[Impeller] add --enable-impeller-3d flag to support scene experimentation (flutter/engine#37990)

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engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -1714,6 +1714,7 @@ FILE: ../../../flutter/impeller/typographer/typographer_unittests.cc
 FILE: ../../../flutter/lib/io/dart_io.cc
 FILE: ../../../flutter/lib/io/dart_io.h
 FILE: ../../../flutter/lib/snapshot/libraries.json
+FILE: ../../../flutter/lib/snapshot/libraries_experimental.json
 FILE: ../../../flutter/lib/snapshot/snapshot.h
 FILE: ../../../flutter/lib/ui/annotations.dart
 FILE: ../../../flutter/lib/ui/channel_buffers.dart
@@ -1728,6 +1729,8 @@ FILE: ../../../flutter/lib/ui/dart_runtime_hooks.h
 FILE: ../../../flutter/lib/ui/dart_ui.cc
 FILE: ../../../flutter/lib/ui/dart_ui.h
 FILE: ../../../flutter/lib/ui/dart_wrapper.h
+FILE: ../../../flutter/lib/ui/experiments/compositing_3d.dart
+FILE: ../../../flutter/lib/ui/experiments/ui.dart
 FILE: ../../../flutter/lib/ui/geometry.dart
 FILE: ../../../flutter/lib/ui/hash_codes.dart
 FILE: ../../../flutter/lib/ui/hooks.dart

engine/src/flutter/impeller/tools/impeller.gni

@@ -35,6 +35,9 @@ declare_args() {
 
   # Call glGetError after each OpenGL call and log failures.
   impeller_error_check_all_gl_calls = is_debug
+
+  # Eperimentally enable 3d code paths.
+  impeller_enable_3d = false
 }
 
 declare_args() {

engine/src/flutter/lib/snapshot/BUILD.gn

@@ -5,6 +5,7 @@
 import("//build/compiled_action.gni")
 import("//build/fuchsia/sdk.gni")
 import("//flutter/common/config.gni")
+import("//flutter/impeller/tools/impeller.gni")
 import("//flutter/lib/ui/dart_ui.gni")
 import("//third_party/dart/utils/compile_platform.gni")
 
@@ -315,8 +316,13 @@ source_set("snapshot") {
 compile_platform("strong_platform") {
   single_root_scheme = "org-dartlang-sdk"
   single_root_base = rebase_path("../../../")
-  libraries_specification_uri =
-      "org-dartlang-sdk:///flutter/lib/snapshot/libraries.json"
+  if (impeller_enable_3d) {
+    libraries_specification_uri =
+        "org-dartlang-sdk:///flutter/lib/snapshot/libraries_experimental.json"
+  } else {
+    libraries_specification_uri =
+        "org-dartlang-sdk:///flutter/lib/snapshot/libraries.json"
+  }
 
   outputs = [
     "$root_out_dir/flutter_patched_sdk/platform_strong.dill",

engine/src/flutter/lib/snapshot/libraries_experimental.json

@@ -0,0 +1,17 @@
+{
+    "comment:0": "NOTE: THIS FILE IS GENERATED. DO NOT EDIT.",
+    "comment:1": "Instead modify 'flutter/lib/snapshot/libraries.yaml' and follow the instructions therein.",
+    "flutter": {
+      "include": [
+        {
+          "path": "../../../third_party/dart/sdk/lib/libraries.json",
+          "target": "vm_common"
+        }
+      ],
+      "libraries": {
+        "ui": {
+          "uri": "../../lib/ui/experiments/ui.dart"
+        }
+      }
+    }
+  }

engine/src/flutter/lib/ui/BUILD.gn

@@ -189,6 +189,9 @@ source_set("ui") {
     # Required for M_PI and others.
     defines += [ "_USE_MATH_DEFINES" ]
   }
+  if (impeller_enable_3d) {
+    defines += [ "IMPELLER_ENABLE_3D" ]
+  }
 }
 
 if (enable_unittests) {

engine/src/flutter/lib/ui/compositing/scene_builder.cc

@@ -262,6 +262,22 @@ void SceneBuilder::addTexture(double dx,
   AddLayer(std::move(layer));
 }
 
+#ifdef IMPELLER_ENABLE_3D
+// static
+void SceneBuilder::addModelLayer(Dart_Handle wrapper,
+                                 double dx,
+                                 double dy,
+                                 double width,
+                                 double height,
+                                 int64_t viewId) {
+  auto* scene_builder = tonic::DartConverter<SceneBuilder*>::FromDart(wrapper);
+  SkMatrix sk_matrix = SkMatrix::Translate(dx, dy);
+  auto layer = std::make_shared<flutter::TransformLayer>(sk_matrix);
+  scene_builder->AddLayer(std::move(layer));
+}
+
+#endif  // IMPELLER_ENABLE_3D
+
 void SceneBuilder::addPlatformView(double dx,
                                    double dy,
                                    double width,

engine/src/flutter/lib/ui/compositing/scene_builder.h

@@ -34,6 +34,15 @@ class SceneBuilder : public RefCountedDartWrappable<SceneBuilder> {
     res->AssociateWithDartWrapper(wrapper);
   }
 
