[Material] Create an InkSparkle splash effect that matches the Material 3 ripple effect (#99731)

Create an InkSparkle effect that matches the Material 3 ripple on Android 12. Similar to InkRipple, but uses the new custom shader API.

packages/flutter/lib/material.dart

@@ -87,6 +87,7 @@ export 'src/material/icons.dart';
 export 'src/material/ink_decoration.dart';
 export 'src/material/ink_highlight.dart';
 export 'src/material/ink_ripple.dart';
+export 'src/material/ink_sparkle.dart';
 export 'src/material/ink_splash.dart';
 export 'src/material/ink_well.dart';
 export 'src/material/input_border.dart';

packages/flutter/test/material/ink_sparkle_test.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file is run as part of a reduced test set in CI on Mac and Windows
+// machines.
+@Tags(<String>['reduced-test-set'])
+
+import 'package:flutter/material.dart';
+import 'package:flutter/src/foundation/constants.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../rendering/mock_canvas.dart';
+
+void main() {
+  testWidgets('InkSparkle in a Button compiles and does not crash', (WidgetTester tester) async {
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        body: Center(
+          child: ElevatedButton(
+            style: ElevatedButton.styleFrom(splashFactory: InkSparkle.splashFactory),
+            child: const Text('Sparkle!'),
+            onPressed: () { },
+          ),
+        ),
+      ),
+    ));
+    final Finder buttonFinder = find.text('Sparkle!');
+    await tester.tap(buttonFinder);
+    await tester.pump();
+    await tester.pumpAndSettle();
+  },
+    skip: kIsWeb, // [intended] SPIR-V shaders are not yet supported for web.
+  );
+
+  testWidgets('InkSparkle default splashFactory paints with drawRect when bounded', (WidgetTester tester) async {
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        body: Center(
+          child: InkWell(
+            splashFactory: InkSparkle.splashFactory,
+            child: const Text('Sparkle!'),
+            onTap: () { },
+          ),
+        ),
+      ),
+    ));
+    final Finder buttonFinder = find.text('Sparkle!');
+    await tester.tap(buttonFinder);
+    await tester.pump();
+    await tester.pumpAndSettle();
+
+    final MaterialInkController material = Material.of(tester.element(buttonFinder))!;
+    await tester.pump(const Duration(milliseconds: 200));
+    expect(material, paintsExactlyCountTimes(#drawRect, 1));
+  },
+    skip: kIsWeb, // [intended] SPIR-V shaders are not yet supported for web.
+  );
+
+    testWidgets('InkSparkle default splashFactory paints with drawPaint when unbounded', (WidgetTester tester) async {
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        body: Center(
+          child: InkResponse(
+            splashFactory: InkSparkle.splashFactory,
+            child: const Text('Sparkle!'),
+            onTap: () { },
+          ),
+        ),
+      ),
+    ));
+    final Finder buttonFinder = find.text('Sparkle!');
+    await tester.tap(buttonFinder);
+    await tester.pump();
+    await tester.pumpAndSettle();
+
+    final MaterialInkController material = Material.of(tester.element(buttonFinder))!;
+    await tester.pump(const Duration(milliseconds: 200));
+    expect(material, paintsExactlyCountTimes(#drawPaint, 1));
+  },
+    skip: kIsWeb, // [intended] SPIR-V shaders are not yet supported for web.
+  );
+
+  /////////////
+  // Goldens //
+  /////////////
+
+  testWidgets('InkSparkle renders with sparkles when top left of button is tapped', (WidgetTester tester) async {
+    await _runTest(tester, 'top_left', 0.2);
+  },
+    skip: kIsWeb, // [intended] SPIR-V shaders are not yet supported for web.
+  );
+
+  testWidgets('InkSparkle renders with sparkles when center of button is tapped', (WidgetTester tester) async {
+    await _runTest(tester, 'center', 0.5);
+  },
+    skip: kIsWeb, // [intended] SPIR-V shaders are not yet supported for web.
+  );
+
+  testWidgets('InkSparkle renders with sparkles when bottom right of button is tapped', (WidgetTester tester) async {
+    await _runTest(tester, 'bottom_right', 0.8);
+  },
+    skip: kIsWeb, // [intended] SPIR-V shaders are not yet supported for web.
+  );
+}
+
+Future<void> _runTest(WidgetTester tester, String positionName, double distanceFromTopLeft) async {
+  final Key repaintKey = UniqueKey();
+  final Key buttonKey = UniqueKey();
+
+  await tester.pumpWidget(MaterialApp(
+    home: Scaffold(
+      body: Center(
+        child: RepaintBoundary(
+          key: repaintKey,
+          child: ElevatedButton(
+            key: buttonKey,
+            style: ElevatedButton.styleFrom(splashFactory: InkSparkle.constantTurbulenceSeedSplashFactory),
+            child: const Text('Sparkle!'),
+            onPressed: () { },
+          ),
+        ),
+      ),
+    ),
+  ));
+
+  final Finder buttonFinder = find.byKey(buttonKey);
+  final Finder repaintFinder = find.byKey(repaintKey);
+
+  await _warmUpShader(tester, buttonFinder);
+
+  final Offset topLeft = tester.getTopLeft(buttonFinder);
+  final Offset bottomRight = tester.getBottomRight(buttonFinder);
+
+  final Offset target = topLeft + (bottomRight - topLeft) * distanceFromTopLeft;
+  await tester.tapAt(target);
+  for (int i = 0; i <= 5; i++) {
+    await tester.pump(const Duration(milliseconds: 50));
+    await expectLater(
+      repaintFinder,
+      matchesGoldenFile('ink_sparkle.$positionName.$i.png'),
+    );
+  }
+}
+
+// Warm up shader. Compilation is of the order of 10 milliseconds and
+// Animation is < 1000 milliseconds. Use 2000 milliseconds as a safety
+// net to prevent flakiness.
+Future<void> _warmUpShader(WidgetTester tester, Finder buttonFinder) async {
+  await tester.tap(buttonFinder);
+  await tester.pumpAndSettle(const Duration(milliseconds: 2000));
+}