controller.pause();
+          } else {
+            _controller.resume();
+          }
+        });
+      },
       child: Stack(
         children: [
           Fireworks(
@@ -151,6 +162,7 @@ class _FireworksState extends State<_Fireworks>
                               Text(
                                 'Hover with your mouse to launch fireworks to '
                                 'your mouse :)\n'
+                                'Right click to pause/resume the animation.\n'
                                 'Or just lean back and enjoy the show (:\n\n'
                                 'Click again to close this.',
                                 textAlign: TextAlign.center,

fireworks_demo/pubspec.lock

@@ -17,13 +17,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.3.0"
-  charcode:
-    dependency: transitive
-    description:
-      name: charcode
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.3.1"
   collection:
     dependency: transitive
     description:
@@ -89,13 +82,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "4.0.2"
-  js:
-    dependency: transitive
-    description:
-      name: js
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.6.4"
   material_color_utilities:
     dependency: transitive
     description: