Revert "Perform no shader warm-up by default (#87126)"

This reverts commit 32c2e2b.

dev/tracing_tests/test/image_cache_tracing_test.dart

@@ -55,7 +55,7 @@ void main() {
         },
         <String, dynamic>{
           'name': 'listener',
-          'args': <String, dynamic>{'parentId': '0', 'isolateId': isolateId}
+          'args': <String, dynamic>{'parentId': '1', 'isolateId': isolateId}
         },
         <String, dynamic>{
           'name': 'ImageCache.clear',

examples/layers/raw/shader_warm_up.dart

@@ -0,0 +1,35 @@
+// 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 example shows the draw operations to warm up the GPU shaders by default.
+
+import 'dart:ui' as ui;
+
+import 'package:flutter/material.dart';
+
+Future<void> beginFrame(Duration timeStamp) async {
+  // PAINT
+  final ui.PictureRecorder recorder = ui.PictureRecorder();
+  const ui.Rect paintBounds = ui.Rect.fromLTRB(0, 0, 1000, 1000);
+  final ui.Canvas canvas = ui.Canvas(recorder, paintBounds);
+  final ui.Paint backgroundPaint = ui.Paint()..color = Colors.white;
+  canvas.drawRect(paintBounds, backgroundPaint);
+  await const DefaultShaderWarmUp(
+    drawCallSpacing: 80.0,
+    canvasSize: ui.Size(1024, 1024),
+  ).warmUpOnCanvas(canvas);
+  final ui.Picture picture = recorder.endRecording();
+
+  // COMPOSITE
+  final ui.SceneBuilder sceneBuilder = ui.SceneBuilder()
+    ..pushClipRect(paintBounds)
+    ..addPicture(ui.Offset.zero, picture)
+    ..pop();
+  ui.window.render(sceneBuilder.build());
+}
+
+Future<void> main() async {
+  ui.window.onBeginFrame = beginFrame;
+  ui.window.scheduleFrame();
+}

examples/layers/test/smoketests/raw/shader_warm_up_test.dart

@@ -0,0 +1,14 @@
+// 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.
+
+// ignore: deprecated_member_use
+import 'package:test_api/test_api.dart' hide TypeMatcher, isInstanceOf;
+
+import '../../../raw/shader_warm_up.dart' as demo;
+
+void main() {
+  test('layers smoketest for raw/shader_warm_up.dart', () {
+    demo.main();
+  });
+}

packages/flutter/lib/src/painting/binding.dart

@@ -31,17 +31,17 @@ mixin PaintingBinding on BindingBase, ServicesBinding {
 
   /// [ShaderWarmUp] instance to be executed during [initInstances].
   ///
-  /// Defaults to `null`, meaning no shader warm-up is done. Some platforms may
-  /// not support shader warm-up before at least one frame has been displayed.
+  /// Defaults to an instance of [DefaultShaderWarmUp].
   ///
   /// If the application has scenes that require the compilation of complex
-  /// shaders, it may cause jank in the middle of an animation or interaction.
-  /// In that case, setting [shaderWarmUp] to a custom [ShaderWarmUp] before
-  /// creating the binding (usually before [runApp] for normal Flutter apps, and
-  /// before [enableFlutterDriverExtension] for Flutter driver tests) may help
-  /// if that object paints the difficult scene in its
-  /// [ShaderWarmUp.warmUpOnCanvas] method, as this allows Flutter to
-  /// pre-compile and cache the required shaders during startup.
+  /// shaders that are not covered by [DefaultShaderWarmUp], it may cause jank
+  /// in the middle of an animation or interaction. In that case, setting
+  /// [shaderWarmUp] to a custom [ShaderWarmUp] before creating the binding
+  /// (usually before [runApp] for normal Flutter apps, and before
+  /// [enableFlutterDriverExtension] for Flutter driver tests) may help if that
+  /// object paints the difficult scene in its [ShaderWarmUp.warmUpOnCanvas]
+  /// method, as this allows Flutter to pre-compile and cache the required
+  /// shaders during startup.
   ///
   /// Currently the warm-up happens synchronously on the raster thread which
   /// means the rendering of the first frame on the raster thread will be
@@ -58,7 +58,7 @@ mixin PaintingBinding on BindingBase, ServicesBinding {
   ///
   ///  * [ShaderWarmUp], the interface for implementing custom warm-up scenes.
   ///  * <https://flutter.dev/docs/perf/rendering/shader>
-  static ShaderWarmUp? shaderWarmUp;
+  static ShaderWarmUp? shaderWarmUp = const DefaultShaderWarmUp();
 
