Relands "Wide gamut framework gradient test (#153976)" (#157643)

This was reverted because it failed to run. Colors were getting clamped
in the dithering fragment shader.

One change was made when relanding, i increased the epsilon for the
radial and conical gradients. They don't appear to give back the exact
color you asked for.

Do not land until https://github.com/flutter/engine/pull/56140 is rolled
into the framework.

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there for submitting PRs.
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responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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dev/integration_tests/wide_gamut_test/integration_test/app_test.dart

@@ -44,7 +44,8 @@ bool _isAlmost(double x, double y, double epsilon) {
 List<double> _deepRed = <double>[1.0931, -0.2268, -0.1501];
 
 bool _findRGBAF16Color(
-    Uint8List bytes, int width, int height, List<double> color) {
+    Uint8List bytes, int width, int height, List<double> color,
+    {required double epsilon}) {
   final ByteData byteData = ByteData.sublistView(bytes);
   expect(bytes.lengthInBytes, width * height * 8);
   expect(bytes.lengthInBytes, byteData.lengthInBytes);
@@ -54,9 +55,9 @@ bool _findRGBAF16Color(
     final double blue = _decodeHalf((pixel >> 32) & 0xffff);
     final double green = _decodeHalf((pixel >> 16) & 0xffff);
     final double red = _decodeHalf((pixel >> 0) & 0xffff);
-    if (_isAlmost(red, color[0], 0.01) &&
+    if (_isAlmost(red, color[0], epsilon) &&
-        _isAlmost(green, color[1], 0.01) &&
+        _isAlmost(green, color[1], epsilon) &&
-        _isAlmost(blue, color[2], 0.01)) {
+        _isAlmost(blue, color[2], epsilon)) {
       foundDeepRed = true;
     }
   }
@@ -64,7 +65,8 @@ bool _findRGBAF16Color(
 }
 
 bool _findBGRA10Color(
-    Uint8List bytes, int width, int height, List<double> color) {
+    Uint8List bytes, int width, int height, List<double> color,
+    {required double epsilon}) {
   final ByteData byteData = ByteData.sublistView(bytes);
   expect(bytes.lengthInBytes, width * height * 8);
   expect(bytes.lengthInBytes, byteData.lengthInBytes);
@@ -74,17 +76,17 @@ bool _findBGRA10Color(
     final double blue = _decodeBGR10((pixel >> 6) & 0x3ff);
     final double green = _decodeBGR10((pixel >> 22) & 0x3ff);
     final double red = _decodeBGR10((pixel >> 38) & 0x3ff);
-    if (_isAlmost(red, color[0], 0.01) &&
+    if (_isAlmost(red, color[0], epsilon) &&
-        _isAlmost(green, color[1], 0.01) &&
+        _isAlmost(green, color[1], epsilon) &&
-        _isAlmost(blue, color[2], 0.01)) {
+        _isAlmost(blue, color[2], epsilon)) {
       foundDeepRed = true;
     }
   }
   return foundDeepRed;
 }
 
-bool _findBGR10Color(
+bool _findBGR10Color(Uint8List bytes, int width, int height, List<double> color,
-    Uint8List bytes, int width, int height, List<double> color) {
+    {required double epsilon}) {
   final ByteData byteData = ByteData.sublistView(bytes);
   expect(bytes.lengthInBytes, width * height * 4);
   expect(bytes.lengthInBytes, byteData.lengthInBytes);
@@ -94,23 +96,27 @@ bool _findBGR10Color(
     final double blue = _decodeBGR10(pixel & 0x3ff);
     final double green = _decodeBGR10((pixel >> 10) & 0x3ff);
     final double red = _decodeBGR10((pixel >> 20) & 0x3ff);
-    if (_isAlmost(red, color[0], 0.01) &&
+    if (_isAlmost(red, color[0], epsilon) &&
-        _isAlmost(green, color[1], 0.01) &&
+        _isAlmost(green, color[1], epsilon) &&
-        _isAlmost(blue, color[2], 0.01)) {
+        _isAlmost(blue, color[2], epsilon)) {
       foundDeepRed = true;
     }
   }
   return foundDeepRed;
 }
 
