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

dev/tracing_tests/test/image_cache_tracing_test.dart

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

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 an instance of [DefaultShaderWarmUp].
+  /// 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.
   ///
   /// If the application has scenes that require the compilation of complex
-  /// 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.
+  /// 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.
   ///
   /// 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 = const DefaultShaderWarmUp();
+  static ShaderWarmUp? shaderWarmUp;
 
   /// The singleton that implements the Flutter framework's image cache.
   ///

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

@@ -17,12 +17,11 @@ 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. 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].
+/// 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].
 ///
 /// To determine whether a draw operation is useful for warming up shaders,
 /// check whether it improves the slowest frame rasterization time. Also,
@@ -102,141 +101,3 @@ 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

@@ -38,6 +38,10 @@ 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 {