   /// The singleton that implements the Flutter framework's image cache.
   ///

packages/flutter/lib/src/painting/shader_warm_up.dart

@@ -17,11 +17,12 @@ import 'debug.dart';
 /// jank in the middle of an animation.
 ///
 /// Therefore, we use this during the [PaintingBinding.initInstances] call to
-/// move common shader compilations from animation time to startup time. If
-/// needed, app developers can create a custom [ShaderWarmUp] subclass and
-/// hand it to [PaintingBinding.shaderWarmUp] before
-/// [PaintingBinding.initInstances] is called. Usually, that can be done before
-/// calling [runApp].
+/// move common shader compilations from animation time to startup time. By
+/// default, a [DefaultShaderWarmUp] is used. If needed, app developers can
+/// create a custom [ShaderWarmUp] subclass and hand it to
+/// [PaintingBinding.shaderWarmUp] (so it replaces [DefaultShaderWarmUp])
+/// before [PaintingBinding.initInstances] is called. Usually, that can be
+/// done before calling [runApp].
 ///
 /// To determine whether a draw operation is useful for warming up shaders,
 /// check whether it improves the slowest frame rasterization time. Also,
@@ -101,3 +102,141 @@ abstract class ShaderWarmUp {
     picture.dispose();
   }
 }
+
+/// Default way of warming up Skia shader compilations.
+///
+/// The draw operations being warmed up here are decided according to Flutter
+/// engineers' observation and experience based on the apps and the performance
+/// issues seen so far.
+///
+/// This is used for the default value of [PaintingBinding.shaderWarmUp].
+/// Consider setting that static property to a different value before the
+/// binding is initialized to change the warm-up sequence.
+///
+/// See also:
+///
+///  * [ShaderWarmUp], the base class for shader warm-up objects.
+///  * <https://flutter.dev/docs/perf/rendering/shader>
+class DefaultShaderWarmUp extends ShaderWarmUp {
+  /// Create an instance of the default shader warm-up logic.
+  ///
+  /// Since this constructor is `const`, [DefaultShaderWarmUp] can be used as
+  /// the default value of parameters.
+  const DefaultShaderWarmUp({
+    this.drawCallSpacing = 0.0,
+    this.canvasSize = const ui.Size(100.0, 100.0),
+  });
+
+  /// Distance to place between draw calls for visualizing the draws for
+  /// debugging purposes (e.g. 80.0).
+  ///
+  /// Defaults to 0.0.
+  ///
+  /// When changing this value, the [canvasSize] must also be changed to
+  /// accommodate the bigger canvas.
+  final double drawCallSpacing;
+
+  /// The [size] of the canvas required to paint the shapes in [warmUpOnCanvas].
+  ///
+  /// When [drawCallSpacing] is 0.0, this should be at least 100.0 by 100.0.
+  final ui.Size canvasSize;
+
+  @override
+  ui.Size get size => canvasSize;
+
+  /// Trigger common draw operations on a canvas to warm up GPU shader
+  /// compilation cache.
+  @override
+  Future<void> warmUpOnCanvas(ui.Canvas canvas) async {
+    const ui.RRect rrect = ui.RRect.fromLTRBXY(20.0, 20.0, 60.0, 60.0, 10.0, 10.0);
+    final ui.Path rrectPath = ui.Path()..addRRect(rrect);
+    final ui.Path circlePath = ui.Path()..addOval(
+      ui.Rect.fromCircle(center: const ui.Offset(40.0, 40.0), radius: 20.0),
+    );
+
+    // The following path is based on
+    // https://skia.org/user/api/SkCanvas_Reference#SkCanvas_drawPath
+    final ui.Path path = ui.Path();
+    path.moveTo(20.0, 60.0);
+    path.quadraticBezierTo(60.0, 20.0, 60.0, 60.0);
+    path.close();
+    path.moveTo(60.0, 20.0);
+    path.quadraticBezierTo(60.0, 60.0, 20.0, 60.0);
+
+    final ui.Path convexPath = ui.Path();
+    convexPath.moveTo(20.0, 30.0);
+    convexPath.lineTo(40.0, 20.0);
+    convexPath.lineTo(60.0, 30.0);
+    convexPath.lineTo(60.0, 60.0);
+    convexPath.lineTo(20.0, 60.0);
+    convexPath.close();
+
+    // Skia uses different shaders based on the kinds of paths being drawn and
+    // the associated paint configurations. According to our experience and
+    // tracing, drawing the following paths/paints generates various of
+    // shaders that are commonly used.
+    final List<ui.Path> paths = <ui.Path>[rrectPath, circlePath, path, convexPath];
+
+    final List<ui.Paint> paints = <ui.Paint>[
+      ui.Paint()
+        ..isAntiAlias = true
+        ..style = ui.PaintingStyle.fill,
+      ui.Paint()
+        ..isAntiAlias = false
+        ..style = ui.PaintingStyle.fill,
+      ui.Paint()
+        ..isAntiAlias = true
+        ..style = ui.PaintingStyle.stroke
+        ..strokeWidth = 10,
+      ui.Paint()
+        ..isAntiAlias = true
+        ..style = ui.PaintingStyle.stroke
+        ..strokeWidth = 0.1,  // hairline
+    ];
+
+    // Warm up path stroke and fill shaders.
+    for (int i = 0; i < paths.length; i += 1) {
+      canvas.save();
+      for (final ui.Paint paint in paints) {
+        canvas.drawPath(paths[i], paint);
+        canvas.translate(drawCallSpacing, 0.0);
+      }
+      canvas.restore();
+      canvas.translate(0.0, drawCallSpacing);
+    }
+
+    // Warm up shadow shaders.
+    const ui.Color black = ui.Color(0xFF000000);
+    canvas.save();
+    canvas.drawShadow(rrectPath, black, 10.0, true);
+    canvas.translate(drawCallSpacing, 0.0);
+    canvas.drawShadow(rrectPath, black, 10.0, false);
+    canvas.restore();
+
+    // Warm up text shaders.
+    canvas.translate(0.0, drawCallSpacing);
+    final ui.ParagraphBuilder paragraphBuilder = ui.ParagraphBuilder(
+      ui.ParagraphStyle(textDirection: ui.TextDirection.ltr),
+    )..pushStyle(ui.TextStyle(color: black))..addText('_');
+    final ui.Paragraph paragraph = paragraphBuilder.build()
+      ..layout(const ui.ParagraphConstraints(width: 60.0));
+    canvas.drawParagraph(paragraph, const ui.Offset(20.0, 20.0));
+
+    // Draw a rect inside a rrect with a non-trivial intersection. If the
+    // intersection is trivial (e.g., equals the rrect clip), Skia will optimize
+    // the clip out.
+    //
+    // Add an integral or fractional translation to trigger Skia's non-AA or AA
+    // optimizations (as did before in normal FillRectOp in rrect clip cases).
+    for (final double fraction in <double>[0.0, 0.5]) {
+      canvas
+        ..save()
+        ..translate(fraction, fraction)
+        ..clipRRect(ui.RRect.fromLTRBR(8, 8, 328, 248, const ui.Radius.circular(16)))
+        ..drawRect(const ui.Rect.fromLTRB(10, 10, 320, 240), ui.Paint())
+        ..restore();
+      canvas.translate(drawCallSpacing, 0.0);
+    }
+    canvas.translate(0.0, drawCallSpacing);
+  }
+}