+#ifdef IMPELLER_ENABLE_3D
+  static void addModelLayer(Dart_Handle wrapper,
+                            double dx,
+                            double dy,
+                            double width,
+                            double height,
+                            int64_t viewId);
+#endif  // IMPELLER_ENABLE_3D
+
   ~SceneBuilder() override;
 
   void pushTransformHandle(Dart_Handle layer_handle,

engine/src/flutter/lib/ui/dart_ui.cc

@@ -294,6 +294,10 @@ typedef CanvasPath Path;
   V(SemanticsUpdate, dispose, 1)                       \
   V(Vertices, dispose, 1)
 
+#ifdef IMPELLER_ENABLE_3D
+#define FFI_METHOD_LIST_3D(V) V(SceneBuilder::addModelLayer, 7)
+#endif  // IMPELLER_ENABLE_3D
+
 #define FFI_FUNCTION_INSERT(FUNCTION, ARGS)     \
   g_function_dispatchers.insert(std::make_pair( \
       std::string_view(#FUNCTION),              \
@@ -320,6 +324,9 @@ void* ResolveFfiNativeFunction(const char* name, uintptr_t args) {
 void InitDispatcherMap() {
   FFI_FUNCTION_LIST(FFI_FUNCTION_INSERT)
   FFI_METHOD_LIST(FFI_METHOD_INSERT)
+#ifdef IMPELLER_ENABLE_3D
+  FFI_METHOD_LIST_3D(FFI_FUNCTION_INSERT)
+#endif  // IMPELLER_ENABLE_3D
 }
 
 }  // anonymous namespace

engine/src/flutter/lib/ui/experiments/compositing_3d.dart

@@ -0,0 +1,18 @@
+// Copyright 2013 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.
+part of dart.ui;
+
+void addModelLayer(
+  SceneBuilder builder,
+  int viewId, {
+  Offset offset = Offset.zero,
+  double width = 0.0,
+  double height = 0.0,
+}) {
+  assert(offset != null, 'Offset argument was null');
+  _addModelLayer(builder, offset.dx, offset.dy, width, height, viewId);
+}
+
+@FfiNative<Void Function(Handle, Double, Double, Double, Double, Int64)>('SceneBuilder::addModelLayer')
+external void _addModelLayer(Object object, double dx, double dy, double width, double height, int viewId);

engine/src/flutter/lib/ui/experiments/ui.dart

@@ -0,0 +1,43 @@
+// Copyright 2013 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.
+
+/// Built-in types and core primitives for a Flutter application.
+///
+/// To use, import `dart:ui`.
+///
+/// This library exposes the lowest-level services that Flutter frameworks use
+/// to bootstrap applications, such as classes for driving the input, graphics
+/// text, layout, and rendering subsystems.
+library dart.ui;
+
+import 'dart:async';
+import 'dart:collection' as collection;
+import 'dart:convert';
+import 'dart:developer' as developer;
+import 'dart:ffi';
+import 'dart:io';
+import 'dart:isolate' show SendPort;
+import 'dart:math' as math;
+import 'dart:nativewrappers';
+import 'dart:typed_data';
+
+part '../annotations.dart';
+part '../channel_buffers.dart';
+part '../compositing.dart';
+part 'compositing_3d.dart';
+part '../geometry.dart';
+part '../hash_codes.dart';
+part '../hooks.dart';
+part '../isolate_name_server.dart';
+part '../key.dart';
+part '../lerp.dart';
+part '../math.dart';
+part '../natives.dart';
+part '../painting.dart';
+part '../platform_dispatcher.dart';
+part '../plugins.dart';
+part '../pointer.dart';
+part '../semantics.dart';
+part '../text.dart';
+part '../window.dart';

engine/src/flutter/tools/gn

@@ -551,6 +551,9 @@ def to_gn_args(args):
   elif os.getenv('FLUTTER_IMPELLER_ENABLE_PLAYGROUND', '0') == '1':
     gn_args['impeller_enable_playground'] = True
 
+  if args.enable_impeller_3d:
+    gn_args['impeller_enable_3d'] = True
+
   if args.prebuilt_impellerc is not None:
     gn_args['impeller_use_prebuilt_impellerc'] = args.prebuilt_impellerc
 
@@ -978,6 +981,13 @@ def parse_args(args):
       'https://github.com/flutter/flutter/issues/107357'
   )
 
+  parser.add_argument(
+      '--enable-impeller-3d',
+      default=False,
+      action='store_true',
+      help='Enables experimental 3d support.'
+  )
+
   # Sanitizers.
   parser.add_argument('--asan', default=False, action='store_true')
   parser.add_argument('--lsan', default=False, action='store_true')