-bool _findColor(List<dynamic> result, List<double> color) {
+bool _findColor(List<dynamic> result, List<double> color,
+    {double epsilon = 0.01}) {
   expect(result, isNotNull);
   expect(result.length, 4);
   final [int width, int height, String format, Uint8List bytes] = result;
   return switch (format) {
-    'MTLPixelFormatBGR10_XR'    => _findBGR10Color(bytes, width, height, color),
+    'MTLPixelFormatBGR10_XR' =>
-    'MTLPixelFormatBGRA10_XR'   => _findBGRA10Color(bytes, width, height, color),
+      _findBGR10Color(bytes, width, height, color, epsilon: epsilon),
-    'MTLPixelFormatRGBA16Float' => _findRGBAF16Color(bytes, width, height, color),
+    'MTLPixelFormatBGRA10_XR' =>
+      _findBGRA10Color(bytes, width, height, color, epsilon: epsilon),
+    'MTLPixelFormatRGBA16Float' =>
+      _findRGBAF16Color(bytes, width, height, color, epsilon: epsilon),
     _ => fail('Unsupported pixel format: $format'),
   };
 }
@@ -157,7 +163,8 @@ void main() {
       expect(_findColor(result, _deepRed), isTrue);
       expect(_findColor(result, <double>[0.0, 1.0, 0.0]), isTrue);
     });
-    testWidgets('draw image with wide gamut works', (WidgetTester tester) async {
+    testWidgets('draw image with wide gamut works',
+        (WidgetTester tester) async {
       app.run(app.Setup.drawnImage);
       await tester.pumpAndSettle(const Duration(seconds: 2));
 
@@ -166,7 +173,8 @@ void main() {
           await channel.invokeMethod('test') as List<Object?>;
       expect(_findColor(result, <double>[0.0, 1.0, 0.0]), isTrue);
     });
-    testWidgets('draw container with wide gamut works', (WidgetTester tester) async {
+    testWidgets('draw container with wide gamut works',
+        (WidgetTester tester) async {
       app.run(app.Setup.container);
       await tester.pumpAndSettle(const Duration(seconds: 2));
 
@@ -175,5 +183,49 @@ void main() {
           await channel.invokeMethod('test') as List<Object?>;
       expect(_findColor(result, _deepRed), isTrue);
     });
+
+    testWidgets('draw wide gamut linear gradient works',
+        (WidgetTester tester) async {
+      app.run(app.Setup.linearGradient);
+      await tester.pumpAndSettle(const Duration(seconds: 2));
+
+      const MethodChannel channel = MethodChannel('flutter/screenshot');
+      final List<Object?> result =
+          await channel.invokeMethod('test') as List<Object?>;
+      expect(_findColor(result, _deepRed), isTrue);
+    });
+
+    testWidgets('draw wide gamut radial gradient works',
+        (WidgetTester tester) async {
+      app.run(app.Setup.radialGradient);
+      await tester.pumpAndSettle(const Duration(seconds: 2));
+
+      const MethodChannel channel = MethodChannel('flutter/screenshot');
+      final List<Object?> result =
+          await channel.invokeMethod('test') as List<Object?>;
+      expect(_findColor(result, _deepRed, epsilon: 0.05), isTrue);
+    });
+
+    testWidgets('draw wide gamut conical gradient works',
+        (WidgetTester tester) async {
+      app.run(app.Setup.conicalGradient);
+      await tester.pumpAndSettle(const Duration(seconds: 2));
+
+      const MethodChannel channel = MethodChannel('flutter/screenshot');
+      final List<Object?> result =
+          await channel.invokeMethod('test') as List<Object?>;
+      expect(_findColor(result, _deepRed, epsilon: 0.05), isTrue);
+    });
+
+    testWidgets('draw wide gamut sweep gradient works',
+        (WidgetTester tester) async {
+      app.run(app.Setup.sweepGradient);
+      await tester.pumpAndSettle(const Duration(seconds: 2));
+
+      const MethodChannel channel = MethodChannel('flutter/screenshot');
+      final List<Object?> result =
+          await channel.invokeMethod('test') as List<Object?>;
+      expect(_findColor(result, _deepRed), isTrue);
+    });
   });
 }

dev/integration_tests/wide_gamut_test/lib/main.dart

@@ -137,7 +137,7 @@ const String _displayP3Logo =
     'gr3yrjmlwqXLjmWw1O2I5Wmp9Xxjyh+AVIZ6ADIAqcwClakzeMgApDILVKbO4CED'
     'kMosUJk6g4dUBuRfvf1am9VRqzYAAAAASUVORK5CYII=';
 