packages/flutter/test/painting/binding_test.dart

@@ -38,10 +38,6 @@ Future<void> main() async {
     expect(binding.imageCache.clearCount, 1);
     expect(binding.imageCache.liveClearCount, 1);
   });
-
-  test('ShaderWarmUp is null by default', () {
-    expect(PaintingBinding.shaderWarmUp, null);
-  });
 }
 
 class TestBindingBase implements BindingBase {

packages/flutter/test/painting/shader_warm_up_test.dart

@@ -0,0 +1,61 @@
+// 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.
+
+import 'dart:ui' as ui;
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/painting.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+class TestCanvas implements Canvas {
+  TestCanvas();
+
+  final List<Invocation> invocations = <Invocation>[];
+
+  @override
+  void noSuchMethod(Invocation invocation) {
+    invocations.add(invocation);
+  }
+}
+
+void main() {
+  test('DefaultShaderWarmUp has expected canvas invocations', () {
+    final TestCanvas canvas = TestCanvas();
+    const DefaultShaderWarmUp s = DefaultShaderWarmUp();
+    s.warmUpOnCanvas(canvas);
+
+    bool hasDrawRectAfterClipRRect = false;
+    for (int i = 0; i < canvas.invocations.length - 1; i += 1) {
+      if (canvas.invocations[i].memberName == #clipRRect && canvas.invocations[i + 1].memberName == #drawRect) {
+        hasDrawRectAfterClipRRect = true;
+        break;
+      }
+    }
+
+    expect(hasDrawRectAfterClipRRect, true);
+  });
+
+  test('ShaderWarmUp.execute disposes the image and picture', () async {
+    const DefaultShaderWarmUp shaderWarmUp = DefaultShaderWarmUp();
+    late ui.Picture capturedPicture;
+    late ui.Image capturedImage;
+    debugCaptureShaderWarmUpPicture = (ui.Picture picture) {
+      capturedPicture = picture;
+      expect(picture.approximateBytesUsed, greaterThan(0));
+      return true;
+    };
+    debugCaptureShaderWarmUpImage = (ui.Image image) {
+      capturedImage = image;
+      expect(image.width, 100);
+      expect(image.height, 100);
+      return true;
+    };
+    await shaderWarmUp.execute();
+    expect(
+      () => capturedPicture.approximateBytesUsed,
+      throwsA(isA<String>().having((String message) => message, 'message', 'Object has been disposed.')),
+    );
+    expect(capturedImage.debugDisposed, true);
+  }, skip: kIsWeb); // Browser doesn't support approximateBytesUsed and doesn't rasterize the picture at this time.
+}