-void main() => run(Setup.container);
+void main() => run(Setup.sweepGradient);
 
 enum Setup {
   none,
@@ -146,6 +146,10 @@ enum Setup {
   blur,
   drawnImage,
   container,
+  linearGradient,
+  radialGradient,
+  conicalGradient,
+  sweepGradient,
 }
 
 void run(Setup setup) {
@@ -265,7 +269,14 @@ class _MyHomePageState extends State<MyHomePage> {
         _loadImage().then((ui.Image? value) => setState(() { _image = value; }));
       case Setup.drawnImage:
         _drawImage().then((ui.Image? value) => setState(() { _image = value; }));
-      case Setup.image || Setup.blur || Setup.none || Setup.container:
+      case Setup.image ||
+            Setup.blur ||
+            Setup.none ||
+            Setup.container ||
+            Setup.linearGradient ||
+            Setup.radialGradient ||
+            Setup.conicalGradient ||
+            Setup.sweepGradient:
         break;
     }
     super.initState();
@@ -308,6 +319,97 @@ class _MyHomePageState extends State<MyHomePage> {
                 green: 0,
                 blue: 0,
                 colorSpace: ui.ColorSpace.displayP3));
+      case Setup.linearGradient:
+        imageWidget = Container(
+          width: 100,
+          height: 100,
+          decoration: const BoxDecoration(
+            gradient: LinearGradient(
+              begin: Alignment.topLeft,
+              end: Alignment.bottomRight,
+              colors: <Color>[
+                Color.from(
+                  alpha: 1,
+                  red: 1,
+                  green: 0,
+                  blue: 0,
+                  colorSpace: ui.ColorSpace.displayP3),
+                Color.from(
+                  alpha: 1,
+                  red: 0,
+                  green: 1,
+                  blue: 0,
+                  colorSpace: ui.ColorSpace.displayP3)],
+            ),
+          ),
+        );
+      case Setup.radialGradient:
+        imageWidget = Container(
+          width: 100,
+          height: 100,
+          decoration: const BoxDecoration(
+            gradient: RadialGradient(
+              colors: <Color>[
+                Color.from(
+                  alpha: 1,
+                  red: 1,
+                  green: 0,
+                  blue: 0,
+                  colorSpace: ui.ColorSpace.displayP3),
+                Color.from(
+                  alpha: 1,
+                  red: 0,
+                  green: 1,
+                  blue: 0,
+                  colorSpace: ui.ColorSpace.displayP3)],
+            ),
+          ),
+        );
+      case Setup.conicalGradient:
+        imageWidget = Container(
+          width: 100,
+          height: 100,
+          decoration: const BoxDecoration(
+            gradient: RadialGradient(
+              focal: Alignment(0.2, 0.2),
+              colors: <Color>[
+                Color.from(
+                  alpha: 1,
+                  red: 1,
+                  green: 0,
+                  blue: 0,
+                  colorSpace: ui.ColorSpace.displayP3),
+                Color.from(
+                  alpha: 1,
+                  red: 0,
+                  green: 1,
+                  blue: 0,
+                  colorSpace: ui.ColorSpace.displayP3)],
+            ),
+          ),
+        );
+      case Setup.sweepGradient:
+        imageWidget = Container(
+          width: 100,
+          height: 100,
+          decoration: const BoxDecoration(
+            gradient: SweepGradient(
+              colors: <Color>[
+                Color.from(
+                  alpha: 1,
+                  red: 1,
+                  green: 0,
+                  blue: 0,
+                  colorSpace: ui.ColorSpace.displayP3),
+                Color.from(
+                  alpha: 1,
+                  red: 0,
+                  green: 1,
+                  blue: 0,
+                  colorSpace: ui.ColorSpace.displayP3)],
+            ),
+          ),
+        );
     }
 
     return Scaffold(